Second Breeding Attempts of Sandwich Terns in a Different Colony: Facilitated by Breeding Asynchrony between Colonies?

Seabirds have long lives, reproduce slowly and usually do not attempt to relay within the same breeding season after nest failure. In Sandwich Terns Thalasseus sandvicensis, renesting has never been documented despite the large number of studies on their breeding ecology and recorded prospecting behaviour after nest failure. In 2020, we observed how three GPS-tagged Sandwich Terns moved 115 km after nest failure for a second breeding attempt. One of these birds hatched a chick from the second clutch successfully. We hypothesize that synchronous breeding usually prevents Sandwich Terns from trying again after nest failure and that the relays observed in 2020 were facilitated by the unusual situation of a successful breeding colony that started three weeks later than all other colonies in the Netherlands.