Migration strategy, site fidelity and population size of the globally threatened Sociable Lapwing Vanellus gregarius

Abstract

Population declines of the critically endangered Sociable Lapwing are probably due to high mortality along its migration routes or on its wintering grounds, both of which are very poorly known. We therefore undertook a long-term study of the species’ movements using satellite tagging, colour-ringing, targeted field surveys and a database of historical and recent sightings. We identified two migration flyways from the breeding grounds in Kazakhstan; a longer western route (c. 5200 km) west through southern Russia, then south through the Caucasus to wintering areas in Saudi Arabia and eastern Sudan, and a shorter eastern route (c. 2800 km) south through Turkmenistan and Uzbekistan to wintering areas in Pakistan and north-western India. The migration strategy is characterised by infrequent long-distance movements followed by often lengthy stopovers in a small number of staging areas that are used consistently across years, and by high individual and low between-individual consistency in spatial and temporal patterns of movement. At least four main autumn stopover areas and one additional spring stopover area were identified along the western route, but only one autumn and one spring staging area along the eastern route. There was no relationship between latitude or longitude of breeding and the migration route used, and the same breeding colonies could contain breeding adults and produce chicks of both flyway populations, suggesting that no clear migratory divide exists within the breeding range. Sociable Lapwings spend around a third of the year on their breeding grounds, a third on their wintering grounds and a third moving between them. Birds were highly faithful to passage and wintering sites, but showed low fidelity to breeding sites. Stopover areas and wintering sites are usually located at the interface of dry steppe-like or desert habitats and agriculture, particularly irrigated cropland along rivers. This species selects agricultural habitats throughout its entire life cycle, and its heavy reliance on some of the world’s most anciently cultivated regions suggests that this synanthropic relationship may have evolved over millennia. The recent emergence of irrigated agriculture in the deserts of Arabia allows birds using the western route to winter far north of their previous wintering range and maybe to spread into new wintering areas along the coasts of the Arabian Gulf. The concentration of large numbers of birds at a small number of traditional stopover areas offers the opportunity to quantify the global population size, which we estimate at around 24,000 individuals (95% CL 13,700–55,560). However, it also makes the species particularly vulnerable to hunting and small-scale habitat change. Illegal hunting along the western flyway is identified as the most likely driver of the species’ decline.