Trends in nonbreeding shorebirds along the Pacific Americas Flyway

Abstract Population trends for shorebirds that spend the nonbreeding period of their annual cycle along the Pacific Americas Flyway are largely unknown. However, localized studies within the Pacific Flyway and analyses from the Atlantic Flyway suggest many shorebird species may be declining in the Western Hemisphere. Herein, we present the first trends of nonbreeding shorebirds along the Pacific Americas Flyway based on a coordinated survey effort from across a large portion of the Flyway. We used 10 years of survey data collected annually (2012–2013 to 2021–2022) between November and February from 10 countries along the Pacific Coast of the Americas to assess population trends for 22 species. There was a mix of positive and negative trend estimates across species. Overall, 10 of 22 species had a significant negative trend; 7 were significant at the P < 0.05 level and an additional 3 species showed evidence of significant decline at the P < 0.15 significance level. Two species evaluated were significantly increasing at P < 0.05. Of 17 species evaluated with regional models, the directionality of trend estimates by species was broadly consistent between the North Temperate and Neotropical regions of the Flyway. However, for 5 species the directionality of the trends differed between regions. Overall, species with uncertain trends generally had lower numbers of survey events and units included in the analysis because often they were affiliated with habitats with relatively limited sampling. While there was still uncertainty in the trend estimates for some species, we have strong evidence that some species were significantly declining, and at least a couple were increasing during our study period. Our results provide critical information to guide the prioritization of conservation investments and further investigations into the causes of shorebird declines, as well as increases, at regional and flyway scales along the Pacific Americas Flyway.