The Pacific coast population of the Western Snowy Plover Anarhynchus nivosus nivosus is vulnerable to the loss of the dune and sandy beach habitats used by this threatened shorebird. Preservation and restoration of coastal nesting habitat is fundamental to recovery of the species and requires a detailed understanding of nest-site habitat preferences. Sandy coastlines are dynamic systems, limiting the timeframe in which habitat measurements reflect the characteristics plovers select when initiating a nest. However, the most relevant timeframe for data collection is also when plovers are most sensitive to disturbance: during the breeding season. We surveyed habitat at plover nest sites and nearest random points during the breeding season and the fall immediately post-breeding to examine nest-site microhabitat selection and to determine whether post-breeding habitat measurements are still representative of breeding season habitat. We found that plovers select nest sites based on overall microhabitat characteristics rather than specific plant species. Across seasons, nest sites were significantly more likely to have adjacent objects (vegetative or inanimate). Nests tended to be located where cover of pioneer stabilizers, a dune plant functional group that includes Beach Bur Sage Ambrosia chamissonis, was ~10%, and where pioneer builders, another group which includes Sea Rocket Cakile maritima, American Dune Grass Leymus mollis, and Beach Saltbush Atriplex leucophylla, were present at less than 5 or 10% cover, depending on the presence and type of the adjacent object. Seasonal differences were minimal, suggesting that fall habitat may still be representative of breeding season habitat. Based on these findings, we make recommendations for approaches that could be applicable across the range of the Pacific coast population and encourage delaying habitat assessments until the breeding season concludes. Our research helps bridge the gap between scientific findings and practical implementation of habitat monitoring and management of the Western Snowy Plover.
In arid and semi-arid regions, interannual variability in rainfall strongly influences wetland hydrology and can critically affect the breeding performance of wader species. Here we study the breeding biology of the Black-winged Stilt during three consecutive seasons (2017–2019) in a peri-urban lagoon complex near Essaouira city on the Atlantic coast of Morocco. At this site, water level is primarily linked to cumulative annual precipitation and disturbances by humans are frequent. Mean pond percent area full was lower in 2018 (59%) than other years (76–79%), reflecting drier conditions in that year. Analysis of individual clutches revealed that most were laid in late April, with an average of 3.25 ± 1.08 SD eggs per nest. The incubation period lasted 24.03 ± 0.91 days. Hatching success over the entire study period was 69.7% of all laid eggs and mean productivity was 2.32 hatched chicks per successful nest. Unsuccessful nesting attempts were mainly attributed to nest and egg destruction due to human disturbance (39%) and weather conditions (20%). The length of the laying period differed significantly between 2017 and 2018 (56 vs. 30 days), although that recorded in 2019 (48 days) was not significantly different from either year. The shorter laying period observed in the dry year of 2018 likely reflects that only higher-quality individuals were able to breed under the less-favorable conditions (low cumulative annual precipitation, lower percent pond area full), which was associated with a reduced availability of suitable nesting sites. Overall, our results highlight the combined influence of rainfall-driven hydrological variability and human disturbance on breeding performance, emphasizing the vulnerability of peri-urban wader breeding populations in temporary wetlands.
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.
Common Redshanks Tringa totanus are shorebirds that breed in Eurasia and have a non-breeding range across the south of Eurasia, Africa and Australia. However, there is limited information on their migration behaviour in Central and Eastern Asia. This study documented nine Common Redshanks caught during the non-breeding season in southern Bangladesh and tracked on migration to their breeding grounds in Qinghai (north-west China) and Siberia over the Himalayan mountain range. These data were compared with Common Redshanks caught in Singapore during the non-breeding season, which also undertook the trans-Himalayan journey. We aimed to identify the unique features of Bangladesh-wintering individuals, by comparing the migration routes and breeding grounds of these two groups of trans-Himalayan migrants. We expected overlap between these two groups in general breeding areas and passage routes through the mountains, as both groups are likely to use the least energetically costly migration paths. Our tracking data revealed that the Bangladesh non-breeding individuals had a narrow migration corridor (4.72 ± 1.19 degrees of longitude) compared to individuals from Singapore (12.97 ± 3.45), and a shorter mean migration distance than migrants from Singapore. There was no clear overlap of breeding range even among individuals breeding in the Qinghai-Tibetan Plateau, despite the same path through the mountains being taken by both groups. Three individuals from Bangladesh bred outside the previously known breeding range; two in Qinghai, and one in Khakassia, Russia. This study further strengthens the need for more research and conservation of birds and wetlands along the Central Asian Flyway, including the understudied Qinghai-Tibetan Plateau region.
We used geolocators recording ambient light, conductivity and wet/dry conditions to study the migration of Little Ringed Plovers Thinornis dubius breeding in the Netherlands. Little Ringed Plovers breeding in western Europe mostly migrate in the autumn towards the inner Niger delta in western Africa, mainly using stopover sites around the Mediterranean Sea. Conductivity data indicate that these autumn stopover sites are saline or brackish habitats, suggesting that saline coastal marshes or manmade saline aquatic habitats (saltworks) are important stopover habitats for Little Ringed Plovers. The timing of the spring migration coincides with the spring equinox (preventing accurate geolocator fixes); therefore we could not locate stopover sites in spring. However, we were able to use the conductivity data to infer the timing of the spring stopover sites and migration. We found that migrating Little Ringed Plovers spent 15% (females) or 17% (males) of their time in saline aquatic habitats.
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.
Shorebird populations in North America are experiencing worrisome rates of decline, with 93% of shorebird species showing negative trends in abundance during 1980–2019. These declines are attributed mainly to habitat loss, decreases in food availability (e.g. American Horseshoe Crab Limulus polyphemus eggs), and climate change. Human disturbance at migratory stopover sites may exacerbate the effects of these major threats by affecting rates of mass gain and patterns of space use by shorebirds. We recorded the abundance and behavior of migratory shorebirds at critical barrier island staging sites surrounding Little Egg Inlet on the New Jersey Atlantic Coast, and the impacts of human activities on shorebird abundance and distribution in the study area. We found that increased human activity was associated with a significant decrease in shorebird abundance and that humans and shorebirds preferred to use the same areas of the beach. Certain human activities tended to cause more disturbance than others, mainly motorized watersports and people walking, suggesting that shorebirds find some human behaviors more immediately threatening than others. We recorded a distinct second peak, in mid-October, in Red Knot Calidris canutus abundance. Based on our results, we recommend keeping staging sites in our study area seasonally closed to the public from April 1 through November 1 (instead of September 1) when the bulk of shorebird migration has passed.
