Breeding chronology and productivity of Black-legged Kittiwakes Rissa tridacytla at Bluff, Alaska, 1975–2008: Associations with regional environmental indices and distant colonies

Abstract

Breeding chronology and productivity of Black-legged Kittiwakes Rissa tridactyla at Bluff, Alaska, were documented nearly annually during 1975–2008. Nest numbers and productivity were highest, and hatching was earliest, when spring conditions were warmest. Comparing Bluff with five other colonies in the Bering and Chukchi Seas with long-term data sets, breeding began relatively early along the Alaskan coast compared with the Pribilof Islands (St. Paul and St. George), and progressively much earlier relative to sea ice retreat at more northern coastal colonies. Average annual productivity was significantly higher at Bluff and Cape Lisburne than at Cape Peirce, owing perhaps to higher intraspecific competition for food or higher predation on eggs and chicks at Cape Peirce. Breeding chronology was positively correlated at Bluff and Cape Peirce, and productivity was positively correlated between Bluff and both capes Peirce and Lisburne; these colonies are in the flow field of Alaskan Coastal Water. Both breeding chronology and productivity on St. Paul Island in the Middle Shelf Domain were strongly and independently correlated with timing and productivity not only at nearby St. George Island but also at Bluff, possibly reflecting stronger couplings to continental-shelf food webs on St. Paul than St. George. Both breeding chronology and productivity were significantly correlated between Cape Peirce and both St. Paul and St. George islands, suggesting commonalities across water masses that have very different patterns and processes of seasonal food web development. Productivity on St. George Island was highest in years when winter sea ice concentration was highest, in apparent contrast to Bluff; however, productivity at both St. George and Bluff was higher in years of earlier ice retreat. Positive correlations in both timing and productivity among colonies in disparate oceanic regimes could be due to similarities in pre-breeding condition of adults if they winter or stage in early spring in the same or similar areas.