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At least 19 recordsLinked to original sources
USGS1998

Wetland connectivity and waterbird conservation in the western Great Basin of the United States: Introduction to workshop

As scientists, managers and landowners, we have come to realize that to best understand the local and regional value of individual wetlands, we need to take a broad geographic, taxonomic, and management view. In December 1994, a symposium was held in Reno, Nevada that addressed this topic for shorebirds by bringing together researchers and managers from the Western Great Basin to discuss shorebird research and management in the region (Reed et al. 1997, International Wader Studies 9). In February 1998, a similar, but broader, symposium was held in Bend, Oregon that addressed wetland connectivity and waterbird conservation in the Western Great Basin. Over 100 participants spent one day listening to talks from waterbird researchers that focused on multi-scale habitat use and movements of birds in the region. From American Avocets Recurvirostra americana to White Pelicans Pelcanus erythrorhynchos we learned of phenomenal intra-season movements throughout the Basin and the value of collecting detailed data of this nature for representative waterbirds. We learned also about the National Shorebird Conservation Plan and spent the next day in discussion groups where future research and management priorities were outlined. These discussions were the first regional planning effort for the National Plan.

Great Basin↗
USGS2019

Survival of Bristle-thighed Curlews equipped with externally mounted transmitters

Telemetry devices are widely used in avian research, but the degree to which the deployment of such devices affects the survival of study subjects is often not addressed. It is generally assumed that such effects are less pronounced in large-bodied species that conduct relatively short migrations and carry relatively light telemetry devices. We studied Bristle-thighed Curlews Numenius tahitiensis over the period 2012–2017 at a nonbreeding site on the island of Oahu, Hawaii. We used leg-loop harnesses to equip 11 curlews with externally mounted, solar-powered satellite transmitters that constituted ca. 3% of their body mass, and compared the annual survival of these birds to 37 curlews marked only with uniquely engraved leg flags. Despite the species’ large size and the small mass of the transmitters, we documented potential negative effects of externally mounted transmitters on the survival of Bristle-thighed Curlews. We also documented apparent effects of age and sex on the survival of curlews, underscoring the difficulty of disentangling the effects of research techniques on study subjects. Understanding and publicizing the potential effects of research itself on wildlife are crucial steps in the process of refining technical applications and improving the welfare of study animals. We urge researchers to critically assess and report the effects of similar research techniques to minimize deleterious effects in future studies.

Wader Study↗
USGS2016

Nesting ecology of Whimbrels in boreal Alaska

Breeding ecology studies of boreal waders have been relatively scarce in North America. This paucity is due in part to boreal habitats being difficult to access, and boreal waders being widely dispersed and thus difficult to monitor. Between 2008 and 2014 we studied the nesting ecology of Whimbrels Numenius phaeopus hudsonicus in interior Alaska, a region characterized by an active wildfire regime. Our objectives were to (1) describe the nesting ecology of Whimbrels in tundra patches within the boreal forest, (2) assess the influence of habitat features at multiple scales on nest-site selection, and (3) characterize factors affecting nest survival. Whimbrels nested in the largest patches and exhibited a consistently compressed annual breeding schedule. We hypothesized that these Whimbrels would exhibit synchronous and clustered nesting, but observed synchronous nesting in only 2009 and 2011, and evidence of clustered nesting at just one study area in 2009, providing limited support for the hypothesis. Nests tended to be on hummocks and exhibited lateral concealment around the bowl, suggesting a trade-off between a greater view from the nest and concealment. However, our analysis failed to identify other important habitat features at scales from 1–400 m from the nest. Our best-supported nest survival model showed a strong difference between our two main study areas, but this difference remains largely unexplained. Given the increased frequency, severity, and extent of wildfires predicted under climate change scenarios, our study highlights the importance of monitoring the persistence of boreal tundra patches and the Whimbrels breeding therein.

Alaska↗
USGS2026

Post-hatch ecology, diet, and first migration of juvenile Alaskan Bar-tailed Godwits

Life stages between hatching and adult recruitment are poorly described for most migratory shorebird species and represent a critical knowledge gap in understanding long-term population dynamics. We conducted a pilot study on the Seward Peninsula, Alaska, to assess the feasibility of following juvenile Bar-tailed Godwits Limosa lapponica baueri from their breeding grounds to their non-breeding grounds in New Zealand and Australia. Radio-tracked broods were highly mobile and moved hundreds to thousands of meters per day. They used low-elevation wetlands with dense shrub cover when younger, and more open, tundra-dominated ridgetops when older. Using DNA metabarcoding analysis of fecal samples, we found that chick diet consisted largely of flying insects (e.g. Tenthredinidae and Ichneumonidae) and small gastropods and appeared to increase in diversity with chick age. We followed one brood to near-fledging (ca. 26 days old) and deployed 5-g satellite transmitters on three chicks. One of these subsequently moved to the Yukon-Kuskokwim Delta, from where it flew 11 days and an estimated 13,391 km to Tasmania, which is the longest non-stop flight recorded for landbirds. These results provide the first information on the ecology of pre- and post-fledging young Bar-tailed Godwits in Alaska, and will inform future efforts to study this important life stage.

Alaska↗
USGS2020

After-hatch and hatch year Buff-breasted Sandpipers (Calidris subruficollis) can be sexed accurately using morphometric measures

Determining the sex of birds quickly in the field can help in studies of behavior and distribution, and when selecting particular sexes for deploying tracking devices or collecting samples. However, discerning males from females is difficult in species that are plumage monomorphic and have overlapping sexual-size dimorphism, as in Buff-breasted Sandpipers Calidris subruficollis . We developed three discriminant functions to sex Buff-breasted Sandpipers based on measurements of live birds captured in Brazil whose sex was confirmed with molecular techniques. We validated these discriminant functions using morphometric measures from other independent samples of known-sex live birds from wintering (Brazil), migration (Texas), and breeding (Alaska) sites. Discriminant functions derived from birds captured in Brazil accurately sexed ≥88% of the validation sample from Brazil, Texas, and Alaska. Errors in classification occurred among males on the wintering (0–5%) and breeding (8–12%) grounds, and females during migration (0–11%). Discriminant functions worked well because of the substantial sexual size dimorphism present in the species, with male traits being in general 5.2–10.4% larger than female traits. The size of morphological traits did not vary by age (after controlling for sex) for birds sampled on the wintering grounds and during migration. Our results indicate that discriminant functions can be used to sex after-hatch year (AHY) Buff-breasted Sandpipers throughout their range, and for hatch year (HY) birds during their first southbound migration and winter. Being able to accurately sex both AHY and HY birds using only morphological measurements will improve studies of the ecology and population structure of this species and enhance the application of conservation measures.

Wader Study↗
USGS2021

Bar-tailed Godwits Limosa lapponica in Alaska: Revisiting population estimates from the staging grounds

Bar-tailed Godwits Limosa lapponica baueri breed in Alaska and spend the nonbreeding season primarily in eastern Australia and New Zealand. Long-term declines spurred recent surveys at nonbreeding sites that yielded a revised population estimate of ~126,000 godwits. We conducted aerial surveys for Bar-tailed Godwits in 2018 and 2019 at pre-migratory staging sites in western Alaska. Counts from similar surveys in 1997 accorded with counts of baueri from the nonbreeding range. Instead of relying on observer estimates of flock sizes, we enumerated 97% of our survey totals using digital photography. Our survey results differed markedly between 2018 (39,751) and 2019 (100,926), differences that reflected a relatively late autumn survey period in 2018, when some godwits were likely to have left the area, compared to 2019. In contrast to the 1997 surveys, we found few Bar-tailed Godwits at estuaries on the Alaska Peninsula. However, we counted nearly 93,000 godwits (~92% of survey total) along ~60 km of coast at the Kuskokwim River Delta in 2019, a value constituting nearly three-quarters of the subspecies’ current population estimate. Our survey totals for 2019 were in agreement with contemporaneous counts at austral nonbreeding sites, demonstrating how aerial surveys from Alaska can provide useful insights into counts conducted elsewhere in the subspecies’ range. When combined with measures of reproductive output, estimates of seasonal survival, and dedicated studies of the movement and survival of juvenile godwits, future surveys from Alaska can further contribute to efforts to determine mechanisms of population changes in baueri Bar-tailed Godwits.

Alaska↗
USGS2024

Return rates of GPS-tagged Pacific Golden-Plovers: A controlled study in Hawaii

In a study of GPS-tagged Pacific Golden-Plovers wintering at Moorea, French Polynesia, Johnson et al. (2020) raised questions about possible tag-induced mortality. Similar concerns in other species have generated considerable attention in recent years. Of 19 tagged plovers that departed Moorea on northward migration, only one bird (5 %) uploaded a complete migratory cycle to Argos. Furthermore, contact was lost with 12 birds (63 %) variously during overwater flight, at stopover sites, or on nesting grounds; and no signals at all were received from 6 individuals (32%). Such observations suggest that carrying a tag might be a life-threatening burden. We cannot exclude the possibility that tag weight caused difficulties for the Moorea birds. However, this seems an unlikely factor in that the device (tag plus harness) being carried weighed less than 3 % of body mass (see beyond). Such a load is in accord with generally accepted albeit arbitrary limits. Other tag-associated concerns such as altered aerodynamics, increased vulnerability to predation, and (given the complex nature of geomagnetic navigation, the possibility that tag electronics might interfere with sense of direction, are more difficult to evaluate. Alternatively, loss of contact with tagged birds may be simply a matter of tag malfunction, battery failure, or a broken harness. To shed light on these uncertainties, and to explore the survival of GPS-tagged plovers on a nonbreeding ground in Hawaii, we conducted a controlled study using birds that winter in the National Memorial Cemetery of the Pacific (known locally as the Punchbowl).

Hawaii↗
USGS2020

Tracking the migration of Pacific Golden-Plovers from nonbreeding grounds at Moorea, French Polynesia, using Pinpoint GPS-Argos tags

We used Pinpoint GPS-Argos tags to track migration of Pacific Golden-Plovers Pluvialis fulva in 2017 and 2018 from Moorea Island, at the extreme southeastern edge of the species’ winter range. Of 20 tagged birds, 13 uploaded locations during all or part of their northward migration. The birds departed in mid-April traveling a long (8,250–10,200 km) northwestward track. Ten individuals signaled from Japan, where they stopped over (or ‘staged’) for periods up to about one month. Almost all stopovers were on the island of Honshu, with coordinates indicating inland habitats, most likely rice fields. In May, at least nine of the plovers left Japan on a mid-length (3,200–5,400 km) northeastward track to the Bering Sea region, where one bird reported from a possible nesting site in Kamchatka Krai and eight from traditional breeding grounds (three from Chukotka, five from Alaska). Thereafter, contact with tags was intermittent and gradually lost. We received signals from only two individuals during fall migration; one bird flew 1,600 km southeast from Alaska before its tag ceased transmitting, and the other flew >8,600 km directly southward from its post-breeding site in southwest Alaska and made landfall in Samoa where transmissions ended. Throughout the study, lengthy transoceanic flights appeared to be nonstop, and the annual migratory pathway (though defined by only a single bird in fall) was circular. As we have shown in other studies, Japan emerges as a key stopover site for Pacific Golden-Plovers during northward migration.

Wader Study↗
USGS2004

Subarctic, alpine nesting by Bairds Sandpipers Calidris bairdii

Baird's Sandpipers Calidris bairdii were found nesting in alpine habitat in southwestern Alaska (60°48'N, 154°00'W), almost 250 km from the nearest known breeding site, and studied over three consecutive seasons, 1997-1999. The first birds arrived during the second week of May each spring with peak numbers recorded the third week of May. Most nests and newly hatched broods were found on sparsely vegetated dwarf shrub-lichen mat tundra on level or gently sloping areas throughout the alpine zone between 980 and 1400 m above sea level. Most eggs hatched during the third week of June and independent young were noted during the second and third weeks of July. Both parents initially tended broods, but only the male remained after chicks were about four days of age. During early brood-rearing, adults began to move chicks, often to higher elevations and over distances of several hundred metres. Throughout the area the density of nesting birds was about 0.2 pairs/km 2 with up to 0.9 pairs/km 2 found on southerly exposures of the north study slope. A summary of available information revealed the global nesting distribution of bairdii to be strongly associated with disturbed landscapes, especially montane areas affected by glaciation, suggesting the breeding range is likely to be much more extensive than currently known, especially in areas of Alaska, the Yukon, and possibly Chukotka.

Alaska↗
USGS2000

Application of a modified harness design for attachment of radio transmitters to shorebirds

Radio transmitter attachment methodology is important to the design of radio telemetry studies. In 1998, we attached 5 transmitters to a captive population of Western Sandpipers ( Calidris mauri ) and 7 transmitters to wild Killdeer ( Charadriusv ociferus ) using a modified version of the Rappole and Tipton (1991) figure-8 leg-loop harness. Captive birds fitted with harnesses did not exhibit quantifiable differences in behavior relative to control birds. Based on initial success in using the leg-loop harnesses, we used harnesses to attach transmitters in the wild to 30 Killdeer and 49 Dunlin ( Calidris alpina ) during the winters of 1998-1999 and 1999-2000. This was part of a study on movements of wintering shorebirds in the Willamette Valley of Oregon, USA. Wild birds showed no adverse effects of the harnesses.Thus, the described harness is a practical method for attachment of transmitters to shorebirds. Advantages of this harness method include a reduction in handling time at capture, elimination of the need to clip feathers for attachment, and increased transmitter retention time.

Oregon↗
USGS2025

Adult and hatch-year survival and fidelity of Piping Plovers Charadrius melodus in the lower Platte River system, Nebraska, USA

Knowledge of vital rates informs the conservation and management of threatened and endangered species. In the northern Great Plains, USA, the federally threatened Piping Plover Charadrius melodus uses a variety of nesting habitats including natural river sandbars and human-created sites in the lower Platte River system, Nebraska. In this area, off-river sandpit sites (i.e., active sand and gravel mines, transition sites, and lakeshore housing developments) are not managed to prioritize nesting and are often considered inferior habitat to sandbars. However, most Piping Plovers in the lower Platte River system nest off river, especially in years when sandbar habitat is limited. As the quantity of habitat provided at off-river sites is predicted to decline, evaluating vital rates among different off-river nesting habitats will inform future conservation efforts. We estimated annual survival and fidelity of adult (n = 165) and hatch-year (n = 671) Piping Plovers from 2008 to 2018 and within-season weekly survival of breeding adults (n = 271) from 2011 to 2024. Annual adult survival was 0.771 (95% CI = 0.733–0.804) and hatch-year survival was 0.394 (0.335–0.456). Fidelity to the study area was 0.737 (0.634–0.819) for adults and 0.261 (0.192–0.345) for hatch-years. Within-season apparent weekly survival was higher for Piping Plovers at lakeshore housing developments (0.946 [85% CI = 0.917–0.965]) than sand and gravel mines (0.909 [0.874–0.935]) and transition sites (0.881 [0.834–0.928]). Annual survival of adult and hatch-year birds were comparable to other studies and regions within the Northern Great Plains population, indicating no negative consequence of off-river nesting to survival. Considering that off-river habitats are important for the persistence of Piping Plovers in the lower Platte River system, continued monitoring of survival could help managers evaluate recovery implications under uncertain future habitat availability in the region.

Nebraska↗
USGS2028

Migration ecology and stopover population size of Red Knots Calidris canutus rufa at Mingan Archipelago after exiting the breeding grounds

Populations of migratory birds present unique conservation challenges given the often vast distances separating critical resources throughout the annual cycle. Migration areas close to the breeding grounds represent a link between two key stages of the annual cycle, and understanding migration ecology as birds exit the breeding grounds may be particularly informative for successful conservation. We studied migration phenology and stopover ecology of an endangered subspecies of the Red Knot Calidris canutus rufa at a migration area relatively close to its breeding range. Using mark-recapture/resight data and a Jolly-Seber model for open populations, we described the arrival and departure schedules, stopover duration, and passage population size at the Mingan Archipelago, Quebec, Canada. Red Knots arrived at the study area in two distinct waves of birds separated by approximately 22 days. Nearly 30% of the passage population arrived in the first wave of arrivals during 15–18 July, and approximately 22% arrived in a second wave during 8–11 August. The sex-ratio in the stopover population at the time of the first wave was slightly skewed toward females, whereas the second wave was heavily skewed toward males. Because males remain on the breeding grounds to care for young, this may reflect successful breeding in the year of our study. The estimated stopover duration (population mean) was 11 days (95% credible interval: 10.3–11.7 days), but stopover persistence was variable throughout the season. We estimated a passage population size of 9,450 birds (8,355–10,710), a minimum estimate for reasons related to the duration of our sampling. Mingan Archipelago is thus an important migration area for this endangered subspecies and could be a priority in conservation planning. Our results also emphasize the advantages of mark-recapture/resight approaches for estimating migration phenology and stopover persistence.

Quebec↗
USGS2015

Breeding ecology of Wandering Tattlers Tringa incana: a study from south-central Alaska

Montane-nesting shorebirds are arguably the least studied of the Charadriiformes, owing in part to the remoteness of their breeding areas, low nesting densities, and specialized behaviors. We studied a marked population of the Wandering Tattler Tringa incana, during a three-year period (1997–1999) on nesting grounds in south-central Alaska. Two aspects of our results stand out. First is the previously undescribed preference for tattlers to nest several kilometers removed from pre-nesting feeding areas, mostly in association with both small (kettle) lakes and running water (near small distributaries of major drainages). Second is the apparent use of the study area by cohorts of birds of different breeding status, including (1) local breeders, which defended pre-breeding foraging areas, (2) local non-breeding birds, which remained on the area but were not territorial, and (3) transients that were captured later in the season, but not seen again on the area during the season of capture. We also found that (1) birds tended to nest in clusters despite what appeared to be the ample availability of nesting habitat, (2) they employed an inconspicuous’ nesting strategy whereby neither member of a pair betrayed its presence on the nesting area, and (3) females departed the area during early chick-rearing, leaving males to tend broods.

Alaska↗
USGS2006

Shorebird avoidance of nearshore feeding and roosting areas at night correlates with presence of a nocturnal avian predator

We here report two anecdotes about avian interactions relevant to the interpretation of differences in shorebird habitat use between day and night . Several studies have reported that shorebirds avoid feeding and roosting along nearshore areas at night yet commonly use these sites during daytime. This suggests that nighttime avoidance of nearshore places is a response to increased danger of predation. When mist-netting during autumn 2005 on nearshore intertidal habitats along South Spit, Egegik Bay (Alaska Peninsula), Alaska, we discovered that shorebirds that occurred there in large numbers during daytime low tides and roosted there during daytime high tides (especially Dunlin Calidris alpina, Rock Sandpipers Calidris ptilocnemis, Black-bellied Plover Pluvialis squatarola, and Surfbirds Aphriza virgata), were absent at night . Their avoidance of the area correlated with Short-eared Owls Asio flammeus concurrently hunting over the beach and adjacent intertidal habitats. Spotlighting over nearby expansive intertidal mudflats confirmed that the same suite of species continued to forage or roost nearby at night. To bring the story full circle, the morning following one mist-netting effort we found a Short-eared Owl on the beach that had been killed earlier by a Gyrfalcon Falco rusticolus. In the owl’s stomach were remains of a freshly devoured Dunlin.

Wader Study Group Bulletin↗
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↗