Reproductive Success of Short-Tailed Shearwaters Puffinus tenuirostris in Relation to Their Age and Breeding Experience

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Abstract
(1) The proportion of eggs laid by short-tailed shearwaters Puffinus tenuirostris (Temminck) that produced free-flying young increased with increasing breeding experience from an initial 0.4-0.45 to a maximum of 0.75-0.8, before falling of 0.55-0.65 in the most experienced birds. (2) Overall, 10-11% of breeding shearwaters were absent, and 15-18% were present but not recorded with an egg, in any year. Both absentee and non-laying rates declined with increasing age. (3) Older first-breeding birds had a higher initial reproductive success than those starting younger. Thereafter, there were no consistent differences in reproductive rates related to age of first breeding. (4) Individuals that lived for longer had a higher reproductive success, on average, than shorter-lived birds, especially early in their reproductive careers. (5) The reproductive performance of short-tailed shearwaters appeared to be influenced by age, cumulative breeding experience, residual reproductive value and differential survival of successful breeders.