REPRODUCTIVE SUCCESS OF SHORT-TAILED SHEARWATERS PUFFINUS-TENUIROSTRIS IN RELATION TO THEIR AGE AND BREEDING EXPERIENCE

The proportion of eggs 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 to 0.55-0.65 in the most experienced birds. 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. Older 1st-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 1st breeding. Individuals that lived for longer had a higher reproductive success, on average, than shorter-lived birds, especially early in their reproductive careers. -from Authors