Interference of copulation in a colony of marked black-legged kittiwakes

Abstract

During behavioural observations (1979–1981) at a colony of black-legged kittiwakes (Rissa tridactyla) nesting on the window ledges of a warehouse, some breeding and nonbreeding males interfered with the copulations of conspecific colony members. The proportion of copulations interfered with varied from 15 to 27% depending upon year. Four types of interference were identified. Interference stopped 51% of copulations and temporarily halted another 37%. Some interfering birds were individually identified by colour bands or other unique features. Identified males seen to interfere at least once did not differ significantly with respect to breeding experience from those never seen to interfere, but the former group had paired with their mates for significantly fewer years than the latter. The majority of interferences by breeding males were performed during the 2-week period before their mates laid eggs: a period coincident with peak rates of copulation for these pairs. The results are used in an evaluation of hypotheses for the adaptive function of interference behaviour.