Shearwaters make efficient navigational decisions, even at very fine scales

Seabirds are superb long-distance navigators, navigating across oceans with remarkable accuracy. Whilst the mechanisms facilitating these movements are increasingly understood, it is unclear how accurately seabirds determine their position on finer scales. Here, we investigated local navigation in the Manx shearwater (Puffinus puffinus) by displacing GPS-tracked individuals to sites around their colony island. Because shearwaters normally avoid flying over land, these release sites present a choice of two over-sea island circumnavigation routes that differ in distance. We found that birds preferentially adopted the shorter round-island route, demonstrating that shearwaters are capable of learning route efficiencies even when differences in payoff are very slight in comparison to the distances they routinely travel. We discuss the learning mechanisms that may underpin this navigational efficiency; including how birds might distinguish between routes where the absolute difference in payoff is minimal, but the relative payoff is large.