CONSPECIFIC REPRODUCTIVE SUCCESS AND BREEDING HABITAT SELECTION - IMPLICATIONS FOR THE STUDY OF COLONIALITY

Habitat selection is a crucial process in the life cycle of animals be cause it can affect most components of fitness. It has been proposed t hat some animals cue on the reproductive success of conspecifics to se lect breeding habitats. We tested this hypothesis with demographic and behavioral data from a 17-yr study of the Black-legged Kittiwake (Ris sa tridactyla), a cliff-nesting seabird. As the hypothesis assumes, th e Black-legged Kittiwake nesting environment was patchy, and the relat ive quality of the different patches (i.e., breeding cliffs) varied in time. The average reproductive success of the breeders of a given cli ff was predictable from one year to the next, but this predictability faded after several years. The dynamic nature of cliff quality in the long term is partly explained by the autocorrelation of the prevalence of an ectoparasite that influences reproductive success. As predicted by the performance-based conspecific attraction hypothesis, the repro ductive success of current breeders on a given cliff was predictive of the reproductive success of new recruits on the cliff in the followin g year. Breeders tended to recruit to the previous year's most product ive cliffs and to emigrate from the least productive ones. Consequentl y, the dynamics of breeder numbers on the cliffs were explained by loc al reproductive success on a year-to-year basis. Because, on average, young Black-legged Kittiwakes first breed when 4 yr old, such a relati onship probably results from individual choices based on the assessmen t of previous-year local quality. When breeders changed breeding cliff s between years, they selected cliffs of per capita higher reproductiv e success. Furthermore, after accounting for the potential effects of age and sex as well as between-year variations, the effect of individu al breeding performance on breeding dispersal was strongly influenced by the average reproductive success of other breeders on the same clif f. Individual breeding performance did not appear to influence the pro bability of dispersing for birds breeding on cliffs with high local re productive success, whereas individual breeding performance did have a strong effect on dispersal for birds that bred on cliffs with lower l ocal reproductive success. This suggests that the reproductive success of locally breeding conspecifics may be sufficient to override an ind ividual's own breeding experience when deciding whether to emigrate. T hese results, which are supported by behavioral observations of the ro le of prospecting in recruitment, suggest that both first breeders and adults rely on the reproductive success of conspecifics as ''public i nformation'' to assess their own chances of breeding successfully in a given patch and to make settling decisions. A corollary prediction is that individuals should attempt to breed near successful conspecifics (a form of social attraction) in order to benefit from the same favor able local environmental conditions. Such a performance-based conspeci fic attraction mechanism can thus lead to an aggregative distribution of nests and may have played a role in the evolution of coloniality.