How birds learn to navigate over long distances is something that remains poorly understood, but newly published research has revealed the surprising decisions made by some Manx Shearwaters attempting to navigate back to breeding grounds after being deliberately displaced by scientists.
A total of 13 shearwaters were displaced from Copeland Island, Co Down, being released by researchers in north-west Co Mayo, a direct-line distance of some 294 km away, in order to monitor their movements. Twelve of these birds produced full GPS tracks for their journeys having returned to Copeland, where all shearwaters were recaptured between two and nine days after release.
Eleven of the 12 immediately began to re-orientate north-eastwards back towards Copeland on release, following the north Mayo coast east towards the Bay of Sligo. On reaching the Bay, eight shearwaters continued back to Copeland by following the coast around the north of Ireland. Three, however, reversed their initial movement from the release site and followed the coast around the island of Ireland in the opposite (southern) direction, travelling 910 km further than was necessary.
The homing abilities of Manx Shearwaters were tested in the new research (Matthew Barfield).
The results demonstrate that some Manx Shearwaters are seemingly unaware of the scale of the obstacle posed by a large landmass, even when this is a prominent feature of their regular foraging environment, calling into question their cognitive processes. For example, one hypothesis is that Manx Shearwaters 'collect' locational information the outward leg of feeding journeys, which helps them to navigate home on the return journey.
However, as the researchers state, the abilities of every bird to eventually navigate back to Copeland – even if for some individuals it meant a much longer journey than was necessary – highlights the species' potential to adapt to a situation and come up with a 'plan B' if required.
Reference
Padget, O, Gillies, N, Syposz, M, Lockley, E & Guilford, T. 2022. Shearwaters sometimes take long homing detours when denied natural outward journey information. Biology Letters, DOI: https://doi.org/10.1098/rsbl.2021.0503
