Colony and Population Dynamics of Black-Legged Kittiwakes in a Heterogeneous Environment

Abstract

Abstract Black-legged Kittiwakes (Rissa tridactyla) nest at 25 distinct colonies located throughout Prince William Sound that range in size from <20 to >7,000 pairs. Dramatic changes have occurred in the distribution of breeding birds among those colonies during the past few decades (1972–1997). Reproductive success data collected since 1985 confirm that individual colonies are habitat patches of varying quality in space and time. Even with such variation, predictability of habitat quality did occur in short- and long-term (≥3 year) intervals as indicated by significant (P < 0.05) relationships between current (t) and previous year's (t−1, t−2, etc.) reproductive success. Those circumstances provided suitable conditions for testing hypotheses concerning dispersal and recruitment strategies of a long-lived species. Breeding birds responded to both short- and long-term cues and, in general, recruited to the most successful colonies. An apparently lower dispersal propensity and the importance of long-term cues was in contrast to a similar study of kittiwake colonies in France (Danchin et al. 1998). Differences between these studies may be attributed to primary factors controlling habitat quality in Prince William Sound operating in the long-term versus the short-term and the magnitude of scale. Colonies in our study covered a much larger geographic area and therefore, factors such as foraging-site faithfulness, mate retention, and natal philopatry may also have influenced dispersal decisions. Nonetheless, recruitment of kittiwakes in Prince William Sound supported the performance-based conspecific attraction hypothesis, which, in turn, led to an ideal free distribution of breeding birds. Those short-term mechanisms for dispersal and recruitment manifested in a long-term redistribution of nesting kittiwakes from poor breeding conditions in southern Prince William Sound to favorable conditions in northern Prince William Sound. Favorable conditions in northern Prince William Sound were apparently supported by stable or increasing populations of juvenile herring. In contrast, reproductive failures and population declines in southern Prince William Sound were concordant with colonies in the Gulf of Alaska where diets were similar, consisting of primarily capelin (Mallotus villosus) and Pacific sand lance (Ammodytes hexapterus). Those trends corresponded with the influence of Gulf of Alaska waters in southern Prince William Sound and may have been associated with a reported decline in the abundance of key forage species related to a late 1970s regime shift in the Gulf of Alaska.