Steve Kendall

ASSESSING THE DEVELOPMENT OF SHOREBIRD EGGS USING THE FLOTATION METHOD: SPECIES-SPECIFIC AND GENERALIZED REGRESSION MODELS

Abstract ABSTRACT We modeled the relationship between egg flotation and age of a developing embryo for 24 species of shorebirds. For 21 species, we used regression analyses to estimate hatching date by modeling egg angle and float height, measured as continuous variables, against embryo age. For eggs early in incubation, we used linear regression analyses to predict hatching date from logit-transformed egg angles only. For late incubation, we used multiple regression analyses to predict hatching date from both egg angles and float heights. In 30 of 36 cases, these equations estimated hatching date to within four days of the true hatching date for each species. After controlling for incubation duration and egg size, flotation patterns did not differ between shorebirds grouped by mass (≥100 g or <100 g) or taxonomy (Scolopacidae versus Charadriidae). Flotation progressed more rapidly in species in which both adults incubate the clutch versus species in which only one adult incubates the clutch, although this did not affect prediction accuracy. We also pooled all continuous data and created a generalized regression equation that can be applied to all shorebird species. For the remaining three species, we estimated hatching date using five float categories. Estimates of hatching date using categorical data were, overall, less accurate than those generated using continuous data (by 3%–5% of a given incubation period). Our equations were less accurate than results reported in similar studies; data collected by multiple observers and at multiple sites, as well as low sample sizes for some species, likely increased measurement error. To minimize flotation method prediction error, we recommend sampling in early incubation, collecting both egg angle and float height data in late incubation, and developing site- and species-specific regression models where possible.

Influence of human development and predators on nest survival of tundra birds, Arctic Coastal Plain, Alaska

Nest predation may influence population dynamics of birds on the Arctic Coastal Plain (ACP) of Alaska, USA. Anthropogenic development on the ACP is increasing, which may attract nest predators by providing artificial sources of food, perches, den sites, and nest sites. Enhanced populations or concentrations of human-subsidized predators may reduce nest survival for tundra-nesting birds. In this study, we tested the hypothesis that nest survival decreases in proximity to human infrastructure. We monitored 1257 nests of 13 shorebird species and 619 nests of four passerine species at seven sites on the ACP from 2002 to 2005. Study sites were chosen to represent a range of distances to infrastructure from 100 m to 80 km. We used Cox proportional hazards regression models to evaluate the effects of background (i.e., natural) factors and infrastructure on nest survival. We documented high spatial and temporal variability in nest survival, and site and year were both included in the best background model. We did not detect an effect of human infrastructure on nest survival for shorebirds as a group. In contrast, we found evidence that risk of predation for passerine nests increased within 5 km of infrastructure. This finding provides quantitative evidence of a relationship between infrastructure and nest survival for breeding passerines on the ACP. A posteriori finer-scale analyses (within oil field sites and individual species) suggested that Red and Red-necked Phalaropes combined (Phalaropus fulicarius, P. lobatus) had lower productivity closer to infrastructure and in areas with higher abundance of subsidized predators. However, we did not detect such a relationship between infrastructure and nest survival for Semipalmated and Pectoral Sandpipers (Calidris pusilla, C. melanotos), the two most abundant shorebirds. High variability in environmental conditions, nest survival, and predator numbers between sites and years may have contributed to these inconsistent results. We recommend targeted management actions to minimize anthropogenic effects and suggest new research needed on this issue as expanding development is planned for the ACP of Alaska. In particular, we recommend research on demography of key predators and their importance with respect to nest survival, and experimental studies that better address challenges posed by high natural variability.

SHOREBIRD ABUNDANCE AND DISTRIBUTION ON THE COASTAL PLAIN OF THE ARCTIC NATIONAL WILDLIFE REFUGE

Abstract ABSTRACT The coastal plain of the Arctic National Wildlife Refuge hosts seven species of migratory shorebirds listed as highly imperiled or high priority by the U.S. Shorebird Conservation Plan and five species listed as Birds of Conservation Concern by the U.S. Fish and Wildlife Service. During the first comprehensive shorebird survey of the 674 000 ha “1002 Area” on the coastal plain, we recorded 14 species of breeding shorebirds at 197 rapidly surveyed plots during June 2002 and 2004. We also estimated detection ratios with a double counting technique, using data collected at 37 intensively studied plots located on the North Slope of Alaska and northern Canada. We stratified the study area by major habitat types, including wetlands, moist areas, uplands, and riparian areas, using previously classified Landsat imagery. We developed population estimates with confidence limits by species, and estimated the total number of shorebirds in the study area to be 230 000 (95% CI: 104 000–363 000), which exceeds the biological criterion for classification as both a Western Hemisphere Shorebird Reserve Network Site of International Importance (100 000 birds) and a Ramsar Wetland of International Importance (20 000 birds), even when conservatively estimated. Species richness and the density of many species were highest in wetland or riparian habitats, which are clustered along the coast.

Relative Shorebird Densities at Coastal Sites in the Arctic National Widlife Refuge

Abstract. In the first comprehensive survey of post-breeding shorebirds conducted along the remote deltaic mudflat habitats on the coastline of the Arctic National Wildlife Refuge, six species of shorebirds were documented aggregating prior to southbound migration. Energy reserves gained while foraging in these areas may be critical for southbound migration of long-distance migrant shorebirds, but these habitats are vulnerable to potential effects of oil and gas development and climate change. The study objective was to assess the relative density and species composition of shorebirds . Surveys were conducted at 13 major river deltas on the coast between late July and mid-August each year from 2006 to 2010. Double-observer methods were used in 2010 to estimate the detection rate in surveys of randomly-selected transect sections. Shorebird density varied significantly between years and among river deltas. Peak relative density estimates at three deltas, the Jago (247.8 birds/km2), the Kongakut (100.6 birds/km2) and the Hulahula (49.5 birds/km2), were significantly higher than the estimate for the Canning (16.0 birds/km2). Because shorebird density and abundance vary significantly among sites and years, and individuals likely move among multiple sites within a given year, shorebird conservation strategies for these habitats should consider them to be spatially and temporally interconnected.

Mercury exposure and risk in breeding and staging Alaskan shorebirds

ABSTRACT Mercury contamination has become a major concern in the Arctic, where elevated mercury deposition has led to large increases in mercury exposure for some Arctic wildlife over the past century. Chronic mercury exposure in birds is known to reduce reproductive success, which may ultimately result in population declines. Many species of Arctic-breeding shorebirds are declining, and exposure to environmental contaminants, such as mercury, may be an important factor. We quantified mercury exposure in 10 shorebird species breeding and staging in Alaska. We analyzed 229 blood and 73 feather samples collected in 2008–2009 for total mercury concentrations. Mercury in blood represents local exposure, whereas mercury in feathers reflects exposure during feather development. Concentrations of mercury ranged from 0.03 to 2.20 μg g−1 in shorebird blood and from 0.16 to 3.66 μg g−1 in shorebird feathers. Most shorebirds sampled during staging had relatively low blood mercury, but some breeding species had sufficiently high concentrations for potential adverse effects. Overall, blood mercury concentrations of breeding shorebirds differed by moisture content of their predominant foraging habitat, with the highest concentrations found in species using wet to aquatic habitats. We also found variation in mercury concentrations by age class and sex for some species, with females showing lower concentrations than males, but we found no relationship between the amount of mercury in feathers and in blood. The degree of mercury exposure seen in Arctic-breeding shorebirds may be of particular concern when combined with other ecological stressors, such as habitat loss, predation, disturbance, and climate change.

Nest-site selection and nest success of an Arctic-breeding passerine, Smith's Longspur, in a changing climate

ABSTRACT Despite changes in shrub cover and weather patterns associated with climate change in the Arctic, little is known about the breeding requirements of most passerines tied to northern regions. We investigated the nesting biology and nest habitat characteristics of Smiths Longspurs (Calcarius pictus) in 2 study areas in the Brooks Range of Alaska, USA. First, we examined variation in nesting phenology in relation to local temperatures. We then characterized nesting habitat and analyzed nest-site selection for a subset of nests (n = 86) in comparison with paired random points. Finally, we estimated the daily survival rate of 257 nests found in 2007–2013 with respect to both habitat characteristics and weather variables. Nest initiation was delayed in years with snow events, heavy rain, and freezing temperatures early in the breeding season. Nests were typically found in open, low-shrub tundra, and never among tall shrubs (mean shrub height at nests = 26.8 ± 6.7 cm). We observed weak nest-site selection patterns. Considering the similarity between nest sites and paired random points, coupled with the unique social mating system of Smiths Longspurs, we suggest that habitat selection may occur at the neighborhood scale and not at the nest-site scale. The best approximating model explaining nest survival suggested a positive relationship with the numbers of days above 21°C that an individual nest experienced; there was little support for models containing habitat variables. The daily nest survival rate was high (0.972–0.982) compared with that of most passerines in forested or grassland habitats, but similar to that of passerines nesting on tundra. Considering their high nesting success and ability to delay nest initiation during inclement weather, Smiths Longspurs may be resilient to predicted changes in weather regimes on the breeding grounds. Thus, the greatest threat to breeding Smiths Longspurs associated with climate change may be the loss of low-shrub habitat types, which could significantly change the characteristics of breeding areas.

The First Hop: Use of Beaufort Sea Deltas by Hatch-Year Semipalmated Sandpipers

River deltas along Alaska’s Beaufort Sea coast are used by hatch-year semipalmated sandpipers (Calidris pusilla) after leaving their terrestrial natal sites, but the drivers of their use of these stopover sites on the first “hop” of fall migration are unknown. We quantified sandpiper temporal distribution and abundance as related to food resources at three river deltas during the beginning of their fall migration (post-breeding period) to compare the habitat quality among these deltas. We conducted population counts, sampled invertebrates, and captured birds to collect blood samples from individuals for triglyceride and stable isotope analyses to determine fattening rates and diet. Patterns of sandpiper and invertebrate abundance were complex and varied among deltas and within seasons. River deltas were used by sandpipers from late July to late August, and peak sandpiper counts ranged from 1000 to 4000 individuals, of which 98% were hatch-year semipalmated sandpipers. Isotopic signatures from blood plasma samples indicated that birds switched from a diet of upland tundra to delta invertebrate taxa as the migration season progressed, suggesting a dependence on delta invertebrates. Despite differences in diet among deltas, we found no differences in fattening rates of juvenile sandpipers as indicated by triglyceride levels. The number of sandpipers was positively associated with abundance of Amphipoda and Oligochaeta at the Jago and Okpilak-Hulahula deltas; an isotopic mixing model indicated that sandpipers consumed Amphipoda and Oligochaeta at Jago, mostly Chironomidae at Okpilak-Hulahula and Spionidae at Canning. Regardless of the difference in sandpiper diets at the Beaufort Sea deltas, their similar fattening rates throughout the season indicate that all of these stopover sites provide a critical food resource for hatch-year sandpipers beginning their first migration.