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At least 37 records · Page 2Linked to original sources
USGS2026

Site fidelity of American Oystercatcher Haematopus palliatus in the Cape Romain Region, South Carolina, United States of America

Site fidelity of American Oystercatchers Haematopus palliatus to both high-tide roosts and nesting habitats remains less-well studied than other aspects of their ecology. During high tides, shorebirds concentrate at roosts primarily to sleep and preen, and the loss of high-quality roost habitat has been linked to population declines in several species. Similarly, high-quality nesting habitat reduces risks from predation, flooding, and intraspecific competition. Strong site fidelity provides additional benefits by allowing individuals to become familiar with local resources and threats. We evaluated intra- and inter-annual fidelity to nonbreeding roosts, fidelity to breeding sites, and natal philopatry in a largely undeveloped coastal landscape, the Cape Romain Region in South Carolina. This region supports one of the largest resident breeding populations of American Oystercatchers along the Atlantic coast of the USA and roughly one third of the nation’s wintering population. From 2001–2014, on 713 days, we banded 290 adults and 141 chicks and conducted resighting surveys during spring high tides across beaches and shell rake roosts. Both resident and migrant birds exhibited strong fidelity to nonbreeding sites, while resident birds were even more faithful to their breeding locations. The mean distance between successive nest sites was just over 1 km, compared to an average shift of about 3 km among nonbreeding sites (maximum 43 km). Movements between breeding and nonbreeding sites averaged approximately 4 km. Natal fidelity was also high: birds first observed paired on a breeding site did so on average 5 km from their natal site (maximum 18 km), at a mean age of 5 years. In a region characterized by abundant oyster-reef foraging habitat and low disturbance, these patterns likely reflect the predictability of prey resources and the availability of protected roosts.

South Carolina↗
USGS2018

Are prey remains accurate indicators of chick diet? A comparison of diet quantification techniques for Black Oystercatchers

The quantification of prey remains is a common method for estimating the diet of a variety of birds. However, these estimates may be subject to biases based on prey body type, nesting habitat, and collection date. To better understand biases and limitations associated with this method, we compared it with two others commonly used to characterize diet: direct observation of parents feeding young and diet reconstruction by stable isotope analysis. In 2013-14, we monitored the diet of 20 Black Oystercatcher broods in south-central Alaska using all three methods, having collected 2126 prey remains, observed 1979 prey items fed to chicks, and obtained stable isotopes values of 39 blood samples from 22 chicks. Direct observations and stable isotope techniques similarly characterized diet composition but these approaches yielded different results from those obtained using prey remains. Soft-bodied prey, such as worms, were not detected in prey remains, and filter-feeders were under-represented. For example, mussels and barnacles, which have flesh that can be removed without having to detach the shell from the substrate, were underestimated using prey remains (mussels: 33% for prey remains vs. 44%, 43% for observations and stable isotopes, respectively; barnacles: 2% vs. 9%, 8%, respectively). On rocky islands, where chicks are confined to a small area around the nest, there were significantly greater quantities of prey remains constituting different diets than on gravel beaches, where chicks leave the nest site within days of hatching. For researchers using prey remains to monitor diet, we suggest that they combine this method with direct observations or stable isotope analysis to understand what prey items may be missed or under-represented.

Alaska↗
USGS2018

Will increased storm surge frequency impact food availability for Semipalmated Sandpipers (Calidris pusilla) at the beginning of fall migration?

Hatch-year Semipalmated Sandpipers ( Calidris pusilla ) use river deltas along the Beaufort Sea as their first stops during fall migration. However, these sites are subject to extreme changes in water levels that affect available foraging habitat. We examined relationships between timing of fall migration and storm surges, with respect to forage availability, using different water level scenarios to predict impacts on food availability for fueling migration at three river deltas. We compared available calories at observed water levels to modeled values derived from changes due to lunar tides (35% decline) and storm surges (58% decline). Peak use by shorebirds varied temporally among sites, while the peak in forage availability occurred late in the season, mismatched with the largest peak in migration at the most used river delta. Shifts in breeding phenology due to climate warming may allow shorebirds to migrate earlier and miss some storm surges, but this may create a mismatch between peak migration and greater food availability. Additionally, changes in climate will likely increase frequency and severity of storm surges that negatively impact availability of foraging habitat for migrant shorebirds.

Wader Study↗
USGS2020

Through thick and thin: Sexing Bristle-thighed Curlews Numenius tahitiensis using measures of bill depth

Birds often exhibit diagnostic traits that differ among individuals of the same species with regard to factors like sex, age, or breeding status. Shorebirds exhibit a wide diversity of colors, shapes, and sizes of their bills, and these traits are commonly used to determine the sex of individuals. In curlews (genus Numenius), length alone accurately separates the sexes in some species, but the shape of the bill has not typically been assessed for this purpose. We collected a suite of measurements on the bills of known-sex Bristle-thighed Curlews N. tahitiensis and determined that standardized measurements of bill depth separated the sexes with high accuracy. A model incorporating the length of a bird’s diagonal tarsus and multiple measurements of the bill was 93.1% accurate in predicting the sex of individual Bristle-thighed Curlews. Simpler models involving only the values of the bill depth near the tip and the base of the bill, however, produced similarly accurate results and are preferred for their parsimony. We advocate the use of one such model that is 93.4% accurate in determining the sex of Bristle-thighed Curlews. As a simple heuristic, a value for the ratio of the bill depth near the tip to that at the base of >0.5 indicated a female, providing an easy field calculation to help determine the sex of Bristle-thighed Curlews. In general, the bills of female Bristle-thighed Curlews are deeper and taper relatively less than those of males. Other observers have qualitatively noted apparent sex-specific differences in the shape of curlew bills, but the generality of our quantitative findings remains to be examined in other curlew species.

Wader Study↗
USGS2021

The Southeastern U.S. as a complex of use sites for nonbreeding rufa Red Knots: Fifteen years of band-encounter data

Shorebirds have been banded for decades and monitoring programs have helped to accumulate large band-encounter datasets from across the globe; however, many of these datasets are left largely unused, particularly those collected by citizen scientists. These datasets can provide valuable insight into the migration and movement strategies of shorebirds and the threats they face throughout their migratory cycle. We used long-term (2003–2018) band-encounter data of Red Knots Calidris canutus rufa in North America to determine: (1) the spatiotemporal distribution during the nonbreeding season, (2) site fidelity to nonbreeding sites, and (3) migratory connectivity of knots using the southeastern United States (Southeast), an important overwintering and stopover area for this subspecies. Annual mean site fidelity ranged from 0% to 86% across 24 sites. We found movement between sites across the Southeast during migratory and wintering periods, indicating that knots are using the region as interconnected sites, as opposed to relying on a single site or a cluster of adjacent sites. We identified ‘hop migration’ as a common strategy for knots in the region, and showed regular within-year movement between sites in South Carolina, Georgia, and Florida. The Southeast is an understudied part of the rufa range; our results show the importance of the region to the subspecies both as a stopover and wintering area. Despite the inherent biases in the data and imperfect detection due to inconsistent survey effort, the data showed large-scale movements and confirmed the region as a complex of sites connected by knots.

Wader Study↗
USGS2022

An evaluation of the reliability of plumage characters for sexing adult Ruddy Turnstones Arenaria interpres morinella during northward passage in eastern North America

We used two datasets to investigate the reliability of plumage for sexing adult Ruddy Turnstones Arenaria interpres of the morinella subspecies during May and early June in Delaware Bay, on the Mid-Atlantic Coast of the United States (39.1202°N, 75.2479°W). We first examined 23 years of data on the capture and recapture of 1,818 individual Ruddy Turnstones to assess the consistency of observers with varying levels of expertise in assigning sex using plumage criteria. Among birds recaptured once, the sex recorded for about 10% differed between captures. This increased to about 16% among birds recaptured more than once. Significantly more birds sexed as females early in the season (during 1–12 May) were later sexed as males than vice versa . This suggests that early-season captures may include birds still in non- (or partial) breeding plumage, which can be confused with female breeding plumage. Second, we compared plumage-based and genetic assessments of sex for 66 Ruddy Turnstones captured in Delaware Bay on 29 May 2016 and 19 May 2017; these individuals were sexed in the hand by an expert on shorebird plumages. Plumage-based and molecular assessments differed in only one case. This suggests that fewer birds will be wrongly sexed on plumage if more care is taken and better instruction is given to observers (including how to distinguish non- breeding plumage from female breeding plumage). We suggest simple procedures to reduce field-sexing errors for Ruddy Turnstones based on plumage.

Delaware, New Jersey, Pennsylvania↗
USGS2025

Evaluating effects of tracking device attachment methods on Black Oystercatchers Haematopus bachmani

Advances in tracking technology are greatly improving our understanding of many aspects of avian ecology. However, the diversity of tracking devices and attachment methods necessitates better evaluation of how they affect particular taxa. We evaluated effects of tracking devices mounted on leg bands or attached using leg-loop harnesses on resighting rates of Black Oystercatchers Haematopus bachmani in Alaska and British Columbia. In Alaska, in 2019, geolocators were mounted on a leg band (n = 20) or encased in a nylon mount and attached using a leg-loop harness (n = 20), and GPS devices were attached using a leg-loop harness (n = 6). In British Columbia, Argos-PTT satellite transmitters were attached using a leg-loop harness (n = 26) in 2019 and 2020. Control birds were colour-banded (Alaska: n = 22; British Columbia: n = 27) but were not equipped with a tracking device. Surveys to resight birds with and without tracking devices were conducted in 2020 and 2021. Birds carrying geolocators, GPS devices, and Argos-PTT satellite transmitters attached using a leg-loop harness were as likely to be resighted (69% in Alaska and 62% in British Columbia) as control birds (59% in both areas). However, birds carrying geolocators mounted on leg bands were far less likely to be resighted (15%). We also used resighting data and a time-to-tag failure analysis to obtain a minimum annual survival estimate for the birds carrying an Argos-PTT satellite transmitter. The minimum annual survival estimate for these birds (0.81 ± 0.08 SE) did not differ from previously reported annual apparent survival estimates for Black Oystercatchers in British Columbia (0.91 ± 0.02 SE). These findings suggest that while Black Oystercatchers can successfully carry tracking devices weighing less than 3% of their body mass when attached using a leg-loop harness, they are negatively affected by small tracking devices mounted directly on leg bands.

Wader Study↗
USGS2003

Monitoring the shorebirds of North America: Towards a unified approach

The Program for Regional and International Shorebird Monitoring (PRISM) has recently developed a single blueprint for monitoring shorebirds in Canada and the United States in response to needs identified by recent shorebird conservation plans. The goals of PRISM are to: (1) estimate the size of breeding populations of 74 shorebird taxa in North America; (2) describe the distribution, abundance, and habitat relationships for these taxa; (3) monitor trends in shorebird population size; (4) monitor shorebird numbers at stopover locations, and; (5) assist local managers in meeting their shorebird conservation goals. The initial focus has been on developing methods to estimate trends in population size. A three-part approach for estimating trends includes: (1) breeding surveys in arctic, boreal, and temperate regions, (2) migration surveys, and (3) wintering surveys.

Wader Study Group Bulletin↗
USGS2001

Winter distributions of North American Plovers in the Laguna Madre regions of Tamaulipas, Mexico and Texas, USA

To determine the distribution and abundance of wintering plovers in the Laguna Madre of Texas and Tamaulipas, surveys were conducted in December 1997 and February 1998, along a 160 km stretch of barrier islands in Mexico and- 40 km of shoreline on South Padre Island, Texas. Altogether, 5,673 individuals, representing six plover species, were recorded during the surveys. Black-bellied Plovers Pluvialis squatarola were the most numerous (3 ,013 individuals) representing 53% of the total number of plovers observed. Numbers of Piping Charadriusm elodu, Snowy C . alexandrinus, Semipalmated C. semipalmatus and Wilson's Plovers C. wilsonia were 739, 1,345, 561, and 13 birds, respectively. Most individuals (97%) of all species except Wilson's Plovers were observed on bayside flats of the barrier islands. Similar numbers of Piping Plovers were recorded at South Padre Island, Texas, and in the Laguna Madre de Tamaulipas. Over 85% of the individuals of each of the other species were found in the more extensively surveyed Mexico portion of Laguna Madre. In Tamaulipas, most plover species were observed more often on algal flats than any other substrate. These results provide evidence of the value of these systems as wintering areas for plover species and indicate the need for more extensive survey efforts to determine temporal and spatial variation in the distribution of these species within the Laguna ecosystem.

Wader Study Group Bulletin↗
USGS2014

A global assessment of the conservation status of the American Oystercatcher Haematopus palliatus

The American Oystercatcher Haematopus palliatus is the most widely distributed of the four oystercatcher species in the Western Hemisphere. Its range covers almost the entire Atlantic Coast from northeastern United States to southern Argentina; on the Pacific Coast it is found from northern Mexico to central Chile. This assessment covers the entire range of the species, and is not intended to serve as a substitute or update for conservation plans that cover the U.S. Atlantic and Gulf Coast populations. Readers are advised to refer to those plans, available at www.whsrn.org, for more detailed information about U.S. populations. The subspecific taxonomy of H. palliatus is far from clear, but five races are recognized in this assessment, primarily to facilitate reference to specific populations (Fig. 1). These are nominate H. p. palliatus (coasts of eastern and southern United States; eastern Mexico; Pacific and Caribbean coasts of Central America; the Caribbean; and northern and eastern South America); H. p. frazari (Gulf of California and western Mexico); H. p. pitanay (coast of western South America); H. p. durnfordi (coast of southeast South America) and H. p. galapagensis (Galapagos Islands). The Galapagos race may deserve species status. Based on a review of existing population estimates and an extrapolation of data from quantitative surveys throughout its range, revised estimates are given for the populations of all five subspecies, and a total population of about 43,000 individuals. The nominate race is the most abundant with an estimated population size of about 20,000 individuals, while the least abundant is H. p. galapagensis , with just 300 individuals estimated. Biogeographic population estimates were used to determine 1% threshold levels and identify sites of regional and global conservation importance. A total of 20 sites have been identified for H. p. palliatus , 5 for H. p. frazari , 10 for H. p. pitanay and 10 for H. p. durnfordi . No key sites were identified for H. p. galapagensis as it is found in low density scattered throughout the islands. Of these 45 sites, 14 have counts that surpass the 1% level of the global population, and are thus of global conservation significance for the species. Because the species is a dispersed breeder, the 1% threshold is of limited value in identifying key breeding sites. For the time being, these have been defined as sites holding 20 or more breeding pairs; 17 such sites have been identified, with all but four in the United States. It is hoped that a more rigorous approach for identifying key breeding sites can be developed in the future. As an obligate coastal species, American Oystercatcher is at risk from widespread habitat loss due to coastal development, and recreational activities that lead to nest disturbance and increased predation. This is exacerbated by the species’ low population size and low reproductive success. Climate change also poses a significant future threat, especially with regard to sea-level rise. To address these threats, conservation actions are proposed that focus on increased legal protection for the species and on the conservation of key sites and important habitats. Conservation could include implementing beneficial management practices, such as restoration of nest and roost sites, controlling predation, and reducing disturbance. Education and outreach programs are needed throughout the species’ range, especially for beach users and urban planners. Training programs will be necessary to ensure successful implementation of many of the priority conservation actions. Finally, a key first step in conserving this species across its range is the creation of a H. palliatus Working Group. Modelled after the U.S. American Oystercatcher Working Group this organization could unite researchers, conservationists, and educators from across the hemisphere to foster coordinated research, conservation action, and monitoring as outlined in this assessment.

International Wader Studies↗
USGS2006

Populations estimates of North American shorebirds, 2006

This paper provides updates on population estimates for 52 species of shorebirds, involving 75 taxa, occurring in North America. New information resulting in a changed estimate is available for 39 of the 75 taxa (52%), involving 24 increases and 15 decreases. The preponderance of increased estimates is likely the result of improved estimates rather than actual increases in numbers. Many shorebird species/taxa are considered to be declining: current information on trends indicates negative trends outnumbered increasing trends by 42 to 2, with unknown or stable trends for 31 taxa.

Wader Study Group Bulletin↗
USGS1991

Observations on habitat use, breeding chronology and parental care in Bristle-thighed Curlews on the Seward Peninsula, Alaska

Results from an intensive survey in 1989 of one of the two known breeding localities of Bristle-thighed Curlews Numenius tahitiensis are reported. During the pre-nesting period birds confined most of their activity to two vegetation communities: shrub meadow tundra and low shrub/tussock tundra. During nesting more than half the Curlews seen were observed on shrub meadow tundra, whilst during brood rearing, use of low shrub/tussock tundra continued to decline in importance as birds attending young increased their use of sedge wet meadows. Despite extensive searches no nests were located; however, observations of broods indicated that nest initiation began around 25 May and that hatching occurred during the last week of June. Detailed observations are presented on the formation of four brood-groups, some of which held different combinations of unrelated adults or young. The adaptive significance of this unusual wader behaviour is discussed.

Alaska↗
USGS1999

Bar-tailed Godwits Limosa lapponica in Alaska: A population estimate from the staging grounds

Bar-tailed Godwits Limosa lapponica were surveyed on their staging grounds in Alaska during September 1995 and 1997. The single high count of 94,000 birds closely matched that of counts from New Zealand and south-eastern Australia, the known non-breeding area for most of the baueri subspecies. Numbers recorded on the southern Yukon-Kuskokwim River Delta and at Egegik Bay, a small estuary along the Alaska Peninsula, qualify both areas as Hemispheric Reserves under the Westem Hemisphere Shorebird Reserve Network, as sites within the East Asian-Australian Shorebird Reserve Network, and as Ramsar sites. The breeding origins, destinations, and taxonomic affinities of Bar-tailed Godwits staging on the coast of south-west Alaska need further assessment.

Alaska↗