Mate retention in the kittiwake,Rissa tridactyla, and the significance of nest site tenacity

Abstract

Data on mate retention and nest site tenacity of kittiwakes at North Shields (1954-1990) were analysed and the effect of a forced change of breeding site on mate retention (1991-1993) examined. Although kittiwakes in 1991 were prevented from returning to nest sites of the previous breeding season, 73% of females and 60% of males that bred elsewhere retained their mates of the previous breeding season. Of kittiwakes that moved to other colonies in 1992, 42% of breeding females and 30% of males retained their mates of the previous breeding season. Over the period 1954-1990, 92% of females and 80% of males that used the same nest sites in the following year retained their mates but 100 pairs that changed nest sites still re-formed the pair bond of the previous breeding season. A model predicted that the probability of retaining the same mate by chance within the warehouse colony should decrease progressively with distance moved from the previous nest site. Mate retention decreased sharply if a bird moved 0·3m to a nest site immediately adjacent to the previous site but, in contrast to the model, did not show a further significant decrease with increasing distance. In the 1991-1993 study, some birds that changed nest sites and moved to a different colony still retained their mates. Therefore, the annual re-forming of the same pair did not result from nest site tenacity as birds were prevented from returning to former nest sites. This implies that birds recognize each other as individuals and possibly move as a pair. Such behaviour has important implications for lifetime reproductive success, as birds that retain their mates from the previous breeding season typically fledge more young than birds that change mates.