No abstract

No abstract

No abstract

246 feral cats were shot on Macquarie Island, Australia, between Dec. 1976 and Feb. 1981. The sex ratio ( males : females ) was 1:0.8. The percentages of animals with tabby, orange and black coats were 74, 26 and 2 resp. [sic]. Of the 64 orange cats, 56 were males . The breeding season was Oct.-Mar., with a peak in Nov.-Dec. The number of embryos in the 14 pregnant females averaged 4.7 (range = 1-9). The size of the 23 litters that were observed averaged 3 (range = 1-8). Kitten survival to 6 months of age was estimated to be <43%.

Summary1. 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 signi®cant dierence), 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 ospring, even when years of absence were allowed for. 4. The frequency of attendance, laying and successful rearing of progeny to¯ed-ging 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-os between the eort 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.