Intermittent breeding in the short-tailed shearwater Puffinus tenuirostris

1. At one colony of short-tailed shearwaters in Bass Strait, Australia, all birds breeding have been recorded individually each year for over 50 years. Among individuals known to be alive and to have bred before, 14% of each sex were not present at their breeding colony, on average, in any one year. 2. A further 15% of males and 13% of females (a significant difference), known to have bred before, were present but not associated with an egg in any one year. 3. Intermittent breeding was associated with pair bond breakdown and with a reduced ability to raise offspring, even when years of absence were allowed for. 4. The frequency of attendance, laying and successful rearing of progeny to fledging increased with age in the early years of breeding. However, this was followed by a decrease, except in the case of laying frequency, which continued to increase throughout life. 5. Our analysis indicated that intermittent breeding in short-tailed shearwaters did not result from individuals implementing trade-offs between the effort required for breeding success and their breeding life span. Rather, we suggest that individuals of higher quality are able to breed more frequently than others without any compensatory reduction in either their annual breeding success or their overall breeding life span.