Actuarial and reproductive senescence in a long-lived seabird: preliminary evidence.

The evolutionary theory of aging predicts that pelagic seabirds, which have low extrinsic mortality, should show exceptional longevity. These taxa appear to show the lowest rates of actuarial senescence among birds yet display declining reproductive performance at advanced ages. We have studied survival and reproduction of Nazca boobies (Sula granti) in the remote Galápagos Islands since 1984. We found a slight but detectable increase in mortality rate in the oldest (> or =19 yrs) cohort, indicating minimal actuarial senescence. The probability of successful reproduction (eggs or fledglings) declined from mid-life to the age of the oldest cohort. We are currently investigating the causal relationship between physical (foraging) performance, components of reproductive success, and longevity at our pristine study site.