Peter Olsson

The repair jobs that birds have to do to maintain high quality plumage take energy and time, so should be under intense selection. Recently, we have shown that secondary moult in the Eurasian Golden Plover Pluvialis apricaria is incomplete, irregular and asymmetric between wings, and argued that this reflected their ‘relaxed’ migratory habits. On the basis of this hypothesis, we predict that relatives of this species that have to make long flights between breeding areas and winter quarters would invest more in the moult of secondaries. To test this we collected data on moult patterns in two populations of Pacific Golden Plovers Pluvialis fulva (Siberia and Alaska), on American Golden Plovers Pluvialis dominica (Alaska) and Grey Plovers Pluvialis squatarola. Data were from the breeding, staging (Mongolia and Indiana) and wintering (Uruguay) areas. We found patterns consistent with our prediction: Pacific Golden Plovers from Siberia, and Grey Plovers have a similar moulting pattern to Eurasian Golden Plovers. Although both go to remote winter quarters, they migrate mainly over land, probably making short or moderate flights, as they are able to stage frequently. In contrast, the Alaskan populations of Pacific Golden Plovers and American Golden Plovers tend to renew all their secondaries from their second wing moult onwards. In line with their moult patterns, these two populations are known to make very long non-stop flights between breeding and winter areas. We argue that irregular moult and the partial renewal of secondaries is a primitive character in all four species. The full replacement of secondaries in the Pacific Golden Plovers and American Golden Plovers from Alaska may be considered as an adaptation for very long demanding flights. Regular moult patterns of secondaries, as found in many other shorebirds, could be a further refinement of this adaptation.