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Tuesday, 31 May 2016

Journal of Raptor Research. June 2016; Volume 50, Issue 2

Journal of Raptor Research
Published by: The Raptor Research Foundation


Table of Contents
Jun 2016 : Volume , 50 Issue 2

Mass Growth Rates, Plumage Development, and Related Behaviors of Snowy Owl (Bubo scandiacus) Nestlings Full Access
Denver W. Holt, Kathy Gray, Michael T. Maples and Mark A. Korte
In 1993 and 1995, we detailed body mass growth rates, plumage development, and related behaviors of Snowy Owl (Bubo scandiacus) nestlings from Barrow, Alaska. We recorded data from 71 of 80 nestlings from 14 of 20 nests in 1993 and 154 of 161 nestlings from 33 of 54 nests in 1995. Only nestlings for which we had data from hatching to at least 25 d of age were included in the growth model. Nestlings hatched between 1–3 d after “pipping” (creating a hole in) the eggshell. The semi-altricial young were covered in white protoptile (first) down plumage at hatching and weighed about 44–45 g. For about the first 7 d, their eyes were closed and movement was limited; the nestlings were dependent on the female for thermoregulation, food, and protection. Growth was rapid and by 8–9 d, the dark gray mesoptile (second) down had begun replacing protoptile down. By about 9–11 d, eyes were open, and by about 14 d, the owls were dark gray in color, and primary flight feather quills emerged. Mass gains were greatest the week prior to pre-fledging nest departure. The owls gained about 56 g every d, between 16–22 d. Around 21 d, the primary flight feathers erupted from their quills, and at approximately 25 d, tail (rectrices) feather quills erupted. After pre-fledging nest departure at approximately 21 d, the young owls roamed the tundra on foot and were fed and protected by both parents. We did not observe voluntary brood reduction; however, some young died in nests. Mass growth slowed substantially by about 34 d, while plumage development, particularly flight feather growth, increased rapidly. Young within and between nests, and years, grew at similar rates. Around 36–43 d, the young began their first attempts at flying, by hopping and pumping their wings. Also at this age, differences in plumage between presumed males and females were noticeable. Between 44 and 55 d, the young fledged, coinciding with the time when primary flight feather P8 reached 16.5 cm, and tail feather T1 reached 11.0 cm.
Dispersal and Survival of Juvenile Golden Eagles (Aquila chrysaetos) from Finnmark, Northern Norway Full Access
Torgeir Nygård, Karl-Otto Jacobsen, Trond Vidar Johnsen and Geir Helge Systad
The Golden Eagle (Aquila chrysaetos) in Fennoscandia has a widespread breeding range. In Norway, it spans from 58° in the south to 71° north in Finnmark County, making it likely the northernmost breeding population of this species in the world. To gain knowledge about their dispersal and movement behavior, we tagged 25 nestling Golden Eagles in Finnmark with satellite transmitters at the age of 7–11 wk during 2002–2011. About half of the birds made preliminary dispersals of more than 10 km from the nest, before dispersing permanently. The median date of permanent dispersal was 21 October. The main dispersal direction was southerly into the forested and agricultural areas in Sweden, but some birds also moved to Finland, Russia, and the Norwegian coast. The maximum dispersal distance from the natal area was ca. 1500 km. There was a return movement in the spring, with movement rates of about 20–30 km/day. The pattern of southerly migration in the autumn and northerly return in the spring was repeated over consecutive years. The overall survival rate was estimated at 58% during the first year of life, and 50% were alive after 2 yr. However, the birds that were hatched in the interior had higher survival rates than those hatched on the northernmost outer islands, and they also dispersed earlier than those from the coast. Illegal killing of Golden Eagles in northern Sweden was cause of mortality.
Using Banding and Encounter Data to Investigate Movements of Red-Tailed Hawks in the Northeastern United States Full Access
Joan L. Morrison and Jason M. Baird
We examined encounter records from 1925 to 2015 for Red-tailed Hawks banded in the northeastern U.S.A. (n = 1002) and characterized movement patterns by evaluating straight-line distances, difference in latitude, and directionality between banding and encounter locations. We define “encounter” as any handling of a live banded bird, any recovery (a banded bird found dead), and any resighting (reading and reporting a band number on a live bird without actually handling the bird). The mean direction of all hawk encounters was to the southwest of banding locations but some hawks ranged widely; encounters occurred in 27 states, including some in the Mississippi flyway, and in four Canadian provinces. Hawks banded as nestlings or as hatch-year birds (younger) were encountered at farther distances and across a wider range of latitudes than hawks banded as after-hatch-year (AHY) or after-second-year (ASY; older). Most encounters were of younger hawks. In mid-century, most known mortalities were due to shooting; more recent mortalities were due to collisions with vehicles, buildings, or other objects. Some young hawks apparently dispersed out of their natal areas or began migration by three mo post-fledging, and hawks hatched in the Northeast apparently do not migrate north during their first summer. Hawks banded at higher latitudes were encountered at locations farther south than hawks banded at lower latitudes, substantiating leapfrog migration in this species. Encounter data suggested philopatric tendencies; hawks banded as nestlings and encountered at >46 mo of age were encountered significantly closer to their natal areas than hawks banded as nestlings and encountered <46 mo after banding, and more than 10% of hawks banded as ASY or AHY were encountered after several years in the same 10-minute block in which they were banded. Hawks banded as nestlings and encountered at age >46 mo and >250 km from their natal area were considered long-distance dispersers. Between 1930 and 2010, for all hawks banded during the breeding season or summer and encountered in autumn or winter, the difference between banding latitude and encounter latitude decreased by about 4°, suggesting migratory short-stopping.
Breeding Biology of a Little-Known Raptor in Central China: The Chinese Sparrowhawk (Accipiter soloensis) Full Access
Qiang Ma, Lucia L. Severinghaus, Wen-Hong Deng and Zhengwang Zhang
The Chinese Sparrowhawk (Accipiter soloensis) is a little-known raptor distributed in southeast Asia. We here report a 5 yr study on its breeding biology at Dongzhai National Nature Reserve in Henan Province, central China. We banded 270 individuals (84 adults, 186 fledglings), recorded nest tree characteristics, and monitored nests with 24-hr digital cameras, video cameras, and ground observations from blinds. Among the 133 nests found, 91.7% were built on broad-leaved trees. Among 47 nests with known nest initiation dates, 57.4% were in mid-May. The most commonly used trees for nesting were chestnut (Castanea mollissima; 59.4%) and Chinese wingnut (Pterocarya stenoptera; 19.5%). Egg-laying occurred from 17 May to 17 June, with the largest number between 31 May and 4 June (n = 45, 28.9%). Eggs were laid throughout the day and also at night. Mean clutch size was 3.16 ± 0.75 eggs, with no significant interannual variation. Females contributed 87.4% of the total incubation effort. The incubation period was 28 ± 2 d (range 24–31 d, n = 46), and the nestlings fledged in 20.4 ± 1.6 d (range 18–25, n = 27). Overall breeding success was 58.7%, with no significant interannual variation. The daily nest survival rate was 0.993 ± 0.002 during incubation period, and 0.981 ± 0.003 during nestling period. Predation of eggs and nestlings by snakes and Eurasian Jays (Garrulus glandarius) was the main cause of nest failure.
Factors Influencing Burrowing Owl Abundance in Prairie Dog Colonies on the Southern High Plains of Texas Full Access
James D. Ray, Nancy E. McIntyre, Mark C. Wallace, Andrew P. Teaschner and Monty G. Schoenhals
Large numbers of Western Burrowing Owls (Athene cunicularia hypugaea) nest in black-tailed prairie dog (Cynomys ludovicianus) colonies in the southern high plains of Texas. Because the Western Burrowing Owl is a species of concern with an uncertain future due to widespread extirpation of prairie dogs, we examined the roles of prairie dog colony size, burrow density, proxies of prey availability, and vegetative composition and structure on owl abundance and reproductive rate. The number of nesting Burrowing Owl pairs was positively correlated to colony area (r2 = 0.550, P = 0.006) and to number of prairie dog burrows in a colony (r2 = 0.733, P = 0.0230). Burrowing Owl numbers and reproductive rate (maximum number of young seen per successful pair) were not related to our measures of vegetative composition and structure in prairie dog colonies, nor to indices of prey availability.
Great Gray Owls Nesting in Atypical, Low-Elevation Habitat in the Sierra Nevada, California Full Access
Julia S. Polasik, Joanna X. Wu, Kevin N. Roberts and Rodney B. Siegel
Great Gray Owls (Strix nebulosa) in the Sierra Nevada were once believed to nest strictly within mid-elevation conifer forests in close proximity to montane meadows. However, recent observations of Great Gray Owls nesting at lower elevations suggest the lower-montane zone of the Sierra Nevada, where oak-dominated woodlands transition to conifer-dominated forests, may also provide habitat for this California-listed endangered species. We describe the reproductive success, apparent occupancy rate, and habitat associated with eight Great Gray Owl nests monitored between 2006–2014 on commercial timberlands in the lower-montane zone of the central Sierra Nevada, California. Reproductive success was high, with several breeding attempts producing three fledglings, and an average of 1.9  ±  0.9 young fledged during 21 breeding attempts. Apparent occupancy rates were also high (87.5%  ±  20.9%) in the years following the discovery of a territory. Nests were in large-diameter (x¯ = 102.5 cm) trees, but smaller-diameter (25.4–50.7 cm) trees dominated the surrounding landscape, which was composed primarily of dense mixed conifer and hardwood forest interspersed with annual grasslands. Our results suggest that the lower-montane zone of the Sierra Nevada, though at the geographic limit of Great Gray Owl’s elevational range, can provide suitable nesting habitat. We used Maxent to identify potential Great Gray Owl nesting habitat throughout the lower-montane zone of the Sierra Nevada based on conditions around the nests we studied. Our model identified areas within 10 counties of the central and northern Sierra Nevada that we recommend be surveyed for Great Gray Owls. Identifying such locations could focus survey efforts to determine if this cryptic species is nesting in the identified areas, perhaps in numbers that may be a significant component of the very small statewide population.

Friday, 27 May 2016

The Condor. May 2016: Volume 118, Issue 2

The Condor
Published by: Cooper Ornithological Society

Table of Contents
May 2016 : Volume , 118 Issue 2
Scatter-hoarding corvids as seed dispersers for oaks and pines: A review of a widely distributed mutualism and its utility to habitat restoration
Mario B. Pesendorfer, T. Scott Sillett, Walter D. Koenig and Scott A. Morrison
Seed dispersal mutualisms with scatter-hoarders play a crucial role in population dynamics of temperate large-seeded trees. These behaviors shape seed dispersal patterns, which can be applied to conservation of populations, communities, and even ecosystems dominated by large-seeded trees. We draw on a growing body of literature to describe the ecological context and consequences of scatter-hoarding as a seed dispersal mechanism. We synthesize the quantitative literature on the interaction between members of the avian family Corvidae (crows, ravens, jays, magpies, and nutcrackers) and nut-bearing trees such as pines (Pinus spp.) and oaks (Quercus spp.) to examine unique aspects of avian scatter-hoarders as seed dispersers. During the scatter-hoarding process, seed selectivity, transportation distance, hoarding frequency, and cache placement affect seed dispersal effectiveness, a measure of the quantity and quality of dispersal. Case studies from around the world highlight the role of corvid seed dispersal in population dynamics of trees, and how the birds' scatter-hoarding behavior can be facilitated for the restoration of oak- and pine-dominated habitats. This mutualism, which provides many plant species with long-distance, high-quality seed dispersal, will likely become even more important for conservation of oak and pine ecosystems as suitable climates shift rapidly in the decades ahead. This ecosystem service provided by corvids could therefore serve as an efficient conservation tool.
The influence of agricultural transformation on the breeding performance of a top predator: Verreaux's Eagles in contrasting land use areas
Megan Murgatroyd, Les G. Underhill, Lucia Rodrigues and Arjun Amar
pg(s) 238–252
Breeding productivity frequently shows variation across a species' range or locally between different habitat types. Agricultural transformation generally has negative effects on biodiversity and often results in reduced prey abundance or increased foraging effort in top predators and, consequently, often reduces breeding productivity. Major factors that affect reproductive success also include climatic variables, breeding density, and timing of breeding. We explored the influence of agricultural transformation on a specialist raptor, Verreaux's Eagle (Aquila verreauxii). From 2011 to 2014, we examined productivity in 2 adjacent populations in the Western Cape Province, South Africa: an unspoiled area of Fynbos vegetation with little human development (the Cederberg Mountains) and an agriculturally transformed area (the Sandveld region). Counterintuitively, breeding productivity was higher in the agricultural than in the natural site. In particular, the proportion of pairs that attempted to breed (i.e. breeding rate) was higher in the Sandveld (0.94 ± 0.07 attempts pair−1 yr−1) than in the Cederberg (0.48 ± 0.14 attempts pair−1 yr−1). Nesting success was also higher in the Sandveld (0.80 ± 0.05 fledged young attempt−1 yr−1) than in the Cederberg (0.57 ± 0.13 fledged young attempt−1 yr−1), and the probability of nesting successfully was related to the lay date (decreased success with later laying) and to the total cumulative rainfall up to 28 days after hatching (decreased success with increasing rainfall). Using the site-specific breeding rates to produce a population model, we found that in isolation, the Cederberg population is unlikely to be self-sustaining, but Verreaux's Eagles breeding in the agriculturally developed Sandveld region are likely to be an important source population, despite occurring at a much lower density. These results, contrary to our expectations, suggest that Verreaux's Eagle may be more adaptable to agricultural transformation than previously thought, with breeding performance in the agricultural site adequate to maintain the population.
Black Curassow habitat relationships in terra firme forests of the Guiana Shield: A multiscale approach Full Access
Thomas Denis, Bruno Hérault, Gaëlle Jaouen, Olivier Brunaux, Stéphane Guitet and Cécile Richard-Hansen
The Black Curassow (Crax alector) is a large game bird with Vulnerable conservation status found in north-central South America. We examined its distributional pattern across French Guiana using a large number of environmental descriptors at 3 scales of analysis: landscape, forest type, and microhabitat. We used a hierarchical model with temporary emigration and imperfect detection for data collected by standard distance sampling methods at 35 study sites. At the landscape scale, Black Curassow density decreased with hunting pressure and increased with steeper slopes in both hunted and unhunted areas. Topography appeared to be a good proxy for Black Curassow ecological requirements and probably reflected habitat quality. At the forest scale, population density was negatively correlated with the abundance of palms and Mimosoideae and positively correlated with the abundance of Lauraceae. Botanical families did not directly influence Black Curassow distribution, but rather determined spatial patterns by being markers of a particular forest type. At the microhabitat scale, Black Curassows used hilltops more frequently than other parts of the local topographical gradient. Our multiscale analysis shows that this species' distribution can be explained by biotic or abiotic conditions, regardless of the scale. For conservation, we recommend maintaining connectivity between Black Curassow populations separated by hunted areas. Our predicted densities could be used to adapt hunting quotas across French Guiana's forests. We show that combining field and remote sensing data helps to understand the ecological processes responsible for Black Curassow habitat relationships.
Population estimates for tidal marsh birds of high conservation concern in the northeastern USA from a design-based survey Full Access
Whitney A. Wiest, Maureen D. Correll, Brian J. Olsen, Chris S. Elphick, Thomas P. Hodgman, David R. Curson and W. Gregory Shriver
Tidal marsh loss to anthropogenic environmental impacts and climate change, particularly sea level rise, has and will continue to cause declines in tidal marsh bird populations. Distribution patterns of tidal marsh birds are generally known, yet we lack detailed knowledge of local abundance and regional population sizes, which limits our ability to develop effective conservation strategies that will mitigate the impacts of marsh loss. We designed and implemented a probabilistic sampling framework to establish a regional marsh bird monitoring program, and collected baseline information for breeding tidal marsh birds in the northeastern USA (Maine to Virginia). We sampled 1,780 locations in 2011–2012 to provide regional population estimates for 5 tidal marsh–specialist birds. We estimated that there were 151,000 Clapper Rails (Rallus crepitans; 95% CI = 90,000–212,000), 117,000 Willets (Tringa semipalmata; 95% CI = 88,000–146,000), 5,000 Nelson's Sparrows (Ammodramus nelsoni; 95% CI = 1,000–9,000), 53,000 Saltmarsh Sparrows (A. caudacutus; 95% CI = 37,000–69,000), and 230,000 Seaside Sparrows (A. maritimus; 95% CI = 174,000–286,000) in northeastern tidal marshes. Our baseline assessment can be used to identify local habitat patches important to regional populations for each species and to prioritize conservation actions in targeted areas to maximize tidal marsh bird persistence. The flexibility and probabilistic design of our sampling framework also allow for integration with other monitoring programs (e.g., the U.S. Fish and Wildlife Service Salt Marsh Integrity Program and National Park Service Vital Signs Monitoring Program) so that inferences for these species can be made at multiple spatial scales.
Available data support protection of the Southwestern Willow Flycatcher under the Endangered Species Act Full Access
Tad C. Theimer, Aaron D. Smith, Sean M. Mahoney and Kirsten E. Ironside
Zink (2015) argued there was no evidence for genetic, morphological, or ecological differentiation between the federally endangered Southwestern Willow Flycatcher (Empidonax traillii extimus) and other Willow Flycatcher subspecies. Using the same data, we show there is a step-cline in both the frequency of a mtDNA haplotype and in plumage variation roughly concordant with the currently recognized boundary between E. t. extimus and E. t adastus, the subspecies with which it shares the longest common boundary. The geographical pattern of plumage variation is also concordant with previous song analyses differentiating those 2 subspecies and identified birds in one low-latitude, high-elevation site in Arizona as the northern subspecies. We also demonstrate that the ecological niche modeling approach used by Zink yields the same result whether applied to the 2 flycatcher subspecies or to 2 unrelated species, E. t. extimus and Yellow Warbler (Setophaga petechia). As a result, any interpretation of those results as evidence for lack of ecological niche differentiation among Willow Flycatcher subspecies would also indicate no differentiation among recognized species and would therefore be an inappropriate standard for delineating subspecies. We agree that many analytical techniques now available to examine genetic, morphological, and ecological differentiation would improve our understanding of the distinctness (or lack thereof) of Willow Flycatcher subspecies, but we argue that currently available evidence supports protection of the Southwestern Willow Flycatcher under the Endangered Species Act.
Sustainability assessment of Plain Pigeons and White-crowned Pigeons illegally hunted in Puerto Rico Full Access
Frank F. Rivera-Milán, G. Scott Boomer and Alexis J. Martínez
The Puerto Rican Plain Pigeon (Patagioenas inornata wetmorei) and the White-crowned Pigeon (P. leucocephala) are hunted illegally in Puerto Rico, despite being protected. Data are lacking to estimate how many are hunted illegally each year. For this reason, we used abundance estimates derived from distance sampling surveys conducted in 1986–2014 to (1) fit a Bayesian state-space model, (2) estimate posterior distributions for population and harvest management parameters (e.g., growth rate, carrying capacity, and maximum sustainable harvest rate), and (3) predict abundance in 2025 as a function of potential illegal hunting in 2015–2024. For the Plain Pigeon and White-crowned Pigeon, respectively, the intrinsic rate of population growth was 0.351 (95% credible interval = 0.086–0.737) and 0.352 (0.094–0.699), population carrying capacity was 55,840 (29,649–96,505) and 73,692 (47,225–98,434) individuals, maximum sustainable harvest rate was 0.176 (0.043–0.369 and 0.047–0.349), and predicted abundance was 20,536 (8,167–89,040) and 29,361 (1,779–100,937) individuals in 2025. Both pigeon populations increased from low numbers in the 1980–1990s, recovered quickly after hurricanes in 1989 and 1998, surpassed carrying capacity in 1995–2008, and decreased sharply at the same time that legal hunting of columbids increased in 2008–2014. Our monitoring and modeling results suggest that an increase in illegal hunting may be responsible for some of the abundance decline in 2008–2014, and that population sustainability may be affected by illegal hunting in 2015–2025. Therefore, data collection and the control of illegal hunting should be considered management priorities. Because we are updating model-based abundance predictions annually with monitoring data, we can inform management decisions, evaluate the results of conservation actions taken to maintain the pigeon populations fluctuating around carrying-capacity levels, and learn from the comparison of estimated and predicted abundances. Our monitoring and modeling scheme is applicable to other resident and migratory bird populations in the Caribbean.
Prey availability and habitat structure explain breeding space use of a migratory songbird Full Access
Vitek Jirinec, Robert E. Isdell and Matthias Leu
Researchers have long recognized that the spatial distribution of animals relates to habitat requirements. In birds, despite recent advances in tracking techniques, knowledge of habitat needs remains incomplete for most species. Using radio telemetry, we quantified the relative space use of 37 Wood Thrush (Hylocichla mustelina) males, captured over 2 years (2013, 2014) on their breeding grounds in coastal Virginia. Following tracking, we collected data on prey availability (n = 370 plots) and habitat structure (n = 222 plots) within bird home ranges, and modeled bird utilization distribution with both sets of variables using mixed models. Our objectives were to (a) determine the relative importance of habitat structure and prey availability for bird use, (b) identify specific resources that related to bird utilization distribution, (c) test the hypothesis that soil moisture explained prey availability, and (d) evaluate models by determining whether model-identified conditions agreed with data at sites where Wood Thrushes were absent over the preceding 5 years. Of prey variables, high-use areas within bird home ranges were linked to higher biomass of spiders and worm-like invertebrates, which were strongly correlated with soil moisture. Of habitat structure variables, bird use related negatively to red oak (Quercus spp.) count and pine (Pinus spp.) basal area, and positively to forest canopy height, snag basal area, and number and species richness of trees, among others. Evaluation of 12 covariates in our best model revealed that 5 were significant, with conditions at bird absence sites congruent with our models. Goodness-of-fit tests revealed poor fit of the prey-only model, whereas the habitat-only model explained nearly 8 times the variation in bird use. The model utilizing both prey and structure covariates yielded only marginal improvement over the habitat-only model. Consequently, management objectives aimed at habitat improvement for the declining Wood Thrush should particularly consider habitat structure resources.
A comparison of point-count and area-search surveys for monitoring site occupancy of the Coastal California Gnatcatcher (Polioptila californica californica) Full Access
William B. Miller and Clark S. Winchell
Improving the efficiency of monitoring protocols prescribed by conservation plans can release typically limited funding for other management and conservation activities. We present an approach for optimizing protocols that considers the precision of parameter estimates, costs of implementation, and broader monitoring-program goals. In a case study of the Coastal California Gnatcatcher (Polioptila californica californica), we compared the efficiency of point-count surveys (with and without playbacks of vocalizations) and area-search surveys (with playbacks) for estimating site occupancy. Conducting an area-search survey of a 2.25 ha plot required an average of 19 min longer than conducting an 18-min point-count survey (15 min of silent observation followed by 3 min of playbacks) at the same location. However, the estimated detection probability (p) during a single visit was lower for point counts (0.41 ± 0.05) than for area searches (0.69 ± 0.05), while both methods generated similar occupancy (Ψ) estimates (0.34 ± 0.06). To obtain the specified level of precision for estimates of occupancy (i.e. with 10% coefficient of variation), the total survey effort (travel time + survey time) was projected to be 35% lower for area searches than for point counts because of differences in detection probability and, thus, in the required numbers of sites and visits per site. For point counts, detection probability increased from 0.35 ± 0.02 to 0.46 ± 0.03 visit−1 after playbacks were broadcast at the end of the count. Free use of playbacks is one of the factors that contributed to the higher detection probability of the area-search method, but playbacks may introduce a slight positive bias into occupancy estimates. Because there are tradeoffs in switching to area-search methods, the decision to switch protocols demands full consideration of monitoring-program goals and the costs and benefits of each survey approach.
Anthropogenic light is associated with increased vocal activity by nocturnally migrating birds Full Access
Matthew J. Watson, David R. Wilson and Daniel J. Mennill
Anthropogenic modifications to the natural environment have profound effects on wild animals, through structural changes to natural ecosystems as well as anthropogenic disturbances such as light and noise. For animals that migrate nocturnally, anthropogenic light can interfere with migration routes, flight altitudes, and social activities that accompany migration, such as acoustic communication. We investigated the effect of anthropogenic light on nocturnal migration of birds through the Great Lakes ecosystem. Specifically, we recorded the vocal activity of migrating birds and compared the number of nocturnal flight calls produced above rural areas with ground-level artificial lights compared to nearby areas without lights. We show that more nocturnal flight calls are detected over artificially lit areas. The median number of nocturnal flight calls recorded at sites with artificial lights (31 per night, interquartile range: 15–135) was 3 times higher than at nearby sites without artificial lights (11 per night, interquartile range: 4–39). By contrast, the number of species detected at lit and unlit sites did not differ significantly (artificially lit sites: 6.5 per night, interquartile range: 5.0–8.8; unlit sites: 4.5 per night, interquartile range: 2.0–7.0). We conclude that artificial lighting changes the behavior of nocturnally migrating birds. The increased detections could be a result of ground-level light sources altering bird behavior during migration. For example, birds might have changed their migratory route to pass over lit areas, flown at lower altitudes over lit areas, increased their calling rate over lit areas, or remained longer over lit areas. Our results for ground-level lights correspond to previous findings demonstrating that migratory birds are influenced by lights on tall structures.
Shifting agriculture supports more tropical forest birds than oil palm or teak plantations in Mizoram, northeast India Full Access
Jaydev Mandal and T. R. Shankar Raman
Conversion of tropical forests and diverse multicrop agricultural land to commercial monocultures is a conservation concern worldwide. In northeast India, landscapes under shifting agriculture (or jhum) practiced by tribal communities are increasingly being replaced by monoculture plantations (e.g., teak, oil palm). We compared oil palm and teak plantations, shifting agricultural fields, and forest fallows (0–8 yr regeneration) with tropical rainforest edge and interior sites in Dampa Tiger Reserve, Mizoram, India. Twenty replicate transects were surveyed in each of the 5 study strata for vegetation structure, bird species richness and density, bird abundance, and species composition. Tree density and canopy and vertical structure were lowest in oil palm plantations, intermediate in teak plantations and jhum, and highest in rainforest sites. Tree density in jhum (4.3 stems per 100 m2) was much higher than in oil palm plantations (0.5 stems per 100 m2), but lower than in rainforest (6.8–8.2 stems per 100 m2), with bamboo absent in oil palm plantations and most abundant in regenerating jhum (25 culms per 50 m2). We recorded 107 bird species (94 forest species, 13 open-country species). Oil palm plantations had the lowest forest bird species richness (10 species), followed by teak plantations (38), while jhum (50) had only slightly lower species richness than the rainforest edge (58) and interior (70). Forest bird abundance in the jhum landscape was similar to that in rainforest, on average 304% higher than in oil palm plantations, and 87% higher than in teak plantations. Jhum sites were more similar in bird community composition to rainforest than were monocultures. Rapid recovery of dense and diverse secondary bamboo forests during fallow periods makes the shifting agricultural landscape mosaic a better form of land use for bird conservation than monocultures. Land use policy and conservation plans should provide greater support for shifting agriculture, while mandating better land use practices such as retention of forest remnants, native trees, and riparian vegetation in monoculture plantations.
Reproductive success of Horned Lark and McCown's Longspur in relation to wind energy infrastructure
Anika Mahoney and Anna D. Chalfoun
Wind energy is a rapidly expanding industry with potential indirect effects to wildlife populations that are largely unexplored. In 2011 and 2012, we monitored 211 nests of 2 grassland songbirds, Horned Lark (Eremophila alpestris) and McCown's Longspur (Rhynchophanes mccownii), at 3 wind farms and 2 undeveloped reference sites in Wyoming, USA. We evaluated several indices of reproductive investment and success: clutch size, size-adjusted nestling mass, daily nest survival rate, and number of fledglings. We compared reproductive success between wind farms and undeveloped sites and modeled reproductive success within wind farms as a function of wind energy infrastructure and habitat. Size-adjusted nestling mass of Horned Lark was weakly negatively related to turbine density. In 2011, nest survival of Horned Lark decreased 55% as turbine density increased from 10 to 39 within 2 km of the nest. In 2012, however, nest survival of Horned Lark was best predicted by the combination of vegetation height, distance to shrub edge, and turbine density, with survival increasing weakly with increasing vegetation height. McCown's Longspur nest survival was weakly positively related to vegetation density at the nest site when considered with the amount of grassland habitat in the neighborhood and turbine density within 1 km of the nest. Habitat and distance to infrastructure did not explain clutch size or number of fledglings for either species, or size-adjusted nestling mass for McCown's Longspur. Our results suggest that the influence of wind energy infrastructure varies temporally and by species, even among species using similar habitats. Turbine density was repeatedly the most informative measure of wind energy development. Turbine density could influence wildlife responses to wind energy production and may become increasingly important to consider as development continues in areas with high-quality wind resources.
Boreal bird abundance estimates within different energy sector disturbances vary with point count radius
Erin Bayne, Lionel Leston, C. Lisa Mahon, Péter Sólymos, Craig Machtans, Hedwig Lankau, Jeffrey R. Ball, Steven L. Van Wilgenburg, Steve G. Cumming, Trish Fontaine, Fiona K. A. Schmiegelow and Samantha J. Song
Responses of boreal birds to changes in forest structure and composition caused by construction of well pads, seismic lines, and pipelines are poorly understood. Bird species associated with older forests are predicted to experience larger population declines with increased disturbance compared with species associated with younger or open habitats; however, point count methods may influence apparent outcomes because the proportional area of disturbed vegetation and the magnitude, uncertainty, and detection of a disturbance response by birds vary as a function of sampling area. We analyzed point count data from 12 energy sector studies and measured how disturbance type and point count radius interacted to affect 531 impact ratios (mean abundance at point counts centered within disturbances relative to abundance at point counts within forest 150–400 m from the nearest edge bordering those disturbances [59 species*3 disturbance types*3 point count radii]). We observed larger disturbance effects (impact ratios) within larger-radius point counts at well pads (100-m and unlimited-distance) and pipelines (unlimited-distance) compared with 50-m point counts at seismic lines, and within 50-m point counts at well pads relative to 50-m point counts at seismic lines. Effect uncertainty was higher at well pads and pipelines than seismic lines, and lower within larger-radius point counts. The probability of detecting a disturbance response was greater for larger-radius point counts at pipelines than for 50-m point counts at seismic lines, and within 50-m point counts at well pads relative to 50-m point counts at seismic lines. On average, a species was more likely to increase in abundance near an energy sector disturbance if the species was not associated with older (>75 yr) forest stages. While the effects of disturbance varied by species and with disturbance type, the effects of pipelines and seismic lines were better detected by larger-radius point counts, while the effects of well pads were better detected by smaller-radius point counts.
Wintering Sandhill Crane exposure to wind energy development in the central and southern Great Plains, USA
Aaron T. Pearse, David A. Brandt and Gary L. Krapu
Numerous wind energy projects have been constructed in the central and southern Great Plains, USA, the main wintering area for midcontinental Sandhill Cranes (Grus canadensis). In an initial assessment of the potential risks of wind towers to cranes, we estimated spatial overlap, investigated potential avoidance behavior, and determined the habitat associations of cranes. We used data from cranes marked with platform transmitting terminals (PTTs) with and without global positioning system (GPS) capabilities. We estimated the wintering distributions of PTT-marked cranes prior to the construction of wind towers, which we compared with current tower locations. Based on this analysis, we found 7% spatial overlap between the distributions of cranes and towers. When we looked at individually marked cranes, we found that 52% would have occurred within 10 km of a tower at some point during winter. Using data from cranes marked after tower construction, we found a potential indication of avoidance behavior, whereby GPS-marked cranes generally used areas slightly more distant from existing wind towers than would be expected by chance. Results from a habitat selection model suggested that distances between crane locations and towers may have been driven more by habitat selection than by avoidance, as most wind towers were constructed in locations not often selected by wintering cranes. Our findings of modest regional overlap and that few towers have been placed in preferred crane habitat suggest that the current distribution of wind towers may be of low risk to the continued persistence of wintering midcontinental Sandhill Cranes in the central and southern Great Plains.
Collision avoidance by migrating raptors encountering a new electric power transmission line
Jeff Luzenski, Claudia E. Rocca, Richard E. Harness, John L. Cummings, Daryl D. Austin, Melissa A. Landon and James F. Dwyer
Avian collisions with overhead power lines are of conservation concern, particularly in migration corridors. We studied potential collisions where an existing power line supported by towers 20–25 m tall was replaced by the Susquehanna-Roseland line (S-R line), a new line with towers 55–60 m tall. The S-R line crosses Kittatinny Ridge, a corridor for raptors migrating south through New Jersey and Pennsylvania, USA. We hypothesized that the S-R line, which on Kittatinny Ridge includes markers designed to increase its visibility to birds, would cause migrating raptors to react in 1 of 3 ways: (1) to not alter flight elevation, but to pass safely through the S-R wire zone; (2) to not alter flight elevation, and to not pass safely through the wire zone, leading to collisions; or (3) to alter flight elevation and to pass safely above or below the S-R wire zone. To evaluate these hypotheses, we recorded the flight elevations of migrating raptors in 2013 before construction of the S-R line and in 2014 postconstruction. Preconstruction, we recorded 3,698 raptor crossings. Most raptors (72%) crossed above the anticipated S-R wire zone. Some (24%) passed through the anticipated S-R wire zone, and a few (4%) passed below the anticipated S-R wire zone. Postconstruction, we recorded 4,482 crossings. Most raptors (92%) crossed above the S-R wire zone. A few passed through (5%) or below (3%) the S-R wire zone. Postconstruction, raptors responded to the new line by flying higher than they had when traversing the previous line. We did not observe any collisions. Altered flight elevations and the absence of observed collisions supported hypothesis 3. If similar patterns occur at other lines that cross diurnal migration corridors along ridges, then future monitoring may be better focused on potentially riskier settings, such as areas where migrating birds do not have deflected winds to assist with gaining elevation.
Avian interactions with renewable energy infrastructure: An update
Jennifer A. Smith and James F. Dwyer
Energy infrastructure is widespread worldwide. Renewable energy technologies, which are expanding their footprint on the landscape and their contribution to energy availability, represent a different kind of infrastructure from extractive energy technologies. Although renewable energy sources may offer a ‘greener alternative' to traditional extractive energy sources, mounting evidence suggests that renewable energy infrastructure, and the transmission lines needed to convey energy from renewable energy facilities to users, may impact birds. Peer-reviewed literature historically has focused on the direct effects of electrocution and, to a lesser extent, collisions with overhead power systems, and on avian collisions at wind energy facilities, with less consideration of indirect effects or other energy sectors. Here, we review studies that have examined direct and indirect effects on birds at utility-scale onshore wind- and solar-energy facilities, including their associated transmission lines. Although both direct and indirect effects appear site-, species-, and infrastructure-specific, generalities across energy sectors are apparent. For example, large-bodied species with high wing loading and relatively low maneuverability appear to be especially susceptible to direct effects of tall structures, and the risk of collision is likely greater when structures are placed perpendicular to flight paths or in areas of high use. Given that all infrastructure types result in direct loss or fragmentation of habitat and may affect the distribution of predators, indirect effects mediated by these mechanisms may be pervasive across energy facilities. When considered together, the direct and indirect effects of renewable energy facilities, and the transmission lines serving these facilities, are likely cumulative. Ultimately, cross-facility and cross-taxon meta-analyses will be necessary to fully understand the cumulative impacts of energy infrastructure on birds. Siting these facilities in a way that minimizes avian impacts will require an expanded understanding of how birds perceive facilities and the mechanisms underlying direct and indirect effects.
Avian interactions with energy infrastructure in the context of other anthropogenic threats
Scott R. Loss
Continued global expansion in the development of energy and its associated infrastructure is expected in the coming decades. Substantial concern exists about the impacts of this energy infrastructure on bird populations. In this special section, Smith and Dwyer (2016) provide a timely review of interactions between birds and renewable energy infrastructure, and several studies address avian interactions with renewable and nonrenewable energy infrastructure. I briefly summarize these studies and place avian interactions with energy infrastructure in the context of the many anthropogenic threats to birds. There is vast variation in the amount of mortality caused by different man-made threats. Comparing threats in the context of energy development is useful for attracting public, scientific, and policy attention, for highlighting major research gaps, for providing scientific evidence to inform resource allocation decisions, and for developing mitigation strategies whereby mortality risk from one threat can be offset by reducing risk from another threat. However, broad comparisons of mortality should not be used on their own to draw conclusions about population-level impacts, to conclude that low mortality or a paucity of information negates biologically significant impacts or obviates a need for action, or to develop mortality mitigation strategies when little information exists to inform the balancing of risks. To move beyond gross mortality estimates toward comparisons of actual population-level impacts, a balance must be struck between conducting research that produces generalizable results and studies that focus on species, locations, and response variables of interest. Additional information about the many direct and indirect effects of energy infrastructure, such as the research described by the articles in this special section, will be crucial to achieving an optimal tradeoff between energy development and wildlife conservation.
Predation and reduced grazing interact to reduce recruitment and population growth in Black Brant Full Access
James S. Sedinger, Christopher A. Nicolai, Amanda W. VanDellen, Alan G. Leach, Heather M. Wilson and R. Michael Anthony
Dynamics of avian populations may be governed by a complex interaction between immediate effects of predation and longer-term trophic feedbacks between individuals and their foods. We used a long-term study of uniquely marked Black Brant geese (Branta bernicla nigricans) to estimate recruitment into the breeding population. We related recruitment to nest success, which directly affects recruitment 2 to 3 years later. We also assessed similarly time-lagged relationships between recruitment and number of nests in the colony, a measure of local density, and pre-fledging and first-year survival, the latter of which is strongly influenced by growth conditions and food availability for young of the year. We assessed relationships between number of recruits and explanatory variables in 2 sets of models, which either included or excluded a linear trend across years in numbers of recruits. The best-performing models in each model set explained a substantial proportion of the variation in numbers of recruits 2 to 3 years later (85 and 78% in the 2 model sets, respectively). First-year survival was an important predictor of number of recruits in both sets of models, whereas nest success was important only in models lacking a trend across years. Number of nests in the colony had a relatively weak negative association with number of recruits. First-year survival reflects a lagged response to earlier nest-predation events. Reduced grazing during predation events can result in loss of grazing lawns and thus reduced growth rates of future cohorts of goslings, which are regulated by food abundance and density of broods. Our finding that recruitment is insufficient to maintain the breeding population results from both direct effect of predation on nests, primarily by Arctic foxes (Alopex lagopus), and longer-term indirect effects of such predation on first-year survival of Black Brant.

Thursday, 26 May 2016

What's new for 'birdRS' in PubMed. May 2016, Week 3

birdRS - Latest Research News

PubMed Results
1.Molecular Ecological Insights into Neotropical Bird-Tick Interactions.
Miller MJ, Esser HJ, Loaiza JR, Herre EA, Aguilar C, Quintero D, Alvarez E, Bermingham E.
PLoS One. 2016 May 20;11(5):e0155989. doi: 10.1371/journal.pone.0155989. eCollection 2016.


In the tropics, ticks parasitize many classes of vertebrate hosts. However, because many tropical tick species are only identifiable in the adult stage, and these adults usually parasitize mammals, most attention on the ecology of tick-host interactions has focused on mammalian hosts. In contrast, immature Neotropical ticks are often found on wild birds, yet difficulties in identifying immatures hinder studies of birds' role in tropical tick ecology and tick-borne disease transmission. In Panama, we found immature ticks on 227 out of 3,498 individually-sampled birds representing 93 host species (24% of the bird species sampled, and 13% of the Panamanian land bird fauna). Tick parasitism rates did not vary with rainfall or temperature, but did vary significantly with several host ecological traits. Likewise, Neotropical-Nearctic migratory birds were significantly less likely to be infested than resident species. Using a molecular library developed from morphologically-identified adult ticks specifically for this study, we identified eleven tick species parasitizing birds, indicating that a substantial portion of the Panamanian avian species pool is parasitized by a diversity of tick species. Tick species that most commonly parasitized birds had the widest diversity of avian hosts, suggesting that immature tick species are opportunistic bird parasites. Although certain avian ecological traits are positively associated with parasitism, we found no evidence that individual tick species show specificity to particular avian host ecological traits. Finally, our data suggest that the four principal vectors of Rocky Mountain Spotted Fever in the Neotropics rarely, if ever, parasitize Panamanian birds. However, other tick species that harbor newly-discovered rickettsial parasites of unknown pathogenicity are frequently found on these birds. Given our discovery of broad interaction between Panamanian tick and avian biodiversity, future work on tick ecology and the dynamics of emerging tropical tick-borne pathogens should explicitly consider wild bird as hosts.

PMID: 27203693 [PubMed - as supplied by publisher]

2.Complete Genome Sequence of a Novel Avian Paramyxovirus (APMV-13) Isolated from a Wild Bird in Kazakhstan.
Karamendin K, Kydyrmanov A, Seidalina A, Asanova S, Sayatov M, Kasymbekov E, Khan E, Daulbayeva K, Harrison SM, Carr IM, Goodman SJ, Zhumatov K.
Genome Announc. 2016 May 19;4(3). pii: e00167-16. doi: 10.1128/genomeA.00167-16.


A novel avian paramyxovirus was identified during annual viral surveillance of wild bird populations in Kazakhstan in 2013. The virus was isolated from a white fronted goose (Anser albifrons) in northern Kazakhstan. Here, we report the complete genome sequence of the isolate, which we suggest should constitute a novel serotype.
PMID: 27198008 [PubMed]

3.Determinants of bird conservation action implementation and associated population trends of threatened species.
Luther DA, Brooks TM, Butchart SH, Hayward MW, Kester ME, Lamoreux J, Upgren A.
Conserv Biol. 2016 May 16. doi: 10.1111/cobi.12757. [Epub ahead of print]


Conservation actions, such as habitat protection, attempt to halt the loss of threatened species and help their populations to recover. Various research has examined the efficiency and the effectiveness of actions individually. However, conservation actions generally occur simultaneously so the full suite of implemented conservation actions should be assessed. We used the conservation actions underway for all threatened and near-threatened birds of the world (IUCN Red List of Threatened Species) to assess which biological (related to taxonomy and ecology) and anthropogenic (related to geo-economics) factors are associated with the implementation of different classes of conservation actions. We also assessed which conservation actions are associated with population increases in the species targeted. Extinction risk category was the strongest single predictor of the type of conservation actions implemented, followed by landmass type (continent, oceanic island, etc.) and generation length. Species targeted by invasive alien species control/eradication programs, ex situ conservation, international legislation, reintroduction, or education and awareness-raising activities were more likely to have increasing populations. These results illustrate the importance of developing a predictive science of conservation actions and the relative benefits of each class of implemented conservation action for threatened and near-threatened birds worldwide. This article is protected by copyright. All rights reserved.
PMID: 27197021 [PubMed - as supplied by publisher]

4.Rhythmic Continuous-Time Coding in the Songbird Analog of Vocal Motor Cortex.
Lynch GF, Okubo TS, Hanuschkin A, Hahnloser RH, Fee MS.
Neuron. 2016 May 18;90(4):877-92. doi: 10.1016/j.neuron.2016.04.021.


Songbirds learn and produce complex sequences of vocal gestures. Adult birdsong requires premotor nucleus HVC, in which projection neurons (PNs) burst sparsely at stereotyped times in the song. It has been hypothesized that PN bursts, as a population, form a continuous sequence, while a different model of HVC function proposes that both HVC PN and interneuron activity is tightly organized around motor gestures. Using a large dataset of PNs and interneurons recorded in singing birds, we test several predictions of these models. We find that PN bursts in adult birds are continuously and nearly uniformly distributed throughout song. However, we also find that PN and interneuron firing rates exhibit significant 10-Hz rhythmicity locked to song syllables, peaking prior to syllable onsets and suppressed prior to offsets-a pattern that predominates PN and interneuron activity in HVC during early stages of vocal learning.
PMID: 27196977 [PubMed - in process]

5.Continuous Time Representations of Song in Zebra Finches.
Troyer TW.
Neuron. 2016 May 18;90(4):672-4. doi: 10.1016/j.neuron.2016.05.013.


Neurons in the songbird nucleus HVC produce premotor bursts time locked to song with millisecond precision. In this issue of Neuron, Lynch et al. (2016) and Picardo et al. (2016) provide convincing evidence that the population of these bursts contain a continuous representation of time throughout song.
PMID: 27196971 [PubMed - in process]

Vaughan-Higgins R, Vitali S, Reiss A, Besier S, Hollingsworth T, Smith G.
J Wildl Dis. 2016 May 19. [Epub ahead of print]


Published avian reference ranges for plasma cholinesterase (ChE) and brain acetylcholinesterase (AChE) are numerous. However, a consistently reported recommendation is the need for species- and laboratory-specific reference ranges because of variables, including assay methods, sample storage conditions, season, and bird sex, age, and physiologic status. We developed normal reference ranges for brain AChE and plasma total ChE (tChE) activity for Carnaby's Black-Cockatoos (Calyptorhynchus latirostris) using a standardized protocol (substrate acetylthiocholine at 25 C). We report reference ranges for brain AChE (19-41 μmol/min per g, mean 21±6.38) and plasma tChE (0.41-0.53 μmol/min per mL, mean 0.47±0.11) (n=15). This information will be of use in the ongoing field investigation of a paresis-paralysis syndrome in the endangered Carnaby's Black-Cockatoos, suspected to be associated with exposure to anticholinesterase compounds and add to the paucity of reference ranges for plasma tChE and brain AChE in Australian psittacine birds.
PMID: 27195690 [PubMed - as supplied by publisher]

7.Impact of Management on Avian Communities in the Scottish Highlands.
Newey S, Mustin K, Bryce R, Fielding D, Redpath S, Bunnefeld N, Daniel B, Irvine RJ.
PLoS One. 2016 May 19;11(5):e0155473. doi: 10.1371/journal.pone.0155473. eCollection 2016.


The protection of biodiversity is a key national and international policy objective. While protected areas provide one approach, a major challenge lies in understanding how the conservation of biodiversity can be achieved in the context of multiple land management objectives in the wider countryside. Here we analyse metrics of bird diversity in the Scottish uplands in relation to land management types and explore how bird species composition varies in relation to land managed for grazing, hunting and conservation. Birds were surveyed on the heather moorland areas of 26 different landholdings in Scotland. The results indicate that, in relation to dominant management type, the composition of bird species varies but measures of diversity and species richness do not. Intensive management for grouse shooting affects the occurrence, absolute and relative abundance of bird species. While less intensive forms of land management appear to only affect the relative abundance of species, though extensive sheep grazing appears to have little effect on avian community composition. Therefore enhanced biodiversity at the landscape level is likely to be achieved by maintaining heterogeneity in land management among land management units. This result should be taken into account when developing policies that consider how to achieve enhanced biodiversity outside protected areas, in the context of other legitimate land-uses.
PMID: 27195486 [PubMed - in process] Free Article

8.Long-term climate impacts on breeding bird phenology in Pennsylvania, USA.
McDermott ME, DeGroote LW.
Glob Chang Biol. 2016 May 19. doi: 10.1111/gcb.13363. [Epub ahead of print]


Climate change is influencing bird phenology worldwide, but we still lack information on how many species are responding over long temporal periods. We assessed how climate affected passerine reproductive timing and productivity at a constant effort mist-netting station in western Pennsylvania using a model comparison approach. Several lines of evidence point to the sensitivity of 21 breeding passerines to climate change over five decades. The trends for temperature and precipitation over 53 years were slightly positive due to intraseasonal variation, with the greatest temperature increases and precipitation declines in early spring. Regardless of broodedness, migration distance, or breeding season, 13 species hatched young earlier over time with most advancing >3 days per decade. Warm springs were associated with earlier captures of juveniles for 14 species, ranging from 1-3 days advancement for every 1°C increase. This timing was less likely to be influenced by spring precipitation; nevertheless, higher rainfall was usually associated with later appearance of juveniles and breeding condition in females. Temperature and precipitation were positively related to productivity for seven and eleven species, respectively, with negative relations evident for six and eight species. We found that birds fledged young earlier with increasing spring temperatures, potentially benefiting some multi-brooded species. Indeed, some extended the duration of breeding in these warm years. Yet, a few species fledged fewer juveniles in warmer and wetter seasons, indicating that expected future increases could be detrimental to locally breeding populations. Although there were no clear relationships between life history traits and breeding phenology, species-specific responses to climate found in our study provide novel insights into phenological flexibility in songbirds. Our research underscores the value of long-term monitoring studies and the importance of continuing constant effort sampling in the face of climate change. This article is protected by copyright. All rights reserved.
PMID: 27195453 [PubMed - as supplied by publisher]

9.How to reduce the costs of ornaments without reducing their effectiveness? An example of a mechanism from carotenoid-based plumage.
Surmacki A, Ragan A, Kosiński Z, Tobółka M, Podkowa P.
Behav Ecol Sociobiol. 2016;70:695-700. Epub 2016 Feb 29.

Carotenoid-based ornaments are often considered to be honest indicators of individual quality assessed by potential mates. However, males can use a variety of strategies that minimize the amount of costly carotenoids used while retaining the effectiveness of color signaling. Birds could do this by altering pigment intake, metabolism, or its presentation to a potential signal receiver. Here, we propose a new mechanism of lowering the costs of carotenoid displays in birds: differential allocation of pigments within single feathers. We studied the coloration of the yellow terminal tail bands of rectrices of male Bohemian waxwings. Using reflectance spectrometry, we show that the two central rectrices are most intensively colored compared to other rectrices. More detailed analyses reveal that these differences result from feather-specific patterns of rectrices coloration. The outer feather vanes of the outermost rectrices are more intensively colored compared to the inner vanes. However, the central rectrices have equally colored vanes that are, on average, more intensively pigmented than the outermost rectrices. When the waxwing tail is folded, the outermost rectrices are covered by other feathers, except for the narrow, outer vane. Central rectrices, however, form the outermost layers which are not obscured by other tail feathers. Thus, the feather vanes that are the most visible to potential viewers are also the most pigmented. These results support the occurrence of a previously overlooked mechanism to reduce the costs of carotenoid-based ornaments: precise pigment distribution to maximize efficiency of signals within single feathers.

Males of many bird species use bright carotenoid-based plumage coloration to attract females. These traits are physiologically expensive such that only individuals in prime condition can develop the most vivid colors. Males often "cheat" to obtain attractive appearances at lower costs. We showed that this goal could be achieved by differential deposition of pigments into the most conspicuous feather regions. Bohemian waxwing males have yellow tips on their rectrices of which the outer vanes are more brightly colored compared to the inner vanes. These inner feather vanes are usually covered by other feathers and are, thus, less visible to conspecifics. The only exception is the pair of central rectrices that are fully exposed, and both feather vanes are equally colored. In this species, males minimize the use of costly carotenoid pigments while maintaining elaborate ornamentation of plumage regions that are most visible to potential mates.
PMID: 27194821 [PubMed]

10.Food supplementation mitigates dispersal-dependent differences in nest defence in a passerine bird.
Récapet C, Daniel G, Taroni J, Bize P, Doligez B.
Biol Lett. 2016 May;12(5). pii: 20160097. doi: 10.1098/rsbl.2016.0097.


Dispersing and non-dispersing individuals often differ in phenotypic traits (e.g. physiology, behaviour), but to what extent these differences are fixed or driven by external conditions remains elusive. We experimentally tested whether differences in nest-defence behaviour between dispersing and non-dispersing individuals changed with local habitat quality in collared flycatchers, by providing additional food during the nestling rearing period. In control (non-food-supplemented) nests, dispersers were less prone to defend their brood compared with non-dispersers, whereas in food-supplemented nests, dispersing and non-dispersing individuals showed equally strong nest defence. We discuss the importance of dispersal costs versus adaptive flexibility in reproductive investment in shaping these differences in nest-defence behaviour between dispersing and non-dispersing individuals. Irrespective of the underlying mechanisms, our study emphasizes the importance of accounting for environmental effects when comparing traits between dispersing and non-dispersing individuals, and in turn assessing the costs and benefits of dispersal.
PMID: 27194287 [PubMed - in process]

11.Bone-associated gene evolution and the origin of flight in birds.
Machado JP, Johnson WE, Gilbert MT, Zhang G, Jarvis ED, O'Brien SJ, Antunes A.
BMC Genomics. 2016 May 18;17(1):371. doi: 10.1186/s12864-016-2681-7.


Bones have been subjected to considerable selective pressure throughout vertebrate evolution, such as occurred during the adaptations associated with the development of powered flight. Powered flight evolved independently in two extant clades of vertebrates, birds and bats. While this trait provided advantages such as in aerial foraging habits, escape from predators or long-distance travels, it also imposed great challenges, namely in the bone structure.
We performed comparative genomic analyses of 89 bone-associated genes from 47 avian genomes (including 45 new), 39 mammalian, and 20 reptilian genomes, and demonstrate that birds, after correcting for multiple testing, have an almost two-fold increase in the number of bone-associated genes with evidence of positive selection (~52.8 %) compared with mammals (~30.3 %). Most of the positive-selected genes in birds are linked with bone regulation and remodeling and thirteen have been linked with functional pathways relevant to powered flight, including bone metabolism, bone fusion, muscle development and hyperglycemia levels. Genes encoding proteins involved in bone resorption, such as TPP1, had a high number of sites under Darwinian selection in birds.

Patterns of positive selection observed in bird ossification genes suggest that there was a period of intense selective pressure to improve flight efficiency that was closely linked with constraints on body size.
PMID: 27193938 [PubMed - in process] Free Article

12.Is Cerebellar Architecture Shaped by Sensory Ecology in the New Zealand Kiwi (Apteryx mantelli).
Corfield JR, Kolominsky J, Craciun I, Mulvany-Robbins BE, Wylie DR.
Brain Behav Evol. 2016 May 19. [Epub ahead of print]


Among some mammals and birds, the cerebellar architecture appears to be adapted to the animal's ecological niche, particularly their sensory ecology and behavior. This relationship is, however, not well understood. To explore this, we examined the expression of zebrin II (ZII) in the cerebellum of the kiwi (Apteryx mantelli), a fully nocturnal bird with auditory, tactile, and olfactory specializations and a reduced visual system. We predicted that the cerebellar architecture, particularly those regions receiving visual inputs and those that receive trigeminal afferents from their beak, would be modified in accordance with their unique way of life. The general stripe-and-transverse region architecture characteristic of birds is present in kiwi, with some differences. Folium IXcd was characterized by large ZII-positive stripes and all Purkinje cells in the flocculus were ZII positive, features that resemble those of small mammals and suggest a visual ecology unlike that of other birds. The central region in kiwi appeared reduced or modified, with folium IV containing ZII+/- stripes, unlike that of most birds, but similar to that of Chilean tinamous. It is possible that a reduced visual system has contributed to a small central region, although increased trigeminal input and flightlessness have undoubtedly played a role in shaping its architecture. Overall, like in mammals, the cerebellar architecture in kiwi and other birds may be substantially modified to serve a particular ecological niche, although we still require a larger comparative data set to fully understand this relationship.
PMID: 27192984 [PubMed - as supplied by publisher]

13.The influence of fire on the assemblage structure of foraging birds in grasslands of the Serra da Canastra National Park, Brazil.
Reis MG, Fieker CZ, Dias MM.
An Acad Bras Cienc. 2016 May 13. pii: S0001-37652016005006101. [Epub ahead of print]


Grasslands are the most threatened physiognomies of the Cerrado biome (Brazilian savanna), a biodiversity hotspot with conservation as a priority. The Serra da Canastra National Park protects the most important remnants of the Cerrado's southern grasslands, which are under strong anthropogenic pressure. The present study describes the structure of bird assemblages that directly use food resources in burned areas, comparing areas affected by natural fire to the areas where controlled fires were set (a management strategy to combat arson). The tested null hypothesis was that different bird assemblages are structured in a similar manner, regardless of the post-fire period or assessed area. Between December/2012 and January/2015, 92 species were recorded foraging in the study areas. The results indicate that both types of burnings triggered profound and immediate changes in bird assemblages, increasing the number of species and individuals. Natural fires exhibited a more significant influence on the structure (diversity and dominance) than prescribed burnings. Nevertheless, all the differences were no longer noticeable after a relatively short time interval of 2-3 months after prescribed burnings and 3-4 after natural fires. The findings may help the understanding of prescribed burnings as a management strategy for bird conservation in grasslands.
PMID: 27192195 [PubMed - as supplied by publisher] Free Article

14.Frugivory and seed dispersal of Solanum granuloso-leprosum Dunal (Solanaceae) by birds in deciduous seasonal forest.
Jacomassa FA.
Braz J Biol. 2016 May 17. pii: S1519-69842016005112113. [Epub ahead of print]


The goal of this study was to identify which bird species consume Solanum granuloso-leprosum fruits and disperse its seeds. 60 hours of focal observations were carried out between April and May 2006 on the edge of a deciduous forest fragment in the Uruguay River region, Rio Grande do Sul state, Brazil. Ten species were observed in total removing 443 fruits. Saltator similis removed 61.8% of the fruits, followed by Tangara sayaca (17.1%), Pipraeidea bonariensis (11.7%), and T. preciosa (6.8%), while the remaining six species accounted for only 2.5% of the fruits removed. Most fruit removal occurred early in the day or mid-afternoon. The most common feeding behaviors were picking (60.7%), followed by stalling (23%) and hovering (16%). Birds flew more than 10 m from the fruit plant in 62% of the removal events. All bird species observed here may be considered potential dispersers of S. granuloso-leprosum, as they moved the seeds away from the mother plant where strong competition and predation are likely to occur. Results also suggest that S. granuloso-leprosum may be useful in ecological restoration programs.
PMID: 27191463 [PubMed - as supplied by publisher] Free Article