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Tuesday, 13 December 2016

The Condor Volume 118 Issue 4 November 2016

The Condor
Published by: American Ornithological Society

Table of Contents
Nov 2016 : Volume 118 Issue 4 



Nesting habitat selection influences nest and early offspring survival in Greater Sage-Grouse
Daniel Gibson, Erik J. Blomberg, Michael T. Atamian and James S. Sedinger

Adaptive habitat-selection theory predicts that individuals should use habitats that maximize lifetime fitness. However, trade-offs between life-history stages, environmental variability, and predator–prey dynamics can interact with individual preferences, which may result in individuals selecting suboptimal habitats. Understanding the distinction between adaptive and maladaptive animal use of habitat is central to effective species conservation, because use of maladaptive habitat is counter to conservation objectives. Our objectives were to assess whether habitat characteristics selected by Greater Sage-Grouse (Centrocercus urophasianus) were correlated with increased production of fledged young. We monitored 411 nests and 120 broods from 234 females between 2004 and 2012 in central Nevada, USA. We determined which habitat characteristics were selected as nesting habitat and assessed whether these characteristics influenced nest success and early offspring survival. The relationships between characteristics selected at nest sites and metrics of reproductive success were variable, in that certain characteristics (e.g., forb cover, amount of pinyon–juniper woodlands) were correlated with higher nest survival and chick survival, but other characteristics (e.g., amount of sagebrush, residual grass height) did not improve reproductive success. Despite variability among predictor variables, we found a positive effect of selection of fine-scale habitat characteristics on nest (βNS-Local = 0.14, 85% confidence interval [CI]: 0.04–0.23) and chick survival (βCS-Local = 0.39, 85% CI: 0.27–0.50); however, we did not find that selection of broad-scale habitat characteristics predicted reproductive success (βNS-Landscape = −0.04, 85% CI: −0.15 to 0.06; βCS-Landscape = 0.06, 85% CI: −0.06 to 0.18). Additionally, nest-site selection was more predictive of chick survival than of nest survival, which suggests that females' selection of nesting habitat was based primarily on its qualities as brood-rearing habitat. Together, these findings suggest that nest-site selection may be influenced by more than increased reproductive success, or that there is a landscape-level pattern to local-scale habitat characteristics.

Ancient DNA reveals substantial genetic diversity in the California Condor (Gymnogyps californianus) prior to a population bottleneck
Jesse D'Elia, Susan M. Haig, Thomas D. Mullins and Mark P. Miller

Critically endangered species that have undergone severe population bottlenecks often have little remaining genetic variation, making it difficult to reconstruct population histories to apply in reintroduction and recovery strategies. By using ancient DNA techniques, it is possible to combine genetic evidence from the historical population with contemporary samples to provide a more complete picture of a species' genetic variation across its historical range and through time. Applying this approach, we examined changes in the mitochondrial DNA (mtDNA) control region (526 base pairs) of the endangered California Condor (Gymnogyps californianus). Results showed a >80% reduction in unique haplotypes over the past 2 centuries. We found no spatial sorting of haplotypes in the historical population; the periphery of the range contained haplotypes that were common throughout the historical range. Direct examination of mtDNA from California Condor museum specimens provided a new window into historical population connectivity and genetic diversity showing: (1) a substantial loss of haplotypes, which is consistent with the hypothesis that condors were relatively abundant in the nineteenth century, but declined rapidly as a result of human-caused mortality; and (2) no evidence of historical population segregation, meaning that the available genetic data offer no cause to avoid releasing condors in unoccupied portions of their historical range.

Minimal bias in surveys of grassland birds from roadsides
Christopher M. Lituma and David A. Buehler

Edges, including roads, can have unintended deleterious impacts on wildlife. However, roads also present opportunities for replicable, and spatially and temporally consistent, wildlife monitoring. Assessing sources of variability associated with roadside-based surveys could improve the accuracy and extend the inferences of surveys, thus strengthening their applicability to management. We assessed roadside effects on abundance (λ) and detection probability (p) of high-priority grassland and shrubland songbirds in western Kentucky and Tennessee, USA. We delineated transects 300 m apart perpendicular to secondary roads and, along each transect, positioned point counts at 0 m, 300 m, and 600 m off the road. We surveyed 8 species: Northern Bobwhite (Colinus virginianus), Bell's Vireo (Vireo bellii), Prairie Warbler (Setophaga discolor), Field Sparrow (Spizella pusilla), Grasshopper Sparrow (Ammodramus savannarum), Henslow's Sparrow (Ammodramus henslowii), Dickcissel (Spiza americana), and Eastern Meadowlark (Sturnella magna). We used Royle N-Mixture models to estimate species-specific abundance and detection probability. For abundance, distance from the road affected only Henslow's Sparrow; mean Henslow's Sparrow abundance increased by 59% at points 600 m away from a road. For detection probability, distance from the road was not important for any species, suggesting that noise or activity associated with low-traffic roads did not affect bird singing behavior or observer hearing ability enough to affect survey results. Abundance was more strongly related to land-cover covariates than distance from the road. With the exception of Henslow's Sparrow, roadside surveys for 8 high-priority grassland bird species produced estimates of abundance and detection probabilities representative of the broader landscape. Roads can provide opportunities to accurately monitor occupancy, abundance, and density of grassland birds using surveys that account for land-cover variation and seasonal variation in detection probability.

Interactive effects between nest microclimate and nest vegetation structure confirm microclimate thresholds for Lesser Prairie-Chicken nest survival
Blake A. Grisham, Alixandra J. Godar, Clint W. Boal and David A. Haukos

The range of Lesser Prairie-Chickens (Tympanuchus pallidicinctus) spans 4 unique ecoregions along 2 distinct environmental gradients. The Sand Shinnery Oak Prairie ecoregion of the Southern High Plains of New Mexico and Texas is environmentally isolated, warmer, and more arid than the Short-Grass, Sand Sagebrush, and Mixed-Grass Prairie ecoregions in Colorado, Kansas, Oklahoma, and the northeast panhandle of Texas. Weather is known to influence Lesser Prairie-Chicken nest survival in the Sand Shinnery Oak Prairie ecoregion; regional variation may also influence nest microclimate and, ultimately, survival during incubation. To address this question, we placed data loggers adjacent to nests during incubation to quantify temperature and humidity distribution functions in 3 ecoregions. We developed a suite of a priori nest survival models that incorporated derived microclimate parameters and visual obstruction as covariates in Program MARK. We monitored 49 nests in Mixed-Grass, 22 nests in Sand Shinnery Oak, and 30 nests in Short-Grass ecoregions from 2010 to 2014. Our findings indicated that (1) the Sand Shinnery Oak Prairie ecoregion was hotter and drier during incubation than the Mixed- and Short-Grass ecoregions; (2) nest microclimate varied among years within ecoregions; (3) visual obstruction was positively associated with nest survival; but (4) daily nest survival probability decreased by 10% every half-hour when temperature was greater than 34°C and vapor pressure deficit was less than −23 mmHg during the day (about 0600–2100 hours). Our major finding confirmed microclimate thresholds for nest survival under natural conditions across the species' distribution, although Lesser Prairie-Chickens are more likely to experience microclimate conditions that result in nest failures in the Sand Shinnery Oak Prairie ecoregion. The species would benefit from identification of thermal landscapes and management actions that promote cooler, more humid nest microclimates.

Meta-analysis of California Spotted Owl (Strix occidentalis occidentalis) territory occupancy in the Sierra Nevada: Habitat associations and their implications for forest management 
Douglas J. Tempel, John J. Keane, R. J. Gutiérrez, Jared D. Wolfe, Gavin M. Jones, Alexander Koltunov, Carlos M. Ramirez, William J. Berigan, Claire V. Gallagher, Thomas E. Munton, Paula A. Shaklee, Sheila A. Whitmore and M. Zachariah Peery

We assessed the occupancy dynamics of 275 California Spotted Owl (Strix occidentalis occidentalis) territories in 4 study areas in the Sierra Nevada, California, USA, from 1993 to 2011. We used Landsat data to develop maps of canopy cover for each study area, which we then used to quantify annual territory-specific habitat covariates. We modeled the relationships between territory extinction and colonization using predictor variables of habitat, disturbance (logging, fire), climate, and elevation. We found that forests with medium (40–69%) and high (≥70%) canopy cover were the most important predictors of territory occupancy in all study areas, and that both canopy cover categories were positively correlated with occupancy. We used analysis of deviance to estimate the amount of variation explained by the habitat covariates (primarily medium and high canopy cover) and found that these covariates explained from 35% to 67% of the variation in occupancy. Climatic covariates were not correlated with occupancy dynamics and explained little of the variation in occupancy. We also conducted a post hoc analysis in which we partitioned canopy cover into 10% classes, because our original partitioning into 3 classes may have lacked sufficient resolution to identify canopy cover levels where occupancy changed abruptly. In this post hoc analysis, occupancy declined sharply when territories contained more area with <40% canopy cover, and the amount of 50–59% and 60–69% canopy cover had a more positive association with occupancy than did 40–49% canopy cover. Our results suggest that some fuels treatments intended to reduce fire risk and improve forest resilience could be located within Spotted Owl territories without adversely impacting territory occupancy if such treatments do not consistently reduce canopy cover below 50%. We suggest that future work quantify components of forest structure (e.g., large tree density, vertical complexity) known to be selected by owls and relate these characteristics to occupancy and fitness metrics.

Transferability of habitat suitability models for nesting woodpeckers associated with wildfire
Quresh S. Latif, Victoria A. Saab, Jeff P. Hollenbeck and Jonathan G. Dudley

Following wildfire, forest managers are challenged with meeting both socioeconomic demands (e.g., salvage logging) and mandates requiring habitat conservation for disturbance-associated wildlife (e.g., woodpeckers). Habitat suitability models for nesting woodpeckers can be informative, but tests of model transferability are needed to understand how broadly models developed at one location can be applied to inform post-fire forest management at other locations. We developed habitat suitability models and tested their transferability for 2 disturbance-associated woodpecker species, Black-backed (Picoides arcticus) and Lewis's (Melanerpes lewis) woodpecker. Habitat suitability models consisted of weighted logistic regression models comparing environmental conditions at nest versus non-nest sites. We developed models at each of 3 wildfire locations in Washington, Oregon, and Idaho, and then examined predictive performance for each model at alternate (“application”) locations. Models generally discriminated nest from non-nest sites well at locations where they were developed but performance was variable at application locations, indicating limited transferability. Models for Black-backed Woodpecker and those that included field-collected environmental covariates exhibited greater transferability than models for Lewis's Woodpecker and those that only included remotely sensed covariates. Transferability was also generally poor between Oregon and the other 2 locations. Limitations to model transferability observed in this study suggest models developed at any one wildfire location are unlikely to be generally applicable across the entire range of Black-backed and Lewis's woodpeckers. Generally applicable models to inform post-fire forest management will therefore likely require integration of data from multiple wildfire locations.

Density and microhabitat preference of the Southern Bristle-Tyrant (Phylloscartes eximius): Conservation policy implications
Vinicius R. Tonetti and Marco A. Pizo

Demographic and habitat preference studies are of paramount importance for conservation of birds, which is urgent in the mostly devastated Atlantic Forest. Moreover, these studies can indicate microhabitats that deserve more attention for conservation. In this article, we provide the first population density estimate and microhabitat preference assessment for the Southern Bristle-Tyrant (Phylloscartes eximius), a poorly known and threatened insectivorous bird endemic to the Atlantic Forest. The study was conducted at Cantareira State Park between May and December 2014. For density estimates we sampled 600 point counts using distance sampling, and for microhabitat assessment we compared 15 variables in 54 plots where birds were observed foraging with 145 random plots by adjusting generalized linear models and using hierarchical partitioning analysis. The species' density (12.7 [7.3–20.2] individuals per km2) is ∼1/16 the density of a globally threatened congener, the Restinga Tyrannulet (Phylloscartes kronei), and lower than most other small insectivorous passerines in Atlantic Forest. When alone or in pairs, Southern Bristle-Tyrants preferred forests within ∼10m of rivers and lakes; when in mixed-species flocks they preferred valleys (grotas). We suggest that protection of riverine forests would benefit Southern Bristle-Tyrants with positive consequences for the water supply of millions of people living in the Atlantic Forest domain.

Juvenile survival, recruitment, population size, and effects of avian pox virus in Laysan Albatross (Phoebastria immutabilis) on Oahu, Hawaii, USA
Eric A. VanderWerf and Lindsay C. Young

Understanding population dynamics and determining conservation priorities in long-lived species with delayed breeding often is hampered by lack of information about younger age classes. Obtaining accurate estimates of juvenile survival and recruitment can be difficult because young individuals are infrequently observed. We used mark–recapture models to estimate age-specific survival, recruitment, population size, and encounter probability of Laysan Albatrosses (Phoebastria immutabilis) using a 14-yr dataset from Oahu, Hawaii, USA. We also measured the long-term effect of avian pox virus (Poxvirus avium) on the survival and recruitment of albatrosses infected as nestlings. Survival of juvenile albatrosses during the first year after fledging was 0.757 ± 0.042. We were able to estimate juvenile survival, the first such estimate in any long-lived seabird, because our high search effort revealed that some birds began visiting the natal colony at the age of 1 yr. The survival of prebreeders increased rapidly and reached a value in the second year (0.973 ± 0.008) that was similar to the survival of breeding adults (0.973 ± 0.017). The average age of first return to the natal colony was 4.24 ± 0.11 yr. The average age at first breeding was 8.44 ± 0.15 yr, with recruitment probability peaking at ages 9–10 yr and a single bird being recruited into the breeding population at the age of 4 yr. Pox virus decreased survival in the first year by 4%–13% and decreased recruitment probability up to age 12 by 4%–26%, depending on the severity of infection. The total size of the Laysan Albatross population on Oahu in 2015 was 555 birds, consisting of 270 active breeders, 231 prebreeders, and 54 birds that likely skipped breeding that year. The number of prebreeders constituted an average of 44% of the total population. These demographic estimates will be useful for population modeling exercises involving various threat and management scenarios, and for examining environmental factors that influence demography.

Reproductive success of songbirds and waterfowl in native mixed-grass pasture and planted grasslands used for pasture and hay
Stephen K. Davis, Sarah M. Ludlow and D. Glen McMaster

Conservation of grassland birds in agricultural landscapes requires an understanding of the demographic consequences of nesting in native and planted grasslands. Much of the native grassland in agricultural regions has been converted to cropland. Subsequently, seeding cropland to perennial grasslands has become a common strategy to restore habitat for grassland birds, but these grasslands also may be used as hay and pasture forage for livestock. Our objectives were to determine (1) if the abundance of grassland songbirds and the reproductive success of songbirds and waterfowl varied between native pasture and planted grassland, and (2) if the amount of grassland in the surrounding landscape influenced the abundance and reproductive success of songbirds or the nest survival of waterfowl in native and planted grasslands. Our results suggest that planted grasslands used for pasture and hay in our region are likely ecological sinks for grassland specialist songbirds. Sprague's Pipit (Anthus spragueii) nested only in native pasture, and Chestnut-collared Longspur (Calcarius ornatus), Lark Bunting (Calamospiza melanocorys), and Baird's Sparrow (Ammodramus bairdii) were sometimes more abundant in planted pasture or hayfields, but fledged 1.4–4.5 times as many young per nest in native pasture. The reproductive success of waterfowl and grassland songbird generalists was similar in planted grasslands and native pasture. The abundance of all songbirds varied with the amount of grassland or cropland in the surrounding landscape, but landscape composition only weakly influenced the nest survival rates of 1 of 8 songbirds and 4 of 6 waterfowl species. Our results demonstrate that the preservation of native pasture is critical for the conservation of grassland specialists. Other grassland songbirds and waterfowl likely will benefit from the conservation of native and planted grassland and conversion of cropland to perennial grassland used for pasture and hay.

Geolocator tracking of Great Reed-Warblers (Acrocephalus arundinaceus) identifies key regions for migratory wetland specialists in the Middle East and sub-Saharan East Africa
Joshua J. Horns, Evan Buechley, Mark Chynoweth, Lale Aktay, Emrah Çoban, Mehmet Ali Kırpık, Jordan M. Herman, Yakup Şaşmaz and Çağan H. Şekercioğlu

Wetland-dependent migratory songbirds represent one of the most vulnerable groups of birds on the planet, with >67% of wetland-obligate species threatened with extinction. One of the major hurdles for conservation efforts is determining the migration routes, stopover sites, and wintering sites of these species. We describe an annual migration cycle revealed by geolocator tracking of Great Reed-Warblers (Acrocephalus arundinaceus) breeding in the Aras River wetlands of eastern Turkey. Because of its relatively large size and breeding ground fidelity, the Great Reed-Warbler is an excellent candidate for geolocator studies and can serve as an indicator species for other wetland songbirds, many of which are particularly threatened in the Middle East. All birds made use of at least 2 wintering grounds in South Sudan, on the Indian Ocean coast and on the western shores of Lake Malawi, as well as several important stopover sites. We also identified a counterclockwise migration path into and out of Africa. Throughout the year, these birds encountered 277 Important Bird Areas, >40% of which had little or no protection. Many species of wetland songbird, particularly threatened species, may be too rare or too small to be the focus of similar studies. Our results not only allow for comparisons with other Great Reed-Warbler populations, but also reveal previously unknown stopover and wintering locations to target conservation efforts that will help wetland-dependent bird species in the Middle East and East Africa.

Nest survival of Tricolored Blackbirds in California's Central Valley
Kelly Weintraub, T. Luke George and Stephen J. Dinsmore

The Tricolored Blackbird (Agelaius tricolor), almost entirely restricted to California, USA, has recently been proposed for listing under the U.S. Endangered Species Act. Tricolored Blackbirds historically nested in wetlands, but a large proportion of the population now nests in agricultural grain fields where the crop is ready to harvest before the young have fledged. Since 1991, federal agencies have paid farmers to delay harvesting in an effort to increase nesting productivity. However, the relative nesting success of Tricolored Blackbirds breeding in agricultural fields versus wetlands is unknown. Our objectives were to estimate daily survival rate (DSR) of nests, identify habitat covariates that influence nest survival, and estimate the number of young produced per nest. During 2011–2012, we monitored 1,323 Tricolored Blackbird nests in 12 colonies using small temperature data loggers. We modeled DSR using Program RMark with combinations of the following variables: site, habitat type, nest initiation date, nest height, water depth, nest density, colony population size, year, and the proportion of nearby nests that failed. Nest survival varied greatly (range: 0.024–0.719) but was not explained by habitat type. Nest height and nest density were positively associated with DSR. DSR was lowest midway through the breeding season and declined with colony population size. Number of young produced per nest varied by site, was lowest in intermediate-sized colonies of 1,000–5,000 birds, and was highest in 2011. DSR and number of young fledged per nest were similar in agricultural fields and in wetlands. Our results suggest that Tricolored Blackbirds benefit from policies that allow them to complete their nesting cycle in agricultural fields.

Friday, 9 September 2016

Journal of Raptor Research, September 2016 : Volume 50 Issue 3

Journal of Raptor Research
Published by: The Raptor Research Foundation

Table of Contents
September 2016 : Volume 50 Issue 3 

Reproductive Success of Eurasian Eagle-Owls in Wetland and Non-wetland Habitats of West-central Korea
Dong-Man Shin and Jeong-Chil Yoo

The breeding success of raptors is strongly affected by food supply. We examined the reproductive success of Eurasian Eagle-Owls (Bubo bubo) and assessed the effects of landscape and diet on reproductive success at 44 nest sites in wetland and non-wetland (mostly agricultural lands, forests, and human settlements) habitats in west-central Korea. We found that eagle-owl reproductive success was significantly higher in wetland than in non-wetland habitats (mean of 1.9 vs. 1.3 fledglings per breeding pair, respectively). Although the average number of fledglings per successful pair was similar in the two habitats (2.0 vs. 1.8), the average numbers of fledglings per hatchling (0.9 vs. 0.7) and per egg (0.8 vs. 0.5) were both higher in wetland habitats. Further, for the wetland habitats, birds (mostly Anatidae, Columbidae, and Phasianidae) were the most important prey group by both number and biomass (67% and 84%, respectively) in the breeding period. However, in non-wetland habitats, both mammals (59% by number) and birds (67% by biomass) were important prey in the breeding period. The amount of Phasianidae in the diet (by biomass) and the date of the onset of egg-laying were positively and negatively (respectively) significant determinants of the number of fledglings per egg, whereas the percentage of wetland in the habitat was the only significant determinant for the number of fledglings per hatchling.

Observations of Migrating Golden Eagles (Aquila chrysaetos) in Eastern Interior Alaska Offer Insights On Population Size and Migration Monitoring
Carol L. McIntyre and Stephen B. Lewis

Migratory Golden Eagles (Aquila chrysaetos) from Alaska winter across a vast region of western North America, much of which is undergoing rapid change from a diversity of indirect and direct human activities. To address recent conservation concerns, we are studying the year-round movements of migratory Golden Eagles from interior and northern Alaska to identify and evaluate potential risks to their survival. We are also developing new survey techniques to estimate population size and trends. As part of our ongoing studies, we observed migrating Golden Eagles in spring and autumn 2014 during field investigations to locate Golden Eagle capture sites in eastern interior Alaska, and in spring 2015 during capture activities. We observed large numbers of Golden Eagles in both spring and autumn, suggesting that the Mentasta Mountains are an important migration corridor for this species. Further, our observations, including 1364 migrating Golden Eagles in October 2014, suggested that the Alaska Golden Eagle population is much larger than is reflected in the only currently available statewide population estimate of 2400 eagles. In combination with historical and contemporary tracking studies, our observations in the Mentasta Mountains provide important new information about Golden Eagle migration in Alaska and stimulate interest in answering fundamental questions about using counts of migrating Golden Eagles to estimate, and detect change in, the population size of Alaska's migratory Golden Eagles. Our observations also provide new information about Rough-legged Hawk migration in Alaska.

Retention, Effect, and Utility of Tail-mounted Satellite-tracked Transmitters on Golden Eagles
Alan R. Harmata

Studies deploying Platform Transmitter Terminals (PTTs) or Global System for Mobile Communications-GPS (GSM) packages on Golden Eagles have typically used backpack harnesses for attachment despite evidence indicating potential significant negative effects on reproduction and survival. Retention, safety, and utility of tail-mounted PTTs were tested on a sample of Golden Eagles in southwestern Montana. Argos satellite-tracked PTTs of two configurations were attached dorsally or ventrally to the central rectrices of 27 Golden Eagles to study survival. Sixteen packages were known to have been molted or removed (i.e., shed) by the eagle and 13 recovered. Of recovered tail-mounts, six (46%) were forcibly removed by eagles; five by males and one by a female. All packages that were forcibly removed were 32-g ventral mounts. Females tended to retain tail-mounts longer than males and dorsally mounted PTTs tended to be retained longer than those mounted ventrally. Eagles tagged in winter retained PTTs the longest. The duration of tail-mounted PTT retention was adequate for analysis of survival and yielded an adult annual survival rate (86%) consistent with recent U.S. Fish and Wildlife Service estimates (87%). Eight of 13 (62%) territorial adults tagged with PTTs were known to attempt breeding the year they were tracked and six (46%) produced young, rates that did not differ (P > 0.23) from those of a larger sample of the population surveyed during the same period. Logistic regression analysis of cumulative range size by monitoring duration of four territorial adult eagles with tail-mounted GPS indicated that 99% of total range was recorded within 140 d of tracking.

Temporal and Spatial Dietary Variation of Amur Falcons (Falco amurensis) in their South African Nonbreeding Range 
Jarryd Alexander and Craig T. Symes

We studied the spatial and temporal dietary patterns of the Amur Falcon (Falco amurensis), a nonbreeding Palearctic migrant to South Africa, by collecting regurgitated pellets at two large colonial roost sites, i.e., Middelburg and Newcastle, over 11 equal sampling periods during December 2012 to March 2013. We dried the pellets to constant mass and classified the prey items to the lowest taxonomic level possible. Amur Falcons fed mainly on invertebrates (seven orders), and occasionally on vertebrates (three orders). The five most abundant prey taxa (pooled for both sites) were; Coleoptera, Orthoptera, Isoptera, Solifugae, and Hymenoptera. Lepidoptera, Hemiptera, Passeriformes, Rodentia, and Soricomorpha were consumed almost 20 times less frequently. Isoptera, Hymenoptera, Lepidoptera, and Rodentia were consumed significantly more frequently at Middelburg, while Orthoptera and Solifugae were consumed more frequently at Newcastle. The consumption of Coleoptera did not differ significantly between sites but decreased through the season, being most important when falcons arrived in South Africa in December. Consumption of Orthoptera increased through the season and was greatest prior to migration. The percentages of Isoptera and Hymenoptera in the diet peaked at different periods, likely the result of prey population irruptions. Diet similarity of sample periods between sites ranged from 33.3–100% (mean = 69.5%), and within-site similarity among sample periods ranged from 50–100% (mean = 75.6%) and 37.5–100% (mean = 65.9%) for Newcastle and Middelburg, respectively. This study highlights the variable importance of specific prey taxa, predominantly invertebrates, for Amur Falcons during the overwintering period in South Africa.

Seroprevalence of Avian Pox and Mycoplasma gallisepticum in Raptors in Central Illinois
Elizabeth R. Wrobel, Travis E. Wilcoxen, Jacques T. Nuzzo and Jane Seitz

We assessed prevalence of the bacterium Mycoplasma gallisepticum and virus Avipoxvirus in seven species of raptors admitted to the Illinois Raptor Center from 1 January 2014 to 1 September 2015. We used visual identification of pathology to diagnose current infections and enzyme-linked immunosorbent assays (ELISA) for avian IgY antibodies against each pathogen to determine infection history of the birds. Seroprevalence of IgY against each pathogen differed significantly among species. Species that commonly prey upon birds had a greater prevalence of antibodies against each pathogen. Our finding of infrequent physical signs of disease, but frequent antibody presence, suggests that although exposure to each of these pathogens is not a rare occurrence, these raptors are capable of mounting an effective adaptive immune response and preventing development of pathology in most cases.


A Comparison of Nest Survival Between Cliff- and Tree-nesting Golden Eagles
Ross H. Crandall, Derek J. Craighead and Bryan E. Bedrosian

Morphometric Sex Determination of After-hatch-year Bald Eagles in Louisiana
Nickolas R. Smith, Alan D. Afton and Thomas J. Hess,Jr.

Body Mass of Female Cooper's Hawks is Unrelated to Longevity and Breeding Dispersal: Implications for the Study of Breeding Dispersal 
Robert N. Rosenfield, John Bielefeldt, Taylor G. Haynes, Madeline G. Hardin, Frederick J. Glassen and Travis L. Booms


First Record of Peregrine Falcon (Falco peregrinus) Ground Nesting Activity on the U.S. Atlantic Coast
Ruth Boettcher and Elizabeth K. Mojica

Long-term Occupancy (1900–2015) of an Egyptian Vulture Nest 
Juan Ramírez, Julio Roldan, Manuel de la Riva and José A. Donázar

Predation of Dawn-swarming Bats by Eurasian Hobby (Falco subbuteo) 
David J. Stanton

Aerial Rolling Behavior by a Crested Caracara (Caracara cheriway) 
Daniel M. Brooks and Steven G. Mayes

Evidence of an Urban Peregrine Falcon (Falco peregrinus) Feeding Young at Night
Esther F. Kettel, Louise K. Gentle and Richard W. Yarnell

Tuesday, 19 July 2016

The Auk July 2016: Volume 133, Issue 3

The Auk
Published by: The American Ornithologists' Union

July 2016 : Volume 133 Issue 3 


A quantitative analysis of objective feather color assessment: Measurements in the laboratory do not reflect true plumage color 
Iker Vaquero-Alba, Andrew McGowan, Daniel Pincheira-Donoso, Matthew R. Evans and Sasha R. X. Dall

An important driver of the evolution of animal coloration is sexual selection operating on traits that are used to transmit information to rivals and potential mates, which has a major impact on fitness. Reflectance spectrometry has become a standard color-measuring tool, especially after the discovery of tetrachromacy in birds and their ability to detect UV light. Birds' plumage patterns may be invisible to humans, and therefore the establishment of reliable and quantitatively objective ways of assessing coloration not dependent on human vision is a technical need of primary importance. Plumage coloration measurements can be taken directly on live birds in the field, or in the laboratory (e.g., on collected feathers). However, which of these 2 approaches offers a more reliable, repeatable sampling method remains an unsolved question. Using a spectrophotometer, we measured melanin-based coloration in the plumage of Barn Swallows (Hirundo rustica). We assessed the repeatability of measures obtained with both traditional sampling methods to quantitatively determine their reliability. We used an ANOVA-based method for calculating the repeatability of measurements from 2 years separately, and a GLMM-based method to calculate overall adjusted repeatabilities for both years. The results of our study indicate a great disparity between color measurements obtained using both sampling methods and a low comparability across them. Assuming that measurements taken in the field reflect the real or “true” color of plumage, we may conclude that there is a lack of reliability of the laboratory method to reflect this true color in melanin-based plumages. Likewise, we recommend the use of the GLMM-based statistical method for repeatability calculations, as it allows the inclusion of random factors and the calculation of more realistic, adjusted repeatabilities. It also reduces the number of necessary tests, thereby increasing power, and it allows easy calculation of 95% CIs, a measure of the reliability and precision of effect-size calculations.

Male Red-backed Fairywrens appear to enhance a plumage-based signal via adventitious molt
Samantha M. Lantz and Jordan Karubian

Phenotypically plastic signals that can be altered in response to changing environmental conditions provide animals with the ability to dynamically signal their current condition or status. Such flexibility might also provide a means of avoiding potential trade-offs between signal components. Among birds, for example, both the timing of expression and the coloration of nuptial plumage are often thought to be honest signals of condition. However, because plumage is a relatively static signal type, birds that express condition-dependent plumage signals may face a trade-off between timing of signal production and signal quality, in that signals produced relatively early may be of lower quality because of seasonal constraints. A related cost may be increased fading or wear of plumage associated with extended duration of signal expression. Male Red-backed Fairywrens (Malurus melanocephalus) exhibit asynchronous development of nuptial red–black plumage, with some individuals molting into nuptial plumage months earlier than others. We report that male Red-backed Fairywrens that molt into nuptial red–black plumage early during the nonbreeding season appear to increase their plumage coloration by replacing feathers outside of normal molt periods (i.e. adventitious molt). In this way, some male Red-backed Fairywrens may be able to molt into nuptial plumage in the nonbreeding season, which is likely to increase access to mates or resources, and to subsequently enhance the red hue of a plumage-based sexual signal to a putatively more attractive state. We suggest that adventitious molt may be a currently underappreciated mechanism that birds use to improve or maintain the quality of plumage-based signals over time, between periodic full-body molts.

Reproductive biology of the Sapayoa (Sapayoa aenigma), the “Old World suboscine” of the New World 
Sarah A. Dzielski, Benjamin M. Van Doren, Jack P. Hruska and Justin M. Hite

The Sapayoa (Sapayoa aenigma), a low-density resident of Chocó rainforests from Panama to Ecuador, has long perplexed ornithologists. It was originally described as a manakin (Pipridae), but molecular work has revealed its closest living relatives to be Old World suboscines (Eurylaimides) and supported its placement in the monotypic family of Sapayoidae. Despite such phylogenetic intrigue, little is known about the Sapayoa's general life history or reproductive biology; only one nest has been described. We present information on 2 actively attended and 13 inactive Sapayoa nests in Darién National Park, Panama. We provide the first detailed description of individual effort at an active nest, family group dynamics during the nesting period, the plumage of immature birds, and the range of vocalizations produced. We also present the first documentation of cooperative breeding and compile several recent nesting observations, extending the published Sapayoa breeding period by several months. Furthermore, we describe unusual behaviors among provisioning birds, including mounting between individuals of the same sex and mounting of a female by immature male helpers during chick provisioning. The receiving individual gave a conspicuous solicitation display before each mounting. Finally, we highlight elements of the Sapayoa's natural history that echo its Old World relatives and contrast with members of the New World Tyranni. For example, the Sapayoa resembles the eurylaimid broadbills—and differs starkly from the manakins—in diet, nest structure, breeding system, and mode of parental care.

Habitat and social factors influence nest-site selection in Arctic-breeding shorebirds
Jenny A. Cunningham, Dylan C. Kesler and Richard B. Lanctot

Habitat selection theory suggests that shorebirds should choose nest sites that maximize survival and fitness. We investigated how habitat, and proximity to conspecific or heterospecific nesting birds, was related to nest-site selection in American Golden-Plovers (Pluvialis dominica), Dunlin (Calidris alpina), Long-billed Dowitchers (Limnodromus scolopaceus), Pectoral Sandpipers (C. melanotos), Red Phalaropes (Phalaropus fulicarius), and Semipalmated Sandpipers (C. pusilla) in Barrow, Alaska, USA, between 2005 and 2012. We used remote-sensing data to link habitat information to used and unused nest sites, and we measured distances from nests to other nearby nesting shorebird neighbors. Results from an information-theoretic approach to identify best-approximating models indicated that all species selected nest sites on the basis of both habitat and social cues. Macroscale tundra moisture level within 50 m of the nest, which was closely associated with vegetation community, was an informative variable for Dunlin, Long-billed Dowitcher, and Red Phalarope, which all selected wetter habitat. Enhanced tundra microrelief increased the probability of nest-site selection for American Golden-Plover, Long-billed Dowitcher, Pectoral Sandpiper, and Semipalmated Sandpiper. American Golden-Plover, Dunlin, Pectoral Sandpiper, and Semipalmated Sandpiper selected sites farther from conspecific nests than predicted by chance. Our results indicate that shorebirds select nest sites on the basis of habitat features, and that some are also influenced by proximity to other nesting shorebirds. These findings indicate that shorebirds select nests that are likely to aid incubation abilities, reduce predator detection of nesting birds, enhance detection of predators, enhance foraging, and reduce competition from conspecifics. The variable needs of the different Arctic-breeding shorebirds indicate that climate change will have both beneficial and harmful consequences. Our habitat models may be useful for predicting areas of high shorebird importance throughout the Arctic Coastal Plain, allowing mitigation of proposed anthropogenic developments.

Effects of tidal periodicities and diurnal foraging constraints on the density of foraging wading birds
Leonardo Calle, Dale E. Gawlik, Zhixiao Xie, Lauri Green, Brian Lapointe and Allan Strong

In intertidal zones, tidal cycles reduce water depths and provide areas of shallow water where wading birds can forage for aquatic prey (water depths 0–50 cm). However, a bird that forages diurnally can make use of only a portion of the tidal cycle, which can limit fulfillment of energetic demands. Furthermore, daily and biweekly (spring–neap) tides may compound effects on shallow-water availability for foraging birds. However, the relative effects of daily and biweekly tidal periodicities on the foraging ecology of wading birds are seldom investigated due to a lack of appropriate tools. Therefore, we developed a tidal simulation model to provide dynamic spatiotemporal estimates of the availability of water depths that are within the upper and lower bounds of the birds' foraging water depth limits (“shallow-water availability”). We studied two wading bird species, the Little Blue Heron (Egretta caerulea), a daytime-only forager, and the Great White Heron (Ardea herodias occidentalis), which feeds both diurnally and nocturnally, to evaluate the relative effects of daily and biweekly tides on shallow-water availability and on patterns in abundance of foraging birds. Seasonal foraging surveys (n = 38; 2011–2013) were conducted by boat along a 14-km transect adjacent to extensive intertidal flats in the lower Florida Keys, USA. For both species combined, biweekly tides resulted in a 0.61- to 6.09-fold change in abundance, whereas daily tides resulted in a 1.03- to 5.81-fold change in abundance. Diurnal shallow-water availability was not consistently correlated in magnitude or direction with spring–neap tidal cycles because differences in tide height between consecutive low tides were larger than changes in tidal amplitude from spring–neap tide cycles. Thus, the strong response by birds to the spring–neap tide was likely driven by mechanisms other than diurnal shallow-water availability alone.

Ecomorphological differences in foraging and pattering behavior among storm-petrels in the eastern Pacific Ocean
Josh Sausner, Juan Carlos Torres-Mura, Jeanne Robertson and Fritz Hertel

For closely related species, differences in morphology can provide insight into the evolutionary history of a taxonomic group, as well as mechanisms for ecological segregation. Storm-petrels are among the smallest seabirds, and their greatest taxonomic diversity occurs in the eastern Pacific Ocean. Some storm-petrels exhibit a unique foraging behavior, known as “pattering” or “sea-anchor soaring,” in which they appear to walk on the surface of the ocean, but this behavior is used to a varying degree among species. We compared morphological traits related to the pattering behavior in 9 species of storm-petrels that breed in the eastern Pacific. Measurements on the wing (wing loading, aspect ratio), beak (size), and leg (length and foot size) were analyzed using a discriminant function analysis (DFA). A thin-plate spline/relative warp analysis was also used to detect subtle differences in wing shape. Species that patter the most have low wing loading, low foot loading, and a long tarsus and were distinct from the species that were classified as intermediate or least pattering. The DFA and a cluster analysis also identified putative pattering behavior of species based on morphology, for which there was little known observational data. A molecular phylogeny of the mitochondrial ND1 gene revealed that the 2 subfamilies of storm-petrels were not monophyletic. The phylogenetic tree shows that the pattering behavior has a strong evolutionary signal and arose early among storm-petrels.

Molecular analysis of nestling diet in a long-distance Neotropical migrant, the Louisiana Waterthrush (Parkesia motacilla)
Brian K. Trevelline, Steven C. Latta, Leesia C. Marshall, Tim Nuttle and Brady A. Porter

Elucidating the diet of Neotropical migratory birds is essential to our understanding of their ecology and to their long-term conservation. Reductions in prey availability negatively impact Neotropical migrants by affecting their survival as both nestlings and adults. Beyond broad taxonomic or morphological categories, however, the diet of Neotropical migrants is poorly documented. Using the molecular techniques of DNA barcoding and next-generation sequencing, we elucidated the diet of Louisiana Waterthrush (Parkesia motacilla) nestlings in Arkansas and Pennsylvania, USA. Waterthrush have been shown to respond negatively to the reduced availability of aquatic insects in the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT taxa). We hypothesized that Louisiana Waterthrush nestling diet would be primarily composed of these pollution-sensitive aquatic taxa, and that changes in the riparian insect community would be reflected in their diet. Unexpectedly, the orders Lepidoptera (92%) and Diptera (70%) occurred frequently in the diet of Louisiana Waterthrush nestlings. Among EPT taxa, only the order Ephemeroptera (61%) was frequently detected whereas Plecoptera (7%) and Trichoptera (1%) were poorly represented. The frequency at which aquatic Ephemeroptera and terrestrial Lepidoptera were detected in waterthrush nestling diet differed significantly over the nesting period in Pennsylvania but not in Arkansas, suggesting that phenological shifts in the availability of non-EPT prey taxa may be an important yet undescribed factor influencing the foraging ecology of waterthrush on the breeding grounds. Furthermore, these findings suggest that terrestrial insects may be more important to waterthrush nestlings than previously thought, which enhances our understanding of this biological indicator and Neotropical migrant.

Habitat quality and nest-box occupancy by five species of oak woodland birds
Megan C. Milligan and Janis L. Dickinson

Habitat quality can have important consequences for avian communities through impacts on survival and annual reproductive success. However, habitat quality is often hard to measure, leading to the use of occupancy as a proxy. We compared habitat use of 5 avian species that used nest boxes in the oak woodlands of central coastal California, USA, to determine which habitat characteristics best predicted box occupancy. We focused on the relationship between habitat characteristics and occupancy for five species—Ash-throated Flycatcher (Myiarchus cinerascens), House Wren (Troglodytes aedon), Oak Titmouse (Baeolophus inornatus), Violet-green Swallow (Tachycineta thalassina), and Western Bluebird (Sialia mexicana)—for which we had 12 consecutive years of data on nest boxes spread over a 700 ha study area. We also examined whether the physical habitat characteristics and box occupancy rates were good predictors of reproductive success, to infer whether they were useful indicators of habitat quality. The habitat characteristics influencing nest-box occupancy differed among the 5 species. Ash-throated Flycatchers were associated with fragmented habitats with less grassland. House Wrens were associated with riparian vegetation, as were Oak Titmice, which were also associated with chaparral. Violet-green Swallows were associated with chaparral but tended to nest farther from riparian corridors than Oak Titmice. Western Bluebirds nested away from riparian corridors and in areas with more grassland and oak woodland. Finally, occupancy rate was a better predictor than habitat characteristics of reproductive success, which suggests that occupancy can be a valuable proxy for habitat quality for these 5 species.

Effects of current reproductive success and individual heterogeneity on survival and future reproductive success of female Wood Ducks 
Robert A. Kennamer, Gary R. Hepp and Bradley W. Alexander

Estimates of vital rates and their sources of variation are necessary to understand the population dynamics of any organism. These data have been used to test predictions of life history theory as well as to guide decisions of wildlife managers and conservation biologists. Life history theory predicts tradeoffs among life history traits, such that current reproductive effort will be negatively correlated with survival and/or future reproduction. Many studies support this prediction, but others report positive covariation between fitness traits, and attribute positive correlations to differences in individual quality. In this study, we used 11 yr of capture–mark–recapture data of breeding female Wood Ducks (Aix sponsa), along with their breeding histories, to examine sources of variation in annual survival rates and to assess the impact of current reproductive success on probabilities of survival and future reproductive success. Cormack-Jolly-Seber models indicated that apparent survival of female Wood Ducks did not vary annually and was only weakly affected by age class and breeding habitat conditions, but that there was a strong positive relationship between survival and the number of successful nests (0, 1, or 2). Next, we used a multistate analysis to examine the importance of female nest fate (successful or failed) on the probability of surviving and of nesting successfully the next year. Early incubation body mass was used to assess the nutritional status and quality of females. Females that nested successfully in year t were not less likely to nest successfully in year t + 1 than females that had nested unsuccessfully in year t. We also found strong positive covariation between nest success in year t and the probability of surviving. However, being in relatively good or poor condition had no effect on these relationships. Our results are consistent with the idea that female quality is heterogeneous, but body mass was not a good proxy of quality. Therefore, the existence of tradeoffs between female reproductive success and survival or future reproduction was less clear because of our inability to identify and control for differences in female quality.

Target enrichment of thousands of ultraconserved elements sheds new light on early relationships within New World sparrows (Aves: Passerellidae)
Robert W. Bryson Jr., Brant C. Faircloth, Whitney L. E. Tsai, John E. McCormack and John Klicka

Sparrows in the nine-primaried oscine family Passerellidae represent an attractive model for studying avian diversification across North and South America. However, the lack of phylogenetic resolution at the base of the New World sparrow tree has hampered the use of the existing sparrow phylogeny to test questions about the evolution of sparrow traits. We generated phylogenomic data from 1,063 ultraconserved elements to estimate phylogenetic relationships among the major clades of New World sparrows. Concatenated and species-tree analyses of 271,830 base pairs of sequence data converged on a well-supported phylogeny that differs from previous estimates. The resolved backbone of the sparrow phylogeny provides new insight into the biogeography of this radiation by suggesting both a tumultuous biogeographic history, with many colonizations of South America, and several independent ecological transitions to different habitat types.

Do migratory warblers carry excess fuel reserves during migration for insurance or for breeding purposes?
Jennalee A. Holzschuh and Mark E. Deutschlander

Migration is energetically costly, and many passerines prepare for and maintain migration with hyperphagia and increased fuel or fat reserves. During spring migration, as they approach their breeding grounds, passerines may deposit fat in excess of what is needed to complete migration. Individuals may carry excess fuel reserves as insurance against potentially poor environmental conditions in early spring (insurance hypothesis). If this is true, individuals arriving early at northern stopover locations or their breeding grounds should have greater energy reserves than later arrivals. Alternatively, passerines may arrive in spring with excess fat to help offset the demands of breeding (breeding performance hypothesis). Given the energetic requirements of egg production, females may arrive with greater reserves than males if excess fat directly or indirectly offsets breeding costs. We analyzed the energetic condition of 12 warbler species mist-netted during migration from 1999 to 2012 at Braddock Bay Bird Observatory, Monroe County, New York, USA. This northern stopover location is near the breeding range (in relation to total migratory distance) for most of the parulid species we examined and, therefore, is a likely location to show carryover effects between migration and breeding. In 11 of the 12 species, energetic condition was greater in the spring than in the fall for both sexes; and in all 12 species, condition was greater in females than in males in both seasons. Contrary to the insurance hypothesis, condition increased with arrival date for most species during spring migration. Although better condition in females supports the breeding performance hypothesis, the presence of this difference in both seasons suggests that additional factors influence energetic condition in parulids. Given that males arrive in better condition in the spring than when they depart in the fall, individuals of both sexes may carry excess energy reserves during spring migration to potentially use for reproductive efforts.

Variation in egg size, shell thickness, and metal and calcium content in eggshells and egg contents in relation to laying order and embryonic development in a small passerine bird
Grzegorz Orłowski, Lucyna Hałupka, Przemysław Pokorny, Ewelina Klimczuk, Hanna Sztwiertnia and Wojciech Dobicki

Although there are quite a number of studies examining the effect of egg laying order on the levels of elements and various chemical substances, none have taken into account the presence or absence of embryonic development in the eggs. In this study, we measured the morphometry (length, breadth, volume, and mass), shell thickness, and concentrations of calcium and 10 other metals (including 8 essential elements: chromium, copper, nickel, manganese, iron, cobalt, zinc, and magnesium; and 2 nonessential elements: lead and cadmium) in the shells and contents of embryonated and nonembryonated eggs across the laying order of Eurasian Reed-Warblers (Acrocephalus scirpaceus). We found a significant increase in egg volume in both nonembryonated and embryonated eggs, and an increase in egg length and mass in embryonated eggs, with laying order. Analysis confirmed significant differences related to laying order between nonembryonated and embryonated eggs in the concentrations of elements measured in shells (Cu, Cd, Pb, Mn, Fe, and Zn) and egg contents (Pb). Analysis of the relationships between laying order and concentrations of elements revealed a significant increase in Mg and Ca concentrations in the shells of embryonated eggs, and a significant decrease in Ni in the contents of nonembryonated eggs and in Cu, Cd, Mn, and Co in the contents of embryonated eggs. Our results indicate that laying order and the presence of an embryo are critical factors responsible for variation in some features of egg morphometry and element concentrations in eggshells and egg contents. These factors should therefore be taken into consideration in studies of the chemistry and morphometry of avian eggs.

Breeding biology of the Tropeiro Seedeater (Sporophila beltoni)
Márcio Repenning and Carla Suertegaray Fontana

The recently described Tropeiro Seedeater, Sporophila beltoni, is a rare long-distance austral migrant songbird that breeds in upland grasslands of southern Brazil. No aspect of its natural history has been studied previously. We studied the natural history of this seedeater in the grasslands of the Araucarian Plateau from 2007 until 2011, focusing on breeding biology and monitoring 133 nests. The breeding cycle lasts for 3.8 months, and the breeding season is correlated with photoperiod and phenology of the grasses; nesting peaks in November and December; the mean clutch size is 2 eggs (1–3); and only the females brood, for 12 days. The nestling period lasts 10 days, and both parents care for the nestlings, although with different roles. The daily estimated survival rate (DSR) of nests, as modeled by the MARK program, was 0.94 and varied temporally in the breeding season. The estimated reproductive success was 20%. The quadratic model best explained the changes in nest survival, coupled with concealment and nest height from the ground. Other factors tested, including year-to-year variation, age of the nest, and species of support plant, did not significantly affect nest survival. Predation was the main cause of nest failure (48%), followed by desertion of nests and trampling by cattle (37%). Multiple breeding attempts (maximum 3) occurred, averaging 1.75 (SE ± 0.17) nests per female in each breeding season. This information on breeding biology and nest survival will aid in management and conservation efforts in grasslands of southern Brazil.

Phenotypic and genetic analysis support distinct species status of the Red-backed Woodpecker (Lesser Sri Lanka Flameback: Dinopium psarodes) of Sri Lanka
Saminda P. Fernando, Darren E. Irwin and Sampath S. Seneviratne

Hybridization has challenged taxonomy, since hybridizing forms could be stable evolutionary entities or ephemeral forms that are blending together. The island of Sri Lanka has 2 subspecies of the flameback woodpecker D. benghalense: D. b. jaffnense in the north and D. b. psarodes in the south. Red plumage separates the endemic phenotype D. b. psarodes from other subspecies of D. benghalense. Despite these differences, intermediate phenotypes in north-central Sri Lanka discouraged the elevation of D. b. psarodes into a full species. The recent HBW and BirdLife International checklist, however, has elevated D. b. psarodes to a full species (D. psarodes), primarily based on its plumage. To objectively evaluate whether this taxonomic elevation is warranted, we examined the phenotypic and genetic affinities of D. psarodes within the D. benghalense cluster. In doing that we provide the first quantitative phenotypic and genetic analysis across a hybrid zone for an Old World woodpecker group. We sampled woodpeckers along a line transect across the island and measured body shape/size, plumage, and genetic variation in a mitochondrial gene (Cytb). Plumage color ranged from red in the south to yellow in the north, with varying proportions of orange in north-central Sri Lanka (an area of ~66 km). Morphology (body shape/size) and plumage characters showed a clear separation. There are 2 mitochondrial haplotype groups, one in the north and one in the south. A mixture of north and south haplotypes were seen in north-central Sri Lanka. Width of the hybrid zone suggests that some form of selection limits the spread of hybrids into the range of parental forms. Morphological, plumage, and genetic traits are all indicative of limited hybridization in a narrow zone between the 2 taxa, supporting the treatment of D. psarodes as a distinct species. This study provides an illustrative example of extensive hybridization between stable taxonomic entities, discouraging the practice of merging hybridizing forms as single species.

Interspecific competition for nests: Prior ownership trumps resource holding potential for Mountain Bluebird competing with Tree Swallow 
Karen L. Wiebe

Interspecific competition over nest sites is common among cavity-nesting birds, but little is known about what determines the outcome of such contests, particularly whether or not prior ownership plays a role. Using a box removal and replacement experiment, I tested whether Mountain Bluebird (Sialia currucoides) or Tree Swallow (Tachycineta bicolor) had the higher resource holding potential (RHP). A different box-blocking experiment with paired boxes on territories measured the extent to which prior ownership influenced contest outcomes for both species. Behavioral observations in the pre-laying period showed more physical aggression by Mountain Bluebird against Tree Swallow. Nevertheless, Tree Swallow won 70% of boxes when neither species had prior ownership, suggesting Tree Swallow had a higher RHP. When their boxes were blocked, 24% of Tree Swallow usurped boxes from Mountain Bluebird, which did not differ statistically from the 33% of boxes usurped by bluebirds from swallows; thus, prior ownership does not guarantee winning the contest for either species. Currently, Mountain Bluebird arrives earlier in spring than does Tree Swallow and relies more extensively on prior ownership to retain nest sites. This advantage could be jeopardized if the migration schedule of Tree Swallow is accelerated due to climate change, and so it is important to understand the role of prior ownership in contests for nest sites for birds.

Range-wide patterns of geographic variation in songs of Golden-crowned Sparrows (Zonotrichia atricapilla)
Daizaburo Shizuka, M. Ross Lein and Glen Chilton

Discrete geographic variation, or dialects, in songs of songbirds arise as a consequence of complex interactions between ecology and song learning. Four of the five species of Zonotrichia sparrows, including the model species White-crowned Sparrow (Z. leucophrys), have been studied with respect to the causes and consequences of geographic variation in song. Within White-crowned Sparrows, subspecies that migrate farther have larger range size of dialects. Here, we assessed geographic patterns of song variation in the fifth species of this genus, the Golden-crowned Sparrow (Z. atricapilla). We analyzed field-recorded songs from 2 sampling periods (1996–1998 and 2006–2013) covering most of its breeding range in western North America. All songs began with a descending whistle and most songs consisted of 3–4 phrases that contained combinations of whistles, buzzes, and trills. We identified 13 discrete song types based on unique sequences of phrase types and frequency changes between phrases. Over 90% of individuals sang 1 of 5 song types, and we found clear dialect structure composed of these 5 common song types. The geographic range of dialects spanned large distances (500 to 1,700 km), resembling the geographic structure of dialects in the long-distance migrant Gambel's White-crowned Sparrow (Z. l. gambelli), though locations of dialect boundaries differ between species. Because both Golden-crowned Sparrows and Gambel's White-crowned Sparrows migrate similarly long distances, our study provides support to the hypothesis that dialect range size correlates with migration distance. We found little evidence of change in dialect composition in 4 populations that were sampled 15 years apart, which suggests that the dialect structure is stable across multiple generations. Our study opens the door for further comparisons to investigate links between ecology and the emergence of song dialects in this well-studied genus.

Viewing geometry affects sexual dichromatism and conspicuousness of noniridescent plumage of Swallow Tanagers (Tersina viridis)
Ana S. Barreira, Natalia C. García, Stephen C. Lougheed and Pablo L. Tubaro

Some types of plumage color are difficult to characterize spectrophotometrically because the properties of the reflected light change with viewing geometry (i.e. the relative positions of the light source and the observer, and the orientation of the feather). This is the case for the noniridescent plumage coloration of the Swallow Tanager (Tersina viridis), which seems to change from a human perspective as the angle between the light source and the observer varies. In this study, we measured plumage reflectance with different angles of illumination and/or observation, and used avian visual models to evaluate the change in sexual dichromatism and conspicuousness with viewing geometry from a bird's perspective. We also calculated different color parameters to assess how these changed with viewing conditions. Sexual dichromatism showed large changes, with its maximum coinciding with the angle combination between illuminant and observer that produced both the highest conspicuousness for males and the highest crypsis for females. The conspicuousness of males also varied with viewing geometry, and was consistently less when viewed by the visual system of a potential avian predator (VS) than by that of a conspecific (UVS). The change in perceived coloration was mainly related to large variation in hue and chroma in the plumage of males as the relative angle between the illumination and observation probes changed. Our results show that viewing geometry can alter color perception, even for noniridescent plumage coloration. Therefore, the relative position of the light source and the observer should be considered in studies of avian visual communication, particularly for species with plumage coloration similar to that of Swallow Tanagers.

Fifty-seventh Supplement to the American Ornithologists' Union
Check-list of North American Birds 
R. Terry Chesser, Kevin J. Burns, Carla Cicero, Jon L. Dunn, Andrew W. Kratter, Irby J. Lovette, Pamela C. Rasmussen, J. V. Remsen Jr., James D. Rising, Douglas F. Stotz and Kevin Winker

Tuesday, 12 July 2016

Ardeola June 2016 : Volume 63 Issue 1

Published by: Spanish Society of Ornithology/BirdLife


Table of Contents
Jun 2016 : Volume 63 Issue 1


Ardeola, a Scientific Journal of Ornithology: Cooperative Survivorship within the Red Queen Game 
Mario Díaz, Eulalia Moreno, Juan A. Amat, Beatriz Arroyo, Emilio Barba, Jacob González-Solís, Paola Laiolo, Florentino de Lope, Santiago Merino, José Ramón Obeso and Alberto Velando

Ardeola is the scientific journal of the Spanish Ornithological Society. We analyse historical changes in citation, topics and foreign authorship of articles published in Ardeola from its first publication in 1954 up to last year, 2015, to test to what extent the persistence of the journal during the last 61 years has been due to support of authors, Society members, readers, editors or the whole ornithological community. Analyses were done within the context of the Red Queen game played by scientific journals competing for the best and more cited articles. The impact factor of Ardeola has increased from 1985 onwards both in absolute and relative terms. Thematic changes have followed trends of the general ornithological literature, without the journal specialising in particular topics or geographical regions. Foreign authorship decreased from 1954 up to the end of the 20th century, subsequently increasing again, a trend fuelled by coverage by Current Contents and the JCR, the establishment of English as the language of publication and recent Internet access through the BioOne platform. Ardeola is a traditional scientific journal, backed by a scientific society, whose future will be guaranteed by a reputation for rigour and quality sought by authors, reviewers and editors, supported by the members of the Spanish Ornithological Society and retaining its original objective: ‘to be a journal at the level of the best…, looking for a strong collaboration with foreign authors to promote the benefit of the Ornithology’.


What are We Learning about Speciation and Extinction from the Canary Islands? 
Juan Carlos Illera, Lewis G. Spurgin, Eduardo Rodriguez-Exposito, Manuel Nogales and Juan Carlos Rando

Oceanic islands are excellent systems for allowing biologists to test evolutionary hypotheses due to their relative simplicity of habitats, naturally replicated study design and high levels of endemic taxa with conspicuous variation in form, colour and behaviour. Over the last two decades the Canary Islands archipelago has proved an ideal system for evolutionary biologists who seek to unravel how biodiversity arises and disappears. In this review we have evaluated the contribution of the study of Canarian birds to our understanding of how and why species occur and change over time. We focus our attention on both extant and extinct Canarian taxa, and describe how research on these species has filled gaps in our understanding of avian speciation and extinction. In addition, we discuss the necessity of revising the current taxonomy in the Canarian avian taxa, especially the status of the endemic subspecies, some of which might be better treated as full species. An accurate classification of Canarian birds is not only necessary for testing evolutionary, biogeographic and ecological hypotheses, but also for effective decision making about conservation and environmental management. Finally we introduce future avenues of research that we feel will yield the most exciting and promising findings on island evolution in the coming years.

Brood Parasite-Host Coevolution in America Versus Europe: Egg Rejection in Large-Sized Host Species
Manuel Soler

The hosts of brood parasites have evolved egg-discrimination ability as a defence that allows them to reject parasitic eggs laid in their nests. Twenty-five years ago, Stephen Rothstein emphasised that rejection rates differed markedly between potential host species in Europe and America. The much more complete information available today supports Rothstein's conclusions, but also allows new ones, especially when considering host size. For instance, successful resistance, one of the three potential long-term outcomes of brood parasite-host coevolution, is considerably more frequent in small-sized European host species and in medium-sized and large-sized Nearctic host species, while this evolutionary outcome is rare among Neotropical hosts regardless of their size. These results have never before been discussed, despite the differences being spectacular: 17 out of 19 small hosts presenting successful resistance are from Europe and 16 out of 17 medium-sized and 11 out of 13 large hosts presenting successful resistance are from North America. Interestingly, many large Nearctic hosts with a rejection rate close to 100% are corvids. The high rejection capacity shown by large Nearctic potential hosts probably evolved as a response to a highly virulent extinct brood parasite, either a large extinct cowbird or an extinct cuckoo species, which went extinct after losing the arms race against its large hosts.

The Unknown Life of Floaters: The Hidden Face of Sexual Selection 
Juan Moreno

Sexual selection, as a form of social selection based on reproductive resources, is a crucial driver of evolutionary change. Many studies on sexual selection identify potential targets only within the reproductive fraction of populations. Floaters constitute the non-territorial fraction of the population, according to the usual definitions. Floaters have been identified through exhaustive capture and marking programmes, removal and nest-box addition experiments, extra-pair paternity studies, acoustic marking and genetic studies. The literature shows that floaters may represent a considerable fraction of populations, especially among males. There is no clear evidence that size, condition or testosterone level is necessary for explaining floater status generally. However, the literature suggests that ornament size and expression are involved in territorial exclusion and may be either its cause or one of its consequences. There is some evidence that floaters survive and reproduce less well than territorials, and that changes from floater to territorial status are accompanied by changes in survival and reproductive rates. However, certain male floaters may obtain some reproductive success through extra-pair copulations. The possibility that floating constitutes a successful alternative strategy in some species cannot be excluded, although the current preliminary consensus is that floaters are ‘making the best of a bad job’. Floater status may be imposed by limitations in the availability of mates or breeding space resulting in skewed population sex ratios, polygamous mating systems, high population densities and increased demand for specific breeding requirements such as space in colonies or adequate nesting cavities. Predictions concerning the effects of these factors have not been conducted to date. Few studies have been able to clarify the duration of floater status in any population. For short-lived species, floater status in a single breeding season may in fact imply zero lifetime reproductive success. In males, the existence of a considerable fraction of floaters attempting to breed may select for intense territorial behaviour and competitive mate guarding tactics in territory holders and in aggressive extrapair copulation and territory acquisition tactics in floaters. Interference competition from floaters may lead to density-dependent declines in reproductive success. In females, the attempts by floaters to attain breeding opportunities may have contributed to the observed propensities for female prospecting and for female-female aggression and the signalling of female dominance towards other females. Moreover, there may exist selection in females for signalling quality to mates in order to avoid being evicted by rivals. Excluding floaters from the analysis of sexually selected traits may severely affect sexual selection estimates because of biased sampling for large or more intensely expressed ornamentation. The importance of sexual selection may be negated or underestimated when in fact its action on floaters could be maintaining current levels of expression in the territorial fraction. Existing phenotypes should express, in their morphology, physiology and behaviour, the relentless drive through evolutionary time to avoid becoming a floater.

Differential Waterbird Population Dynamics After Long-Term Protection: The Influence of Diet and Habitat Type 
Alejandro Martínez-Abraín, Juan Jiménez, Juan Antonio Gómez and Daniel Oro

Using as a model system a long-term data set (1984–2014) of waterbird counts at nine large wetlands of Eastern Spain (Comunidad Valenciana), we explored the ecological drivers of population fluctuations, both during the wintering (34 species) and breeding (36 species) seasons. Most species showed increasing trends (80% during breeding, 62% in winter), including both initially common and rare species, suggesting a positive effect of site protection policies that were mainly applied in the 1980s. Specialised freshwater species such as diving ducks and coots did not show population recovery, most probably due to the characteristic tendency of shallow lagoons to remain eutrophic even after several decades of the implementation of sewage management and water purification. In fact re-introduction of a diet-specialist (red-knobbed coot) failed but that of a diet-generalist (purple swamphen) succeeded. Waterfowl hunting and the abandonment of rural practices also probably played a role in the lack of recovery by some species. Population trends of breeding species were more dependent on local conditions than trends of wintering populations. Body size could also have some influence on growth rates because some of the smallest species of shorebirds and Laridae (such as Kentish plovers, little terns and black-headed gulls) showed decreasing trends in one or both seasons. Finally, a few species were gained for the system as new wintering species, probably due to climate warming. Our results suggest that growth rates alone are poor descriptors of population fluctuations, especially for birds and other vagile taxa, and that it is more appropriate to interpret trends when considering natural regions spatially, and when growth rates are analysed within the time scale of the theoretical logistic curve.

Individual-Based Tracking Systems in Ornithology: Welcome to the Era of Big Data 
Pascual López-López

Technological innovations have led to exciting fast-moving developments in science. Today, we are living in a technology-driven era of biological discovery. Consequently, tracking technologies have facilitated dramatic advances in the fundamental understanding of ecology and animal behaviour. Major technological improvements, such as the development of GPS dataloggers, geolocators and other bio-logging technologies, provide a volume of data that were hitherto unconceivable. Hence we can claim that ornithology has entered the era of big data. In this paper, which is particularly addressed to undergraduate students and starting researchers in the emerging field of movement ecology, I summarise the current state of the art of individual-based tracking methods for birds as well as the most important challenges that, as a personal user, I consider we should address in future. To this end, I first provide a brief overview of individual tracking systems for birds. I then discuss current challenges for tracking birds with remote telemetry, including technological challenges (i.e., tag miniaturisation, incorporation of more bio-logging sensors, better efficiency in data archiving and data processing), as well as scientific challenges (i.e., development of new computational tools, investigation of spatial and temporal autocorrelation of data, improvement in environmental data annotation processes, the need for novel behavioural segmentation algorithms, the change from two to three, and even four, dimensions in the scale of analysis, and the inclusion of animal interactions). I also highlight future prospects of this research field including a set of scientific questions that have been answered by means of telemetry technologies or are expected to be answered in the future. Finally, I discuss some ethical aspects of bird tracking, putting special emphases on getting the most out of data and enhancing a culture of multidisciplinary collaboration among research groups.

Prioritising Research in Steppe Bird Conservation: A Literature Survey 
Manuel B. Morales and Juan Traba

With the aim to identify priorities in conservation-oriented research, this paper reviews the level of scientific attention given to steppe birds in Spain during the last 50 years. We surveyed scientific literature using Thomson Reuters Web of Science and the journal Ardeola, using the English names of 28 species of steppe birds and the word “Spain” as search terms. Every species was assigned a Scientific Attention Index (SAI), based on the number of articles published on each of them. In addition, a vulnerability measure (Vulnerability Score; VS) was calculated for each species on the basis of the trend estimate provided by the Sacre or Noctua monitoring programmes, or according to expert criteria. The sample gathered (432 articles) was a significant and thus representative proportion of WOS and Ardeola contents on the species considered. The most studied species was the red-legged partridge Alectoris rufa, with 83 papers (20.15%); while the least studied was the short-eared owl Asio flammeus (1 paper; 0.24%). The most studied knowledge area was Habitat Selection (92 papers; 22.17%), while the least was Niche/Climate, with nine papers (2.17%). Preferred habitat (grass steppe, shrub steppe or mixed) was not a significant factor in the level of scientific attention given to the different species. However, large-sized species (non-Passerines) were significantly more studied than small-sized ones (Passerines), indicating a research bias for the former group. Finally, no significant relationship was found between SAI and VS, which suggests that research effort has been allocated irrespective of the species' conservation status. These results highlight the scarce scientific attention given to most steppe birds in Spain in spite of their overall high vulnerability, and for most of the knowledge areas considered. On the other hand, they also show the high relative importance of research carried out in Spain, in both the Mediterranean and world contexts. This work underscores the need to focus scientific effort on certain species, especially those that currently show more regressive trends or higher levels of vulnerability, and in most areas of knowledge.

Birds in Ecological Networks: Insights from Bird-Plant Mutualistic Interactions 
Daniel García

Research in ecological networks has developed impressively in recent years. A significant part of this growth has been achieved using networks to represent the complexity of mutualistic interactions between species of birds and plants, such as pollination and seed dispersal. Bird-plant networks are built from matrices whose cells account for the field-sampled magnitudes of interaction (e.g. the number of plant fruits consumed by birds) in bird-plant species pairs. The comparative study of mutualistic networks evidences three general patterns in network structure: they are highly heterogeneous (many species having just a few interactions, but a few species being highly connected), nested (with specialists interacting with subsets of species with which generalists interact) and composed of weak and asymmetric relationships between birds and plants. This type of structure emerges from a set of ecological and evolutionary mechanisms accounting for the probabilistic role of species abundances and the deterministic role of species traits, often constrained by species phylogenies. Although bearing structural generalities, bird-plant networks are variable in space and time at very different scales: from habitat to latitudinal and biogeographical gradients, and from seasonal to inter-annual contrasts. They are also highly sensitive to human impact, being especially affected by habitat loss and fragmentation, defaunation and biological invasions. Further research on bird-plant mutualistic networks should: 1) apply wide conceptual frameworks which integrate the mechanisms of interaction and the responses of species to environmental gradients, 2) enlarge the ecological scale of networks across interaction types and animal groups, and 3) account for the ultimate functional (i.e. demographic) effects of trophic interactions.

Roles of Raptors in a Changing World: From Flagships to Providers of Key Ecosystem Services 
José A. Donázar, Ainara Cortés-Avizanda, Juan A. Fargallo, Antoni Margalida, Marcos Moleón, Zebensui Morales-Reyes, Rubén Moreno-Opo, Juan M. Pérez-García, José A. Sánchez-Zapata, Iñigo Zuberogoitia and David Serrano

Birds of prey have been, in comparison to other avian groups, an uncommon study model, mainly due to the limitations imposed by their conservative life strategy (low population density and turnover). Nonetheless, they have attracted a strong interest from the point of view of conservation biology because many populations have been close to extinction and because of their recognised role in ecosystems as top predators and scavengers and as flagship species. Today, after more than a century of persecution, and with the exception of some vultures still very much affected by illegal poisoning, many populations of birds of prey have experienced significant recoveries in many regions of Spain and the European Mediterranean. These changes pose new challenges when addressing the conservation of raptors in the coming decades. On this basis, and from a preferentially Mediterranean perspective, we have focused our attention on the need of describing and quantifying the role of these birds as providers of both regulating (rodent pest control and removal of livestock carcasses) and cultural ecosystem services. Moreover, we revisited persisting conflicts with human interests (predation of game species) and call attention to the emergence of new conflicts with a strong social and media component such as the predation on live cattle by vultures. Also, the rampant humanization of the environment determines the need for new solutions to the growing, yet scarcely explored, problem of accidents in new infrastructures such as mortality in wind farms. Finally, we explored in depth the ecological response of birds of prey to large-scale habitat changes such as urbanisation and abandonment of marginal lands that are also expected to increase in the near future. We urgently need more scientific knowledge to provide adequate responses to the challenge of keeping healthy populations of avian predators and scavengers in a rapidly changing world.