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.
