Severe declines of waterfowl populations on the Yukon–Kuskokwim Delta (YKD), Alaska, from the 1960s through the mid-1980s, prompted the initiation in 1985 of standardized surveys of the region’s breeding birds. These entailed coordinated annual aerial and ground-based surveys, tiered by area and intensity of coverage, which have provided data for this area critical to waterfowl production. Aerial surveys were used to provide broad-scale indices of breeding pairs and the total bird population along the YKD’s entire coast, while ground surveys provided finer-scale estimates of breeding chronology, egg production, nesting effort, habitat use, and predation within core breeding habitats. The extensive coverage of the aerial surveys also provided objective data for expansion of the ground-based sampling, while the nest surveys contributed to a better understanding of aerial survey data, including indices of detection rates. Here we describe patterns of long-term population growth of the Cackling Goose (Branta hutchinsii minima), Greater White-fronted Goose (Anser albifrons frontalis), and Emperor Goose (Chen canagica) relative to population objectives for the Pacific Flyway. We also describe significant growth in the western Alaska population of the Spectacled Eider (Somateria fischeri) following the species’ listing as threatened under the Endangered Species Act in 1993. Growth rates of population indices were positive for the four species from 1985 to 2014, but rates varied within this interval. We found no evidence that dates of nest initiation and hatching advanced significantly between 1985 and 2014. The proportion of waterfowl recorded as pairs by aerial survey crews was correlated with the surveys’ start date for geese but not for the Spectacled Eider. The ratio of nests to aerially observed pairs was 4.8 for Cackling Geese, 5.2 for Greater White-fronted Geese, 5.4 for Emperor Geese, and 2.4 for Spectacled Eiders. The nest-to-pair ratio is one tool by which indices based on aerial surveys can be converted to an estimate of the number of breeding pairs. Together these aerial and ground-based surveys provide the information needed to implement waterfowl management and recovery plans, assess waterfowl distribution across the YKD, measure nesting chronology relative to changes in climate, develop indices to detection rate in aerial surveys, and assess waterfowl vulnerability.

Rapid physical changes that are occurring in the Arctic are primary drivers of landscape change and thus may drive population dynamics of Arctic-breeding birds. Despite the importance of this region to breeding and molting waterbirds, lack of a comprehensive analysis of historic data has hindered quantifying avian population change. We estimated distribution, abundance, and spatially explicit population trend of 20 breeding waterbird species using 25 years (1992-2016) of aerial survey data collected on the Arctic Coastal Plain (ACP), Alaska. The ACP is an extensive wetland complex on Alaska's North Slope that supports millions of breeding waterbirds and includes portions of the National Petroleum Reserve-Alaska and the Arctic National Wildlife Refuge. We summarized annual counts into approximately 6-km by 6-km grid cells and analyzed data with generalized linear mixed models that accounted for survey timing and spatio-temporal autocorrelation. Geese and swans were most abundant along the coast between Admiralty Bay and Prudhoe Bay. Sea ducks, generalist predators (i.e., jaeger, gulls, terns), and loons were most abundant between Utqiaġvik and Point Lay, Alaska. Important areas for most species included the coastal fringe near Teshekpuk Lake, the Colville River Delta, and Admiralty Bay. The National Petroleum Reserve-Alaska was an important area for all species examined. Conversely, density on the coastal plain of the Arctic National Wildlife Refuge was greater than average for 20% of species. Annual population growth rates over the 25-year survey period were variable: 13 increased (range: 1.4%-13.8%), one decreased (-3.4%), and six were stable. However, even species with no overall population trend had areas of changing population size, suggesting localized conditions affected waterbird distributions on the ACP. Our results can be used to better inform land use decisions, improve monitoring of waterbird populations, and increase understanding of avian response to ecological change in the Arctic. Changements spatio-temporels chez des populations d'oiseaux aquatiques nichant dans la Plaine côtière arctique de l'Alaska RÉSUMÉ. Les changements physiques rapides qui se produisent dans l'Arctique figurent parmi les premiers facteurs responsables des changements qui surviennent dans le paysage, et pourraient donc déterminer la dynamique des populations d'oiseaux nichant dans l'Arctique. Malgré l'importance de cette région pour la nidification et la mue des oiseaux aquatiques, l'absence d'une analyse complète des données historiques a freiné la quantification des changements advenus dans les populations d'oiseaux. Nous avons estimé la répartition, l'abondance et la tendance des populations de façon explicite spatialement chez 20 espèces d'oiseaux aquatiques au moyen de 25 années (1992-2016) de données issues de relevés aériens menés sur la Plaine côtière arctique (PCA), en Alaska. La PCA est un vaste complexe de milieux humides dans la région de North Slope en Alaska et supporte des millions d'oiseaux aquatiques nicheurs...

We modeled yellow-billed loon (Gavia adamsii) habitat preferences in a 23,500 km 2 area of northern Alaska using intensive aerial surveys and landscape-scale habitat descriptors. Of the 757 lakes censused, yellowbilled loons occupied 15% and Pacific loons (G. pacifica) 42%. Lake area, depth, proportion of shoreline in aquatic vegetation, shoreline complexity, hydrological connectivity (stream present within 100 m or absent), and an area-connectivity interaction were positive, significant predictors of yellow-billed loon presence in a multivariate logistic regression model, but distance to nearest river or Beaufort Sea coast were not. Predicted yellow-billed loon presence was 13 and 4.7 times more likely on deep and medium lakes, respectively, than on shallow lakes that freeze to the bottom. On small lakes (<60 ha), predicted yellowbilled loon presence was 4.8-1.7 times more likely on lakes with hydrological connectivity than without, but connectivity was not important at most lake sizes (65-750 ha). Yellow-billed loon broods depend on fish available in the brood-rearing lake, and we suggest that a dependable supply of fish is more likely in larger lakes, those deep enough to have open water under winter ice, and those near streams. Highly convoluted shorelines and those with aquatic vegetation provide loon nesting and brood-rearing sites, as well as fish habitat. Pacific loon absence was a significant, positive predictor when added to the habitat model, indicating that yellow-billed loons were four times more likely on lakes without Pacific loons.

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The Yukon–Kuskokwim Delta of Alaska, USA is a globally important region for numerous avian species including millions of migrating and nesting waterbirds. However, data on the current spatial distribution of critical nesting areas and the importance of environmental variables in the selection of nest locations are generally lacking for waterbirds in this region. We modeled nest densities for 6 species of geese and eiders that commonly breed on the Yukon–Kuskokwim Delta, including cackling goose (Branta hutchinsii minima), emperor goose (Chen canagica), black brant (B. bernicla nigricans), greater white‐fronted goose (Anser albifrons frontalis), spectacled eider (Somateria fischeri), and common eider (S. mollissima). The data used were from single‐visit nest searches on 2,318 plots sampled during 29 years from 1985 to 2013. We modeled nest density for each species by combining data across years and using random forests methods and time‐static landscape environmental variables. These models provide the first habitat‐specific predictive distributions of nest density for these species breeding on the Yukon–Kuskokwim Delta of Alaska. Predictive performance of the random forests models varied among species, explaining 13–69% of the variance in nest density. For most species, nest density was greatest near the coast and within lowland habitats. Predicted nest densities mapped across the coastal zone of the Yukon–Kuskokwim Delta revealed areas of high and low nest densities that can be used to inform management and conservation decisions. © 2017 The Wildlife Society.