Pluvialis Dominica Research Articles

The Amazon Basin’s rivers and lakes support Nearctic-breeding shorebirds during southward migration

ABSTRACT Identifying the migration routes and stopover sites used by declining species is critical for developing targeted conservation actions. Long-distance migratory shorebirds are among the groups of birds declining most rapidly, yet we frequently lack detailed knowledge about the routes and stopover sites they use during their hemisphere-spanning migrations. This is especially true for species that migrate through mid-continental regions in the Western Hemisphere. We therefore used satellite transmitters to track 212 individuals of 6 shorebird species during their southward migrations—Pluvialis dominica (American Golden-Plover), Limosa haemastica (Hudsonian Godwit), Tringa flavipes (Lesser Yellowlegs), Calidris subruficollis (Buff-breasted Sandpiper), C. melanotos (Pectoral Sandpiper), and Bartramia longicauda (Upland Sandpiper)—as they crossed the Amazon Basin of South America, a region from which reports of shorebird numbers are increasing but remain relatively rare. Our results make clear that the Amazon Basin provides stopover habitat for a large number of shorebirds: more than 74% of individuals tracked crossing the Amazon Basin stopped over in the region for an average of 2–14 days, with some spending the entire nonbreeding season there. All species selected stopover sites along the region’s many rivers and lakes, while within stopover sites each species exhibited distinct habitat preferences. The timing of stopovers within sub-basins of the Amazon Basin also coincided with periods of low water, when the muddy, shallow water habitats preferred by most shorebirds are likely plentiful. Together, our results highlight the need for detailed investigations into shorebird abundance and distribution within the Amazon Basin, threats to shorebirds within particular subbasins, and links between shorebird conservation efforts and those targeting the myriad other species that inhabit this dynamic, hyper-diverse region.

Predator home range size mediates indirect interactions between prey species in an arctic vertebrate community.

Indirect interactions are widespread among prey species that share a common predator, but the underlying mechanisms driving these interactions are often unclear, and our ability to predict their outcome is limited. Changes in behavioural traits that impact predator space use could be a key proximal mechanism mediating indirect interactions, but there is little empirical evidence of the causes and consequences of such behavioural-numerical response in multispecies systems. Here, we investigate the complex ecological relationships between seven prey species sharing a common predator. We used a path analysis approach on a comprehensive 9-year data set simultaneously tracking predator space use, prey densities and prey mortality rate on key species of a simplified Arctic food web. We show that high availability of a clumped and spatially predictable prey (goose eggs) leads to a twofold reduction in predator (arctic fox) home range size, which increases local predator density and strongly decreases nest survival of an incidental prey (American golden plover). On the contrary, a scattered cyclic prey with potentially lower spatial predictability (lemming) had a weaker effect on fox space use and an overall positive impact on the survival of incidental prey. These contrasting effects underline the importance of studying behavioural responses of predators in multiprey systems and to explicitly integrate behavioural-numerical responses in multispecies predator-prey models.

Historical avifaunal change and current effects of hiking and road use on avian occupancy in a high‐latitude tundra ecosystem

Tourism is increasing in tundra ecosystems across the world, yet its influence on bird communities and its interaction with other drivers of change is poorly known. To help fill this gap, we paired an interview‐based survey of 11 people with local knowledge of Denali National Park and Preserve, with an occupancy study of 15 bird species in relation to road proximity, traffic volume and hiking. Interviewees noted declines in American Golden PloverPluvialis dominica, Arctic TernSterna paradisaea, Long‐tailed JaegerStercorarius longicaudusand Northern WheatearOenanthe oenantheover the past five decades. Our occupancy study confirmed these reports as we detected no Arctic Terns, few Northern Wheatears, and found both plovers and jaegers to be sensitive to hiking. Occupancy of tundra and shrub habitats by American Golden Plover, American Tree SparrowSpizelloides arborea, Lapland LongspurCalcarius lapponicus, Long‐tailed Jaeger and Willow PtarmiganLagopus lagopusdeclined with increasing hiking intensity. We found that occupancy probability of tundra by Horned LarkEremophia alpestrisincreased, while that of the shrub‐tolerant Wilson’s WarblerCardellina pusilladecreased, with distance from the park road. Detection of species varied based on survey length, noise, start time, presence of a trail and date. The knowledge gained from this study reveals a loss in avian diversity over the past few decades that has the potential to cause a shifted baseline syndrome, and ongoing threats of hiking to sensitive tundra‐breeding birds. Park managers should seek to balance human recreation with the needs of sensitive tundra‐breeding birds to further protect species of conservation concern. This may be done by not building new trails in tundra, limiting access to tundra hiking areas during the early breeding season, reducing the spatial extent of hiking by improving maintained trails and designating a single, maintained path in areas with multiple unofficial hiking tracks, educating tourists about tundra‐nesting birds and closing especially important nesting areas to the public.

Timing of Breeding Site Availability Across the North-American Arctic Partly Determines Spring Migration Schedule in a Long-Distance Neotropical Migrant

Long-distance migrants are under strong selection to arrive on their breeding grounds at a time that maximizes fitness. Many arctic birds start nesting shortly after snow recedes from their breeding sites and timing of snowmelt can vary substantially over the breeding range of widespread species. We tested the hypothesis that migration schedules of individuals co-occurring at the same non-breeding areas are adapted to average local environmental conditions encountered at their specific and distant Arctic breeding locations. We predicted that timing of breeding site availability (measured here as the average snow-free date) should explain individual variation in departure time from shared non-breeding areas. We tested our prediction by tracking American Golden-Plovers (Pluvialis dominica) nesting across the North-American Arctic. These plovers use a non-breeding (wintering) area in South America and share a spring stopover area in the nearctic temperate grasslands, located >1,800 km away from their nesting locations. As plovers co-occur at the same non-breeding areas but use breeding sites segregated by latitude and longitude, we could disentangle the potential confounding effects of migration distance and timing of breeding site availability on individual migration schedule. As predicted, departure date of individuals stopping-over in sympatry was positively related to the average snow-free date at their respective breeding location, which was also related to individual onset of incubation. Departure date from the shared stopover area was not explained by the distance between the stopover and the breeding location, nor by the stopover duration of individuals. This strongly suggests that plover migration schedule is adapted to and driven by the timing of breeding site availability per se. The proximate mechanism underlying the variable migration schedule of individuals is unknown and may result from genetic differences or individual learning. Temperatures are currently changing at different speeds across the Arctic and this likely generates substantial heterogeneity in the strength of selection pressure on migratory schedule of arctic birds migrating sympatrically.

Avian assemblages associated with different grasslands managements in cattle production systems in the pampas of Argentina

Modifications in the structure of grasslands have been responsible for the decline of several avian species due to a reduced quality in available habitat. Currently, applications of the herbicide glyphosate have been introduced to promote winter forage production in the Flooding Pampas of Argentina. Rotational grazing has been another technique used to promote winter forage production. Here, we evaluated different grasslands managements in cattle production systems on species richness, composition, and abundance of bird assemblages in grasslands Pampas. We put emphasis on responses of two neartic migratory shorebirds, the Buff-breasted Sandpiper (Calidris subruficollis) and the American Golden Plover (Pluvialis dominica). The three treatments on natural grassland were: (1) paddocks of Ryegrass growth promotion through the application of herbicide glyphosate; (2) paddocks managed with Rotational grazing, and 3) paddocks managed with Continuous grazing. We considered three periods of the breeding cycle of the birds (early, late, post-breeding) for two years (2011/2012, 2012/2013). Vegetation cover lower than 10 cm was greater in both Rotational and Continuous grazing sites in comparison to the ryegrass promotion sites. A NMDS analysis revealed a clear separation in structure of bird communities among the three grazing treatments. The abundance of total birds and of short grassland birds was lower in grasslands with Ryegrass promotion. An indicator species analysis revealed the associations of shorebirds with Rotational and Continuous grazing sites. Grassland management with glyphosate application had an effect on the structure of assemblages of grassland birds in the Flooding Pampas, which was negative particularly with Nearctic migrants of conservation importance.

Američki zlatni vivak Pluvialis dominica (Muller, 1776) - nova vrsta u ornitofauni Srbije

This paper presents the finding of a new bird species in the fauna of Serbia - American golden plover Pluvialis dominica that was recorded at the Ečka fishpond near Zrenjanin city (UTM 34T DR51). Furthermore, a provided morphological description of the observed individual is accompanied by a brief comparative diagnostic analysis of the identification of species from the genus Pluvialis.

Does habitat partitioning by sympatric plovers affect nest survival?

AbstractThe vertical structure and composition of vegetation can influence the quantity and quality of potential nesting sites for birds. Interspecific competition for high-quality nesting habitat may force some individuals into suboptimal habitat and lead to reduced reproductive success, eventually leading to changes in distribution or abundance. Large climate-mediated shifts in vegetation, including the rapid expansion of shrubs onto tundra, are occurring in the Arctic across important breeding grounds of many shorebird species of conservation concern. We investigated effects of vegetation structure and composition on nest-site selection and nest success of sympatrically breeding American Golden-Plovers (Pluvialis dominica) and Pacific Golden-Plovers (P. fulva), which nest along an elevational gradient ranging from coastal tundra meadows to alpine tundra. Both species strongly selected nest sites with less cover of tall shrubs and other tall vegetation than available at random sites within their territories. American Golden-Plovers selected territories and nest sites that were higher in elevation and had more rocky substrates and less graminoid vegetation than those selected by Pacific Golden-Plovers. The daily nest survival rate was equivalent in the 2 species (0.966, 95% CI: 0.955, 0.975) and similar to that found in other Arctic-breeding shorebirds; however, contrary to predictions, nest survival was not associated with habitat features selected for nest sites for either species. Strong selection of open habitat for nest sites suggests that continued climate-related shrub expansion may reduce the amount of suitable breeding habitat for both species, but partitioning along the elevational gradient and differences in body size suggest that impacts may be more severe for Pacific Golden-Plovers. Additional research is needed to determine if differential selection of nesting habitat is related to survival of the adults or their young.

Evaluating the potential impact of bird predation on the SW Atlantic fiddler crab Leptuca uruguayensis

The southernmost permanent population of the fiddler crab Leptuca uruguayensis occurs along the Samborombón Bay (36°22′S, 56°45′W, Argentina), an important feeding site for many bird species, including ruddy turnstones (Arenaria interpres), whimbrels (Numenius phaeopus), grey plovers (Pluvialis squatarola), american golden plovers (Pluvialis dominica) and gull-billed terns (Gelochelidon nilotica). Although all these birds are known to prey on many fiddler crab species worldwide, there is no estimation of their joint predation impacts, probably due to the difficulty in conducting experiments on an appropriate spatial scale. In these situations, computer simulation methods are useful tools. By using Monte Carlo methods and field data, we modeled the decrease of a fiddler crab population due to bird predation. The model found that under current bird occurrences and crab densities, birds do not consume more than 0.03% of the studied fiddler crab populations. Birds only consume more than 10% of the population if crab density is below 0.02 crabs m2, or if bird occurrences are at least 3 orders of magnitude higher than currently observed. Both situations are unlikely, as mean crab density is 140 crabs m2, and bird density is never so high. Furthermore, by monitoring three different fiddler crab patches, we found that bird predation cannot account for temporal density changes, suggesting that other population processes are more important than bird predation. In conclusion, even though fiddler crabs may exhibit strong predator-avoidance behavior, direct lethal effects of bird predation are currently small.

Trophic niches and feeding relationships of shorebirds in southern Brazil

Niche theory predicts that sympatric species should differ in some ecological characteristic, to allow co-existence and reduce competition for key resources. Food is critical on wintering grounds and stopover areas for migratory species that need to accumulate reserves in order to complete their migration. Wetlands of the Rio Grande do Sul coastal plain, in southern Brazil, host several species of shorebirds with similar morphology, foraging methods and diet. When these species are in sympatry, some trophic niche overlap is expected. Diets and trophic niches of migratory and resident shorebirds were investigated during the austral summer on Torotama Island, Lagoa dos Patos Estuary, Brazil. Complementary methods were used to determine the trophic ecology of three shorebird species; diet was determined through analysis of feces and food samples, using stable isotopes of carbon and nitrogen. The local invertebrate community was sampled to determine potential prey and ascertain feeding preferences of birds. Coleoptera was the most abundant taxon in the feces of all shorebirds. Trophic niche overlap in the diets was high, with the widest trophic niche found for the buff-breasted sandpiper Calidris subruficollis. Isotopic mixing models indicated differences in the main food sources of shorebirds. The isotopic niche breadth was widest for the American golden-plover Pluvialis dominica. These species, as well as the resident southern lapwing Vanellus chilensis, consumed some prey in higher proportions over others, although they had generalist diets. Migratory species with generalist habits benefit from heterogeneous environments such as floodplains during the non-breeding season.

Managing Grasslands to Maximize Migratory Shorebird Use and Livestock Production

Grasslands are important to domestic and wild animals. Migratory shorebirds are important components of coastal rangeland ecosystems. Buff-breasted Sandpiper (BBSA, Calidris subruficollis) and American golden-plover (AMGP, Pluvialis dominica) are two insectivorous, migrant shorebirds that rely on livestock-grazed grasslands in the Southern Cone of South America during their nonbreeding season, as well as on migration in North America. We studied habitat selection of these species and contrasted their needs with livestock requirements needed to develop recommendations for grazing management that benefit wildlife and livestock production. Short grass height was positively related to BBSA and AMGP abundance, with ideal grass heights from 2 to 5 cm. However, maximum livestock production is associated with grass height over 6 cm. The amount of forest cover, which is used to provide shade to livestock, was negatively related to the occurrence of both shorebird species, likely due to higher risks of predation. Grassland improvement did not affect BBSA but negatively affected AMGP abundance. Short grass habitat was selected by both shorebird species in spite of the higher arthropod biomass in taller grasslands, suggesting that other factors besides food abundance, such as the ability to detect prey and predators, are driving habitat selection. To enhance shorebird (and other wildlife) conservation and livestock production, we recommend managers adjust grazing intensity so that grass height is > 6 cm from mid-February to September, when the Nearctic migrant shorebirds are absent, and from 2 to 5 cm from October to early February when shorebirds are present. These austral summer adjustments should be restricted to paddocks with low forest cover so that livestock production in paddocks with high forest cover remains maximized. All adjustments should be evaluated by each farmer to ensure adequate economic returns are met.

Shorebird hunting in Barbados: Using stable isotopes to link the harvest at a migratory stopover site with sources of production

ABSTRACT Understanding spatial connectivity of long-distance migrants is important for effective management and conservation of both game and nongame species. Hunting of Nearctic-breeding shorebirds occurs in the Caribbean and northern South America; however, the origins of harvested individuals are generally unknown. We used stable hydrogen isotopes (δ2H) in feathers of juvenile shorebirds to infer the origins of birds harvested at 2 sites in Barbados using probabilistic assignments based on a terrestrial–freshwater δ2H isoscape. We used tissue δ13C and δ15N values to filter individuals that had derived nutrients from marine sources. Natal origins of juvenile American Golden-Plover (Pluvialis dominica), Stilt Sandpiper (Calidris himantopus), Short-billed Dowitcher (Limnodromus griseus), and Lesser Yellowlegs (Tringa flavipes) were predicted to be mainly from the eastern parts of their breeding ranges in eastern Canada, with American Golden-Plover, Stilt Sandpiper, and Short-billed Dowitcher also having h...

Dried blood spots for estimating mercury exposure in birds.

Mercury (Hg) is a pervasive environmental contaminant that can impair avian health, consequently there is a need to gauge exposures. Bird blood provides a measure of recent dietary exposure to Hg, but blood collection and storage can be complex and costly. Dried blood spots (DBS) may help overcome challenges of whole blood analyses, therefore, this study aimed to develop and validate a novel method to assess Hg exposure in birds using DBS. First, accuracy and precision of blood Hg concentrations for entire DBS and DBS punches were determined for white leghorn chicken (Gallus gallus domesticus) dosed with methylmercury (MeHg) via egg injection. Next, we investigated Hg stability in chicken DBS subjected to time, temperature, and humidity treatments. Lastly, we applied the method to DBS created using standard field methods from zebra finch (Taeniopygia guttatato) in the laboratory and American golden-plover (Pluvalis dominica) sampled in the field. All samples were analyzed for total Hg (THg) using direct Hg analysis. Accuracy was determined by comparing DBS concentrations with those of corresponding whole blood and reported as percent recovery. Accuracy for entire chicken DBS was 101.8 ± 5.4%, while DBS punches revealed lower recovery (87.7 ± 4.0 to 92.4 ± 4.1%). There was little effect of time, temperature, and humidity storage treatments on Hg concentrations of DBS, with mean DBS THg concentrations within ±8% of whole blood (n = 10 treatments). For zebra finch, DBS punches were more accurate (93.7 ± 9.7%) compared to entire DBS (126.8 ± 19.4%). While for American golden-plover, entire DBS resulted in the most accurate THg concentrations (111.5 ± 7.6%) compared to DBS punches (edge: 115.4 ± 18.9%, interior: 131.4 ± 16.1%). Overall, results indicate that DBS analysis using direct Hg analysis can accurately evaluate Hg exposure in birds.

Do American Golden-Plovers (Pluvialis dominica) Avoid Wind-energy Turbines in Agricultural Fields in Indiana During Spring Migration?

ABSTRACT.— The American Golden-Plover (Pluvialis dominica), a species of conservation concern, uses large agricultural fields during its spring passage through the mid-western United States. In west-central Indiana, large numbers of golden-plovers make a stopover in corn or soybean fields that were harvested the previous fall. Stopovers last for a number of days during which the birds feed and molt into alternate plumage. In recent years, wind energy facilities have been developed in the area with hundreds of wind turbines erected in fields used by the golden-plovers. During spring 2011 and 2012, we investigated patterns of golden-plover behavior at these facilities in Benton County, Indiana at a site where large spring aggregations of plovers have been observed for many years. Our results showed only limited behavioral avoidance of the turbines, and suggested that wind-energy development in this area was not significantly impacting migrant golden-plovers. However, we caution that additional studies could...

Shorebird Population Estimates Using Seasonal Aerial and Terrestrial Surveys at Samborombón Bay, Argentina

Abstract. Information about shorebirds is essential for predicting the impact of natural and human-mediated changes on their populations. Aerial and terrestrial surveys were performed to characterize shorebird abundance, spatial distribution and assemblage composition at Samborombon Bay, Argentina, during different tide levels and seasons. Approximately 60,000 shorebirds were observed using the intertidal flats. Highest abundances occurred during austral summer, autumn and spring when Nearctic migrants dominate the assemblage. Significant percentages (> 1%) of the populations of three Nearctic migrants [American Golden-Plover (Pluvialis dominica), Hudsonian Godwit (Limosa haemastica), and White-rumped Sandpiper (Calidris fuscicollis)], one Neotropical migrant [Two-banded Plover (Charadrius falklandicus)], and two resident species [American Oystercatcher (Haematopus palliatus) and Black-necked Stilt (Himantopus mexicanus)] were estimated. Large numbers of Semipalmated Plovers (C. semipalmatus), Rufous-ches...

Restoring fire to grasslands is critical for migrating shorebird populations.

Fire is a disturbance process that maintains the structure and function of grassland ecosystems while sustaining grassland biodiversity. Conversion of grasslands to other land uses coupled with altered disturbance regimes has greatly diminished the habitat available to many grassland-dependent species. These changes have been linked to declines in breeding birdpopulations, but may also be critical for migrating bird populations such as those shorebird species that depend on mesic grasslands during migration. We examined migratory shorebird use of burned grasslands in the southern Great Plains of North America using DISTANCE sampling to estimate and compare bird densities across recently burned and not recently burned landscapes (1-5yr post fire). We conducted two surveys per week for 8-10weeks along a 54-km route starting at the end of March and concluding in mid-May during 2014-2015. We encountered 2,509 total shorebirds in recently burned areas compared to 130 individuals in areas that were unburned. Fire was a major attractant for our three focal species with American Golden-plover (Pluvialis dominica), Upland Sandpiper (Bartramia longicauda), and Killdeer (Charadrius vociferus) densities of 20.48, 11.09, and 26.09 birds/km2 in burned areas compared with 0.00, 1.27, and 0.92 birds/km2 in unburned areas, respectively. This research illustrates the importance of burned grassland for migrating shorebirds, a phenomenon that has largely gone unreported previously. Generally, these findings add to a body of knowledge that demonstrates the value of managing grasslands with historic disturbances that vary over space and time. The application of these findings should improve decision-making for shorebird conservation and provides evidence that prescribed fire planning should include consideration for breeding, transient, and non-breeding populations that vary in their temporal use of the landscape.

Is it safe to nest near conspicuous neighbours? Spatial patterns in predation risk associated with the density of American Golden-Plover nests.

Predation is one of the main factors explaining nesting mortality in most bird species. Birds can avoid nest predation or reduce predation pressure by breeding at higher latitude, showing anti-predator behaviour, selecting nest sites protected from predators, and nesting in association with protective species. American Golden-Plovers (Pluvialis dominica) defend their territory by using various warning and distraction behaviours displayed at varying levels of intensity (hereafter “conspicuous behaviour”), as well as more aggressive behaviours such as aerial attacks, but only in some populations. Such antipredator behaviour has the potential to repel predators and thus benefit the neighbouring nests by decreasing their predation risk. Yet, conspicuous behaviour could also attract predators by signalling the presence of a nest. To test for the existence of a protective effect associated with the conspicuous antipredator behaviour of American Golden-Plovers, we studied the influence of proximity to plover nests on predation risk of artificial nests on Igloolik Island (Nunavut, Canada) in July 2014. We predicted that the predation risk of artificial nests would decrease with proximity to and density of plover nests. We monitored 18 plover nests and set 35 artificial nests at 30, 50, 100, 200, and 500 m from seven of those plover nests. We found that the predation risk of artificial nests increases with the density of active plover nests. We also found a significant negative effect of the distance to the nearest active protector nest on predation risk of artificial nests. Understanding how the composition and structure of shorebird communities generate spatial patterns in predation risks represents a key step to better understand the importance of these species of conservation concern in tundra food webs.

Habitat and social factors influence nest-site selection in Arctic-breeding shorebirds

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

Inorganic and organic contaminants in Alaskan shorebird eggs.

Many shorebird populations throughout North America are thought to be declining, with potential causes attributed to habitat loss and fragmentation, reduced prey availability, increased predation, human disturbance, and increased exposure to environmental pollutants. Shorebirds may be particularly vulnerable to contaminant exposure throughout their life cycle, as they forage primarily on invertebrates in wetlands, where many contaminants accumulate disproportionately in the sediments. Therefore, it is important to document and monitor shorebird populations thought to be at risk and assess the role that environmental contaminants may have on population declines. To investigate potential threats and provide baseline data on shorebird contaminant levels in Alaskan shorebirds, contaminant concentrations were evaluated in shorebird eggs from 16 species residing in seven geographic distinct regions of Alaska. Similar to previous studies, low levels of most inorganic and organic contaminants were found, although concentrations of several inorganic and organic contaminants were higher than those of previous studies. For example, elevated strontium levels were observed in several species, especially black oystercatcher (Haematopus bachmani) sampled in Prince William Sound, Alaska. Additionally, contaminant concentrations varied among species, with significantly higher concentrations of inorganic contaminants found in eggs of pectoral sandpiper (Calidris melanotos), semipalmated sandpiper (Calidris pusilla), black oystercatcher, and bar-tailed godwit (Limosa lapponica). Similarly, significantly higher concentrations of some organic contaminants were found in the eggs of American golden plover (Pluvialis dominica), black-bellied plover (Pluvialis squatarola), pacific golden plover (Pluvialis fulva), bar-tailed godwit, and semipalmated sandpiper. Despite these elevated levels, current concentrations of contaminants in shorebird eggs suggest that breeding environments are relatively free of most contaminants and that contaminant concentrations are below levels (except potentially strontium) that would likely affect the survival of individuals and consequently regulate the species at the population level.

Shorebird Seasonal Abundance and Habitat-Use Patterns in Punta Rasa, Samborombón Bay, Argentina

Shorebird assemblage composition and habitat-use patterns were characterized at Punta Rasa during the austral summer, autumn and winter. Compared to other sites within the region, this area showed high species richness, reflected by a total of 22 species recorded within a relatively short time frame. Differences in assemblage structure were driven by the use of estuarine mudflats and oceanic sandy beaches as feeding habitats. During low tide, more species used estuarine environments, achieving the highest total densities. Abundance patterns and assemblage composition also changed seasonally. Maximum total abundance occurred during the austral summer, and minimum total abundance during the austral winter. During the austral summer, the assemblage was dominated by Nearctic migrants such as American Golden-Plover (Pluvialis dominica), Hudsonian Godwit (Limosa haemastica) and White-rumped Sandpiper (Calidris fuscicollis). In addition, Two-banded Plover (Charadrius falklandicus) and American Oystercatcher (Haematopus palliatus) were abundant during the austral autumn. The Red Knot (Calidris canutus), a shorebird that dominated the austral autumn assemblage 25 years ago, was recorded in relatively small numbers during this study, probably reflecting the global population trend of a subspecies of the Red Knot (C. c. rufa) in the past two decades. During the austral winter, resident birds largely dominated the assemblage. However, it is noteworthy that some individuals of nine Nearctic migrant species remained in the area. In the case of the endangered Red Knot, Punta Rasa is, along with Lagoa do Peixe in Brazil, one of the sites in South America with the highest known abundances during the austral winter.

Genetics of a high-latitude cryptic speciation event: American and Pacific golden-plovers

ABSTRACT Diversification during the Pleistocene is thought to have contributed significantly to taxonomic diversity at high latitudes. In some cases this diversity is cryptic, in that speciation has occurred with little change in phenotype. We examined the genetic signatures of one such case, between American and Pacific golden-plovers (Pluvialis dominica and P. fulva, respectively). This high-latitude species pair is morphologically very similar, and they are obligate long-distance migrants. They were only relatively recently recognized as separate species. We used 1,041 bp of the mitochondrial gene NADH dehydrogenase subunit 2 (ND2) from 20 dominica and 22 fulva and 242 amplified fragment length polymorphisms (AFLPs) from 29 individuals of each species sampled from sympatric and allopatric breeding populations to assess the levels of divergence, divergence date, and gene flow. A divergence date of ∼1.8 mya was estimated, and although we detected a seemingly old hybridization event, very little gene flow...