Transatlantic migration by post-breeding puffins: a strategy to exploit a temporarily abundant food resource?

The distribution of Atlantic puffins( Fratercula arctica) from Skellig Michael, south-west Ireland, was investigated using geolocationloggers between the 2010 and 2011 breedingseasons. All tracked birds travelled rapidly west into the North Atlantic at the end of the breedingseason in August, with the majority undertaking transatlantic trips from Ireland to the Newfoundland-Labrador shelf. The furthest distance from the colony reached by each bird was not influenced by body mass or sex and was achieved in approximately 20 days. By October, all birds had moved back to the mid Atlantic where they remained resident until returning to the breedingcolony. The most parsimonious explanation for the rapid, directed long-distance migration is that birds exploit the seasonally high abundance of prey [e.g., fish species such as capelin( Mallotusvillosus) and sandlance ( Ammodytesspp.)] off the Canadian coast, which is also utilised by large populations of North American seabirdsat this time. Once the availability of this short-term prey resource has diminished, the tracked puffinsmoved back towards the north-east Atlantic. A relationship between relative abundance of puffinsand zooplankton was found in all winter months, but after correcting for spatial autocorrelation, was only significant in November and January. Nevertheless, these results suggest a potential switch in diet from mainly fish during the breedingand early post- breedingperiods to zooplankton over the remaining winter period. This study suggests that puffinsfrom south-west Ireland have a long-distance migration strategy that is rare in breeding puffinsfrom the UK and identifies a key non- breedingdestination for puffinsfrom Ireland. This has implications for the susceptibility of different breedingpopulations to the effects of possible climatic or oceanographic change.