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Thursday, 8 May 2014

The Condor (Journal), May 2014: Volume 116 Issue 2 - Contents and Abstracts

The Condor

Published by: Cooper Ornithological Society

Table of Contents

May 2014 : Volume 116 Issue 2 


Integrating aerial and ship surveys of marine birds into a combined density surface model: A case study of wintering Common Loons Full Access

Kristopher J. Winiarski, M. Louise Burt, Eric Rexstad, David L. Miller, Carol L. Trocki, Peter W. C. Paton, and Scott R. McWilliams
pg(s) 149–161


Biologists now use a variety of survey platforms to assess the spatial distribution and abundance of marine birds, yet few attempts have been made to integrate data from multiple survey platforms to improve model accuracy or precision. We used density surface models (DSMs) to incorporate data from two survey platforms to predict the distribution and abundance of a diving marine bird, the Common Loon (Gavia immer). We conducted strip transect surveys from a multiengine, fixed-wing aircraft and line surveys from a 28 m ship during winter 2009–2010 in a 3,800 km2 study area off the coast of Rhode Island, USA. We accounted for imperfect detection and availability bias due to Common Loon diving behavior. We incorporated spatially explicit environmental covariates (water depth and latitude) to provide predictions of the spatial distribution and abundance of wintering Common Loons. The combined-platform DSM estimated the highest Common Loon densities (>20 individuals km−2) in nearshore waters <35 m deep, with an average daily abundance of 5,538 (95% CI = 4,726–6,489) individuals in the study area. The combined-platform model offered substantial improvement in the precision of abundance estimates from the ship-platform model, and modest improvement in the precision of the aerial-platform model. The combined model had relatively low predictive power, which previous research indicates is primarily a consequence of the dynamic marine environment. We show that the DSM approach presents a flexible framework for developing spatially explicit models of a marine bird from different survey protocols.

Stopover ecology of American Golden-Plovers (Pluvialis dominica) in Midwestern agricultural fields
Full Access

Kirk W. Stodola, Benjamin J. O'Neal, Mark G. Alessi, Jill L. Deppe, Tyson R. Dallas, Tara A. Beveroth, Thomas J. Benson, and Michael P. Ward
pg(s) 162–172


Stopover locations represent critical habitat in the life cycle of migratory birds and the alteration of this habitat can profoundly influence a population. American Golden-Plovers (Pluvialis dominica) migrate though the Midwestern United States each spring, where most natural habitat has been converted to row crop agriculture. We investigated the stopover ecology of the golden-plover in the agricultural matrix of east-central Illinois and west-central Indiana between 2008 and 2012. We found that golden-plovers remained in the region for ∼45 days and individuals spent on average 24 days in the area before departing to the northwest. During a period of peak migration, golden-plovers preferred fields with standing water and, to a lesser extent, soybean fields. Over the 45-day stopover duration, golden-plovers moved extensively (shown by a dynamic occupancy model and area used estimation), with some evidence for tilled fields becoming unoccupied at greater rates than untilled fields. The tendency to use fields with standing water and the movement of individuals from tilled fields suggests that food accessibility, rather than food abundance, is likely a critical factor associated with the prolonged stay, movement, and field type selection of golden-plovers. Food accessibility is important to the golden-plover because they undergo molt into breeding plumage in the region and must refuel for the next leg of their migration. The Midwest is a key stopover location for American Golden-Plovers and promoting foraging conditions by manipulating the drainage of agricultural fields, via the temporary blockage of drain tiles, should be a management focus.
Abstract & References : Full Text : PDF (318 KB) 

Nesting ecology of Marbled Murrelets at a remote mainland fjord in southeast Alaska 

Blake A. Barbaree, S. Kim Nelson, Bruce D. Dugger, Daniel D. Roby, Harry R. Carter, Darrell L. Whitworth, and Scott H. Newman
pg(s) 173–184


Studying the ecology of endangered species in portions of their range where the population remains abundant can provide fundamental information for conservation planners. We studied nesting by radio-tagged Marbled Murrelets (Brachyramphus marmoratus) during 2007 and 2008 in Port Snettisham, a relatively pristine, remote mainland fjord in southeast Alaska with high at-sea densities of Marbled Murrelets during the breeding season. Of 33 active Marbled Murrelet nest sites located during the study, we found 15 within forested habitat (tree nest sites), 16 in nonforested habitat (ground nest sites), and 2 that could not be determined. Some nests were located farther inland from the coast (range: 1–52 km) and at higher elevations (range: 42–1,100 m) than previously documented in Alaska. Nesting success to ≥20 days posthatch (0.20 ± 0.07 [SE]) was less than half of similar estimates in British Columbia and more comparable to estimates from California and Washington. A logistic regression found that nesting success did not differ between years, but nesting success was higher for tree nests than for ground nests. Conservation planners should consider that Marbled Murrelets will use certain nonforest habitat types for nesting in mainland southeast Alaska. Our reported nesting success was likely a maximum, and our results indicate that nesting success can be low even when nesting habitat is seemingly abundant and marine habitat appears excellent.
Abstract & References : Full Text : PDF (827 KB) 

Marbled Godwit migration characterized with satellite telemetry Full Access

Bridget E. Olson, Kimberly A. Sullivan, and Adrian H. Farmer
pg(s) 185–194


Marbled Godwits (Limosa fedoa) breed in 3 disparate areas: The majority breed in the prairies of midcontinental North America, but there are also 2 small and widely separated tundra-breeding populations, 1 in eastern Canada and 1 on the Alaska Peninsula, USA. The major winter ranges include the Atlantic, Pacific, and Gulf coasts of the USA and Mexico. Bear River Migratory Bird Refuge at Great Salt Lake, Utah, USA, is a major stopover site, hosting large godwit populations in the spring and fall. Although the distributions of Marbled Godwit populations and their habitats across the landscape are generally known, the linkages between them are not. We tracked 23 Marbled Godwits equipped with satellite transmitters from sites in Utah, Mexico, Canada, and coastal Georgia during 2006–2010. Our goals were to characterize the migration strategy of Marbled Godwit populations and to determine migratory connectivity of major breeding, staging, and wintering areas. We found that: 1) godwits breeding in the western USA and Canada followed an overland route to winter sites in Mexico after departing their Utah stopover site; 2) godwits tagged in eastern Canada migrated across the continental USA and wintered at sites along the Gulf of California, Mexico; and 3) godwits wintering in coastal Georgia bred in North and South Dakota. We believe this to be the first demonstration of a continental “crisscross” migration pattern in a shorebird. We identified differences in migration elements such as distances traveled, timing of migration, duration, residency, and stopover strategy between the subpopulations, but not between males and females.
Abstract & References : Full Text : PDF (489 KB) 

The role of landscape features and density dependence in growth and fledging rates of Piping Plovers in North Dakota, USA Full Access

Michael J. Anteau, Mark T. Wiltermuth, Mark H. Sherfy, Terry L. Shaffer, and Aaron T. Pearse
pg(s) 195–204


For species with precocial young, survival from hatching to fledging is a key factor influencing recruitment. Furthermore, growth rates of precocial chicks are an indicator of forage quality and habitat suitability of brood-rearing areas. We examined how growth and fledging rates of Piping Plover (Charadrius melodus) chicks were influenced by landscape features, such as hatchling density (hatchlings per hectare of remotely sensed habitat [H ha−1]), island vs. mainland, and wind fetch (exposure to waves) at 2-km segments (n = 15) of Lake Sakakawea, North Dakota, during 2007–2008. Hatchling growth was comparable with published estimates for other habitats. Models for fledging rate (fledged young per segment) assuming density dependence had more support (wi = 96%) than those assuming density independence (wi = 4%). Density-dependent processes appeared to influence fledging rate only at densities >5 H ha−1, which occurred in 19% of the segments we sampled. When areas with densities >5 H ha−1 were excluded, density-dependence and density-independence models were equally supported (wi = 52% and 48%, respectively). Fledging rate declined as the wind fetch of a segment increased. Fledging rate on mainland shorelines was 4.3 times greater than that on islands. Previous work has indicated that plovers prefer islands for nesting, but our results suggest that this preference is not optimal and could lead to an ecological trap for chicks. While other researchers have found nesting-habitat requirements to be gravelly areas on exposed beaches without fine-grain substrates, our results suggest that chicks fledge at lower rates in these habitats. Thus, breeding plovers likely require complexes of these nesting habitats along with protected areas with fine, nutrient-rich substrate for foraging by hatchlings.
Abstract & References : Full Text : PDF (363 KB) 

Landscape and regional context differentially affect nest parasitism and nest predation for Wood Thrush in central Virginia, USA Full Access

Matthew A. Etterson, Russell Greenberg, and Tom Hollenhorst
pg(s) 205–214


Many empirical studies have shown that forest-breeding songbirds, and Neotropical migrants in particular, suffer greater rates of nest predation and nest parasitism in smaller forest patches and in fragmented landscapes. To compare the performance of different metrics of spatial habitat configuration resulting from deforestation, we studied nest predation and nest parasitism rates at 200 Wood Thrush (Hylocichla mustelina) nests in eight forest fragments ranging from 82 to 9,171 ha in central Virginia, USA. We analyzed nest parasitism rates using logistic regression and we analyzed daily nest predation rates under a multistate competing risks design. For both analyses we compared the performance of 16 covariates, 11 of which related to the spatial configuration of habitat (e.g., patch size, distance to edge, percent core forest in proximity to nest) and 5 of which were unrelated to habitat (e.g., year, serial date, nest height). Distance to agriculture gained the greatest support in analyses of nest predation and suggested that elevated predation rates are manifest primarily within 50 m of edges; at 5, 10, and 20 m, respectively, the estimated predation rates were 87%, 76%, and 68%. In contrast, biogeographic region received the greatest support in analyses of nest parasitism, which also showed increasing rates of Brown-headed Cowbird (Molothrus ater) parasitism with percent agricultural land and road density within 500 m of a nest. Among regions, the greatest difference seemed to be a virtual absence of nest parasitism along the Blue Ridge in the absence of disturbance (agriculture or road incursion) whereas the other two biogeographic regions showed 20–50% rates of nest parasitism as background rates. Interactive models between spatial configuration metrics and region gained little support from nest predation analyses, but considerable support from the nest parasitism analyses, suggesting regional context plays a more important role in nest parasitism than in nest predation at these central Virginia sites.
Abstract & References : Full Text : PDF (234 KB) 

Does flooding influence the types and proportions of prey delivered to nestling Mississippi Kites? Full Access

Scott J. Chiavacci, James C. Bednarz, and Thomas J. Benson
pg(s) 215–225


Mississippi Kites (Ictinia mississippiensis) nesting in the Mississippi Alluvial Valley, USA, have consistently exhibited poor reproductive success, reduced average clutch sizes, and evidence of food stress during brood-rearing, raising concerns about population viability. Unlike populations elsewhere, kites nesting in the bottomland forests of this region face dynamic, anthropogenically altered hydrologic conditions that may be affecting the availability of important prey. Therefore, we quantified nestling diets and examined factors thought to be directly influencing the types and proportions of prey delivered to kite nestlings. Specifically, we sought to identify variables affecting the delivery of annual cicadas, the dominant prey item fed to kite chicks in numerous systems, as cicada emergence from subterranean burrows is known to be delayed by flooding. Using time-lapse video, we documented nestling diets and evaluated predictors of diet variability in east-central Arkansas, USA. We found that the delivery of cicadas increased with day of year, and was greatest during the driest of 4 study years. In contrast, the delivery of dragonflies, the numerically dominant prey item, declined with day of year, but increased with water level, and was lowest during the driest year. Although water level was not a strong predictor of the delivery of cicadas, interannual variation in the pattern of cicada deliveries suggests that flooding reduced the availability of this prey item to kites. Also, despite diverse nestling diets, the provisioning of dragonflies and a variety of other arthropods suggests that kites responded functionally to an absence of cicadas. The temporal patterns in prey deliveries that we detected imply that kite nestling diets in bottomland forests of the Mississippi Alluvial Valley may be influenced by water-level impacts on arthropod phenology and abundance.
Abstract & References : Full Text : PDF (326 KB) 

Land use and climate affect Black Tern, Northern Harrier, and Marsh Wren abundance in the Prairie Pothole Region of the United States Full Access

Greg M. Forcey, Wayne E. Thogmartin, George M. Linz, and Patrick C. McKann
pg(s) 226–241


Bird populations are influenced by many environmental factors at both large and small scales. Our study evaluated the influences of regional climate and land-use variables on the Northern Harrier (Circus cyaneus), Black Tern (Childonias niger), and Marsh Wren (Cistothorus palustris) in the prairie potholes of the upper Midwest of the United States. These species were chosen because their diverse habitat preference represent the spectrum of habitat conditions present in the Prairie Potholes, ranging from open prairies to dense cattail marshes. We evaluated land-use covariates at three logarithmic spatial scales (1,000 ha, 10,000 ha, and 100,000 ha) and constructed models a priori using information from published habitat associations and climatic influences. The strongest influences on the abundance of each of the three species were the percentage of wetland area across all three spatial scales and precipitation in the year preceding that when bird surveys were conducted. Even among scales ranging over three orders of magnitude the influence of spatial scale was small, as models with the same variables expressed at different scales were often in the best model subset. Examination of the effects of large-scale environmental variables on wetland birds elucidated relationships overlooked in many smaller-scale studies, such as the influences of climate and habitat variables at landscape scales. Given the spatial variation in the abundance of our focal species within the prairie potholes, our model predictions are especially useful for targeting locations, such as northeastern South Dakota and central North Dakota, where management and conservation efforts would be optimally beneficial. This modeling approach can also be applied to other species and geographic areas to focus landscape conservation efforts and subsequent small-scale studies, especially in constrained economic climates.
Abstract & References : Full Text : PDF (696 KB) 

Factors affecting Burrowing Owl occupancy of prairie dog colonies Full Access

Kristen M. Alverson and Stephen J. Dinsmore
pg(s) 242–250


Understanding patch dynamics can help scientists better understand metapopulations and the relationships of animals that share a habitat. The Burrowing Owl (Athene cunicularia) is a well-known associate of prairie dog colonies, thereby linking conservation measures that benefit these species. We used occupancy modeling to determine how colony attributes (e.g., size and edge effects) and the loss of prairie dog colonies to sylvatic plague affected the occupancy of those colonies by Burrowing Owls in north-central Montana. We surveyed presence–absence of Burrowing Owls during a 13-yr period (1995–2007) and analyzed the data using a robust-design occupancy model in Program MARK. The proportion of colonies occupied by Burrowing Owls ranged from 0.41 to 0.54 across years while the probability of detecting the owls ranged from 0.22 to 0.92. Contrary to our predictions, colony edge effects and plague epizootics showed only weak or no effects on Burrowing Owl occupancy. Prairie dog colony size had the greatest effect on Burrowing Owl occupancy patterns. Colonization of prairie dog colonies by owls generally increased with colony area, whereas owl extinction initially dropped and then increased as a function of increasing colony area. We found no direct link between Burrowing Owl occupancy of prairie dog colonies and plague history, but our results reaffirmed the importance of colony size. Collectively, this information will help inform future conservation efforts for Burrowing Owls that occupy prairie dog colonies.
Abstract & References : Full Text : PDF (322 KB) 

Identifying carry-over effects of wintering area on reproductive parameters in White-winged Scoters: An isotopic approach Full Access

Kirsty E. B. Gurney, Cindy J. Wood, Ray T. Alisauskas, Mark Wayland, Jean-Michel A. DeVink, and Stuart M. Slattery
pg(s) 251–264


Events during one stage of the annual life cycle of migratory birds can have lasting (i.e. carry-over) effects that influence demographic parameters in subsequent seasons. We studied migratory connectivity and potential carry-over effects in a declining population of sea ducks. We measured stable isotope values of carbon (δ13C) and nitrogen (δ15N) in head feathers to assign breeding White-winged Scoters (Melanitta fusca; hereafter scoters) to either Atlantic or Pacific winter populations. The discriminant function for δ13C and δ15N correctly classified 93% of scoters sampled from these 2 winter areas. We then applied this classification scheme to head feathers of females breeding at Redberry Lake, Saskatchewan, and Cardinal Lake, Northwest Territories, to stratify each breeding population by winter provenance. We evaluated carry-over effects associated with winter location of females breeding in Saskatchewan by testing for differences in (1) nesting phenology, (2) clutch size, (3) mid-incubation body mass, (4) nest success, and (5) concentrations of trace elements contaminants of cadmium (Cd), mercury (Hg), selenium (Se), and lead (Pb) in blood, between strata of putative winter origin. Breeding females from the Atlantic coast had later dates of nest initiation, greater mid-incubation body mass, and also had higher concentrations of Cd (one year only), Pb, and Se, relative to birds from the Pacific. Neither nest initiation date nor mid-incubation body mass, however, were related to contaminant concentrations in blood. We found no differences in clutch size or nest success between putative winter strata. Our study detected carry-over effects in the Saskatchewan population that merit further attention.
Abstract & References : Full Text : PDF (440 KB) 

Nest survival of a long-lived psittacid: Scarlet Macaws (Ara macao cyanoptera) in the Maya Biosphere Reserve of Guatemala and Chiquibul Forest of Belize Full Access

Charles R. Britt, Rony García Anleu, and Martha J. Desmond
pg(s) 265–276


The Scarlet Macaw (Ara macao) is a widely distributed parrot that has suffered reduced abundance and increased isolation in Mesoamerican populations. Understanding environmental and temporal factors that influence nest survival may assist efforts to increase annual recruitment for this species, improving population viability. We examined nest survival of Scarlet Macaws in the Maya Biosphere Reserve of Guatemala and Chiquibul Forest of Belize in 2010. Our results suggest that connecting tree canopies have the greatest negative influence on daily nest survival, reducing the probability of a nest surviving the entire nesting period from 0.89 to 0.42. This is likely due to facilitating nest access to predators. Nine of 20 nests in Belize, but no nests in Guatemala, were poached. The majority of poached nests were located in close proximity to a reservoir, which may facilitate access to nests. Based on previous estimates of nest survival required for this population to remain stable, our 2010 data suggest that the population in Guatemala could be growing, but that poaching has reduced nest survival below the threshold for population stability in Belize. Reducing habitat loss in Guatemala and nest poaching in Belize would most benefit this historically connected population.
Abstract & References : Full Text : PDF (528 KB) 


How ornithological societies can get to work for bird conservation 

Philip C. Stouffer
pg(s) 277
Citation : Full Text : PDF (59 KB) 


A vision for an expanded role of ornithological societies in conservation 

Jeffrey R. Walters, Deborah M. Brosnan, J. Michael Reed, and J. Michael Scott
pg(s) 278–289


Professional societies of biologists, including ornithological societies, have struggled to determine the appropriate way to apply the expertise of their memberships in conservation, largely because of a tension between issue advocacy and pure science. Within societies, some argue for using science to promote conservation, and others worry that such advocacy will render the science less credible in the eyes of decisionmakers. This debate excludes other important applications of science in conservation. We outline a vision for an expanded role of ornithological societies in avian conservation that includes pure science and emphasizes one of these other applications, science arbitration. Science arbitration involves evaluating the science relevant to an issue and providing the results to decisionmakers without taking a position on the outcome. We perceive a great need for science arbitration as judges, politicians, and other decisionmakers typically lack access to current, relevant scientific information in an objective form and as a result must act as their own arbiters despite a lack of appropriate expertise. The ornithological societies are in a unique position to fill this void in the area of avian conservation. We describe an additional role in which the societies may also wish to engage, Honest Broker, which is similar to Science Arbiter but also includes development of policy alternatives based on the science evaluated. We provide examples of the kinds of activities in which we envision the societies engaging, and outline a process for approaching science arbitration as the scholarly activity it should be.
Abstract & References : Full Text : PDF (167 KB) 

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