A study of some factors influencing breeding of the kittiwake gull Rissa tridactyla (L.)

Abstract

The kittiwake is restricted to breeding within colonies. The effect of nesting density on the time of breeding and on breeding success was investigated, at colonies in Northeast England. Evidence exists that the female kittiwake requires stimulation from the mate, and from surrounding pairs, before breeding. The positive effect of nesting density, that is, social stimulation, is mediated through its effect on laying date, resulting in larger clutches of birds breeding at high density. There is a seasonal decline in clutch size. Nesting density has a negative effect on the number of young produced from eggs that hatch, which may be due to the negative action of accepted density dependent factors. The effect of social stimulation is not restricted to any one year, but is carried forward to the next and subsequent seasons. Birds which breed at high density return to the colony earlier in the following year, and at a more advanced stage of the pre-nuptial moult. Behavioural studies during the pre-egg laying phase have indicated that the colony, unless very small, never functions as a whole, but as a series of interacting and interlinking groups. The effect of nesting density is not one of mean colony density: the position of the nest within a colony is of importance. Although it is accepted that there are differences between recruits to high and low density areas, it is proposed that many of the subsequent differences are mediated through the effect of social stimulation on hormone secretion.