Variation in Migration Distance Does not Affect Arrival Date in the Subsequent Breeding Season of Dutch Barn Swallows Hirundo rustica

Long distance migrants like Barn Swallows have to operate within narrow time-frames to fit post-breeding migration, wintering (including wing moult) and pre-breeding migration into their annual cycle. As a short-lived passerine, Barn Swallows have evolved towards maximising annual reproduction in order to increase fitness. To achieve this, a timely arrival at the breeding location is an important precondition to realise the necessary two breeding attempts. Ringing recoveries indicate that Dutch Barn Swallows winter across large parts of Central and Southern Africa. But ringing recovery data have limitations to analyse spatial-temporal occurrence throughout the annual cycle. We used geolocators to describe spatial and temporal aspects during migration and wintering of 20 Barn Swallows, breeding in The Netherlands (2011–2013). The results of our geolocator research and the ringing research showed broadly similar northern and southern limits of the wintering areas: from Ghana to South Africa. However, the centres of gravity of both methods differed completely. Geolocator-based wintering areas were mainly in the Congo Basin, from which no ringing recoveries are known. We evaluated correlations between timing, duration and distance travelled for the different stages of the annual cycle. The result that a longer post-breeding migration distance did not lead to a later arrival at the breeding location in the subsequent year, was contrary to our expectations. Despite methodological improvements made between research years, the results of this study came with a ‘cost’ for the birds involved. In both research years, the return rates of both geolocator groups were 17 percent points lower than their respective control groups.