This paper presents, as well as some earlier data, the results of a study of the burrowing petrels of the Crozet Islands (South Indian Ocean) made during the East Island expedition of September 1981 to February 1982. The 16 petrels are discussed and analysed in the following taxonomic groups: 4 gadfly petrels, 5 prions, 2 Procellaria petrels, 3 storm petrels and 2 diving petrels. For each group, biometric data and the breeding biology of each species are given. The timing of events (first return to land, laying, hatching, fledging), nest reoccupation, incubation schedule, chick growth and chick-feeding pattern were the main study topics. Abundance cycles during pairing, temporary egg desertions, nest selection, comparison with other localities and particularly ecological segregation of the petrels are discussed.
Experiments were undertaken to identify the animals responsible for attacks on nests of Greenfinches (Carduelis chloris) on a mixed farm in Hawke’s Bay. Nests encased in wiremesh, which excluded all potential predators except mice, suffered no egg losses. Tracking papers placed on wooden poles leading to nests were marked by rats twice. Two ship rats (Rattus rattus) were killed at nests with eggs injected with strychnine.
Mustelids destroyed one clutch of eggs and were probably responsible for most of the predations on young. The experiments did not test whether Harriers (Circus approximans) or other birds were involved.
We studied Pycroft’s Petrel, Pterodroma pycrofti, at a breeding colony in the Hen and Chickens Islands, New Zealand, during the prebreeding and breeding seasons of 1982/83. Breeding birds attended their burrows singly and in pairs, often for several days at a time, from at least 38 days before laying, and up to 19 days before laying.
No parents were in their burrows during the fortnight before laying, except a day or so before laying. In October/November the weights of breeders arriving at their burrows averaged about 150 g, but females arriving to lay weighed on average about 188 g, and males arriving to begin their first incubation stint averaged about 190 g – about 25% more than in October/November. The egg averaged 32 g. Daily weight loss over consecutive days in the burrow averaged 3.5-5 g/day, 2-3g of body weight. Laying took place from the second week in November to the end of the first week in December. Egg dimensions are given. Incubation lasted about 45 days and the fledging period was 77-84 days. Weights of fledglings ranged 156-188 g. From small samples, hatching success was 72% and fledging success 50%. Losses were caused by infertility, desertion and breakage resulting from fighting, probably with tuataras. One male failed breeder was at its burrow six weeks after its egg was broken. Non-breeders are defined as adults not known to breed in the current breeding season but may include some failed breeders. Some occurred in burrows in each observation period, and one was recorded throughout the study period, but more were at the colony in January than earlier. Non-breeders and breeders did not differ significantly in weight in October/November, but non-breeders did not usually achieve
the higher weights of breeders arriving to lay or incubate. Weight loss of non-breeders in burrows was similar to that of breeders. The state of the brood patch, egg formation and the history of previously ringed birds are briefly discussed.
An annotated list of the 52 species of bird seen on and around the Noises Islands in Hauraki Gulf is presented, incorporating information from unpublished field notes from the 1930s onwards and the authors’ own observations, which began in 1977. Eight of the 20 species of seabird and 13 of the 32 species of land bird breed at the islands. The only breeding species of native forest bird are Grey Warblers, Fantails and Silvereyes. We review the breeding history of White-faced Storm Petrels and Spotted Shags. Analysis of Australasian Harrier pellets showed that passerines were the most frequent prey and that carrion was taken from islands at least 2.3 km from the Noises. The contents of 13 Blackbird and four Song Thrush gizzards were also analysed. Houpara (Pseudopanax lessonii) fruit was present in 12 Blackbird gizzards and insects (mainly beetles) in eight. The thrushes had fed mainly on small snails and insects.