Global population estimate and conservation gap analysis for the Nordmann's Greenshank (Tringa guttifer)

Nordmann's Greenshank (Tringa guttifer) is a globally endangered species that has received little research attention. It is threatened by rapid habitat loss, an incomplete network of protected sites, and lack of long-term data on population dynamics. Citizen science data can be combined with survey data to support population estimation and conservation gap analysis. From 2020 to 2021, Nordmann's Greenshank was surveyed in Tiaozini, Xiaoyangkou, and Dongling on the southern coast of Jiangsu Province, China, and the global population of the species was re-evaluated using the data obtained. We integrated citizen science data from eBird and the China Bird Report from 2000 to 2020 with the survey results to identify important habitats harboring over 1% of its total population, and compared this data with existing protected areas to identify gaps in its global conservation. Our survey found that Tiaozini supported at least 1194 individuals. Consequently, its global population was re-estimated to be 1500-2000. Moreover, 45 important habitats were identified based on citizen data and survey results. Although 44.4% and 50.0% of the priority sites in the world and China, respectively, are located outside protected areas, the Conservation Effectiveness Index (C) is 68.4% and 71.1%, respectively, showing that the current coverage of protected areas for this part of its range is reasonable. This study presents the most complete and recent population data to date. Tiaozini is the most important migration stopover site for Nordmann's Greenshanks. The species is under threat in terms of breeding, wintering, and stopover sites. Therefore, we suggest improving monitoring, establishing new protected sites to complete the habitat protection network, and improving the effectiveness of existing habitat protection strategies, including further developing high tide roosting sites.