Influence of environmental variability on breeding effort in a long-lived seabird, the yellow-nosed albatross

The provisioning parameters, breeding success, adult mass, and survival of yellow-nosed albatrosses were studied over 7 successive years at Amsterdam Island, southern Indian Ocean. We examined the ability of this long-lived seabird to adjust its breeding effort under different environmental conditions and the fitness consequences in terms of survival and quality of offspring produced. Provisioning rate and adult mass varied extensively between years, and the lowest and highest values were associated with sea surface temperature anomalies. When waters around the island were colder, adults were in good condition and brought large meals at short intervals, whereas warmer waters resulted in lower provisioning rates, lower adult mass, and lighter chicks at fledging. Adult survival and fledging success were not affected by sea surface temperature anomalies. Yellow-nosed albatrosses appear to be unable to adjust their breeding effort every season, and their differential breeding investment probably primarily reflects different levels of food availability. Yellow-nosed albatrosses are able to regulate their provisioning behavior according to the nutritional status of their chick only when conditions are favorable. Birds appear to invest primarily in their own future maintenance rather than in provisioning. They have a wide safety margin in body mass that limits mortality risks during good years as well as during poor years. However, during unfavorable seasons adults continue to provision chicks that have a poor prospect of survival to breeding, without additional survival costs for the parents. Favorable seasons therefore have a high value in terms of fitness because of the high quality of the chick produced. We suggest that understanding how long-lived animals optimize their provisioning behavior and lifetime reproduction can only be achieved through studies encompassing several contrasted seasons.

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