Abstract
Non-breeding movement strategies of migratory birds may be expected to be flexibly adjusted to the distribution and quality of habitat, but only few studies compare movement strategies between populations using distinct migration routes and wintering areas. In thisour study, individual movement strategies of Rred-necked pPhalaropes Phalaropus lobatus, a long-distance migratory wader using saline waters in the non-breeding period, were studied using light-level geolocators. Results revealed the existence of two populations with distinct migration routes and wintering areas: one breeding in the north-eastern North Atlantic and migrating ca. 10,000 km oversea to the tropical eastern Pacific Ocean and the other breeding in Fennoscandia and Russia migrating ca. 6,000 km – largely over land – to the Arabian Sea (Indian Ocean). In line with our expectations, the transoceanic migration between the North Atlantic and the Pacific was associated with proportionately longer wings, a more even spread of stopovers in autumn and a higher migration speed in spring compared to the migration between Fennoscandian-Russian breeding grounds and the Arabian Sea. In the wintering period, birds wintering in the Pacific were stationaryresided in roughly a singlethe same area, whereas individuals wintering in the Arabian Sea showed individually consistent movementsd extensively between different areas, reflecting differences in spatio-temporal variation in primary productivity between the two wintering areas. Our study is unique in showing how habitat distribution shapes movement strategies over the entire non-breeding period within a species.
Highlights
IntroductionDuring the non-breeding season, migratory birds cover long distances to track spatio-temporal peaks in resource abundance and avoid unfavorable conditions over large spatial scales (Newton, 2010; Thorup et al, 2017)
Animal movements are strongly linked to habitat and resource availability
Our study demonstrates the existence of two distinct populations of red-necked phalaropes within the Western Palearctic: one that breeds in Fennoscandia and Russia and winters in the Arabian Sea (Indian Ocean) and another that breeds on islands in the north-eastern North Atlantic (Greenland, Iceland and Scotland) and winters in the Pacific
Summary
During the non-breeding season, migratory birds cover long distances to track spatio-temporal peaks in resource abundance and avoid unfavorable conditions over large spatial scales (Newton, 2010; Thorup et al, 2017). Movement strategies are expected to be flexibly adjusted to habitat availability and quality within the boundaries set by, for example, maximum fattening rates and fuel loads, resulting in different strategies among individuals or populations using different migration routes and wintering areas. Surprisingly similar migration strategies have been observed in other species, despite geographically distinct migration routes (Fraser et al, 2013; Trierweiler et al, 2014). The extent to which species flexibly adjust large-scale movement strategies to habitat remains poorly understood
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