ARDEA 111(2), 2023 558 Renesting after nest failure leads to an increased invest- ment in the current season, which might jeopardize breeding success and adult survival in future years (e.g. Stearns 1992). Renesting is regularly recorded among birds, although later timing is usually associated with lower reproductive success (e.g. Price et al. 1988, Arnold et al. 2004, Nisbet 2019). In some species, however, renesting led to similar or even increased breeding success (e.g. Becker & Zhang 2011, Hipfner & Nettleship 2001). Renesting is also associated with a lower body condition of fledglings and thus post- fledging survival rates (e.g. Jakubas & Wojczulanis- Jakubas 2013, Swift et al. 2020), although also here exceptions have been reported (Hipfner et al. 2004). Whether renesting leads to increased lifetime reproduc- tive success depends largely on the number of repro- ductive years in an individuals’ lifetime, with renesting being profitable in short-lived species but not in long- lived species (Stearns 1992, Golet et al. 1998). Indeed, renesting is rarely observed in most species of seabirds, which are generally long-lived and slowly reproducing (K-selected) species (Weimerskirch 2001). Among seabird families, renesting is less rare in the smaller gulls Laridae and terns Sternidae (e.g. Nicholls 1974, Brown & Morris, 1996, Wendeln et al. 2000). Nevertheless, renesting has never been documented in Sandwich Terns Thalasseus sandvicensis, a species breeding in a few but large colonies along European coasts. This is surprising, given that intensive colour- ring reading has shown extensive prospecting behav- iour prior (Fijn unpubl. data), during (Kralj et al. 2023) and post breeding (Fijn et al. 2014). The prospecting during and post breeding may be behaviour that is aimed at or at least facilitates renesting in another colony (e.g. Ward 2005, Pakanen et al. 2014, Martinovic ´ et al. 2019). Although renesting of failed breeders has been suspected to occur in Sandwich Terns (Veen 1977, W. Courtens and E. Stienen pers. comm.), no proof has been found. In this paper, we document renesting of three indi- vidual Sandwich Terns that were tracked using GPS- loggers. In addition to the life history-theory arguments of why renesting can be unfavourable in a long-lived species such as the Sandwich Tern, we postulate the hypothesis that Sandwich Terns usually do not renest after nest failure because of strong selection for synchronous breeding phenology within a colony and the lack of sufficient variation in breeding phenology among nearby colonies. We show that an incident of asynchrony in breeding phenology between colonies Second breeding attempts of Sandwich Terns in a different colony: facilitated by breeding asynchrony between colonies? Ruben C. Fijn 1,* & Rob S.A. van Bemmelen 1 Fijn R.C. & van Bemmelen R.S.A. 2023. Second breeding attempts of Sandwich Terns in a different colony: facilitated by breeding asynchrony between colonies? Ardea 111: 558–563. doi:10.5253/arde.2023.a2 Seabirds have long lives, reproduce slowly and usually do not attempt to relay within the same breeding season after nest failure. In Sandwich Terns Thalas- seus sandvicensis, renesting has never been documented despite the large number of studies on their breeding ecology and recorded prospecting behav- iour 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 hypothe- size 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. Key words: Thalasseus sandvicensis, relays, coastal, breeding behaviour, prospecting 1 Waardenburg Ecology, Varkensmarkt 9, 4101 CK, Culemborg, The Netherlands; *corresponding author (r.fijn@waardenburg.eco)