Large-scale sampling of potential breeding sites in male ruffs.

The traditional narrative of the life cycle of migratory birds is that individuals perform long-distance movements between a breeding and a wintering site, but are largely resident at those sites. Although this pattern may apply to socially monogamous species with biparental care, in polygamous systems, the sex that only provides gametes may benefit from continuing to move and sample several potential breeding sites during a single breeding season. Such behaviour would blur the distinction between migration and breeding. We used satellite telemetry to study movements during the breeding season of males of the ruff , a lekking wader with a polygynous mating system and female-only parental care. Ruffs have a unique life-history, with three distinct genetically determined male mating strategies: aggressive 'independents', submissive 'satellites', and female-mimicking 'faeders'. Within the breeding season, ruff males visited up to 23 sites (median: 11) and travelled up to 9029 km (median: 4435 km) covering a considerable part of their known breeding range. All three male morphs displayed breeding site sampling, indicating that they might gain similar benefits from this behaviour. Our findings suggest that large-scale breeding range sampling may be a common feature of migratory species with female-only care and strong male-male competition.