The incidence of predation on house sparrows (Passer domesticus) and hedge sparrows (Prunella modularis) by captive brushtail possums (Trichosurus vulpecula), and the bird tissues consumed following predation, were recorded over 26 weeks in a facility where possums were housed in single sex groups. A total of 44 sparrow carcasses was recovered; on average 1.7 birds were killed per week (range 0-9 sparrows per week) in pens that each housed 8-12 possums. Tissue was eaten from fewer than half (48 %) of the birds killed. There were no significant differences in the incidences with which different tissues (brain, breast, legs, or viscera) were eaten. This study corroborates observations of bird predation by possums in the wild. Importantly, it shows that a high proportion of birds killed by possums are not eaten.
We compared the behaviour, energy expenditure, and food intake of male and female South Island pied oystercatchers, Haematopus ostralegus finschi, breeding in pasture and crop paddocks in Canterbury. In this monogamous species, females spent more time inactive than males (P=0.03) and there was a trend for males to spend more time in territory defence than females (P=O.O8). There were no significant differences in other behaviours and the sexes did not differ in their food intake rates. We used literature values for this species to estimate the energy expended in each activity and the energy expenditure rate over the breeding season. Despite the differences in the proportion of time spent in territory defence and inactivity by the sexes, males had a lower rate of energy expenditure than females over the breeding season (P=0.07). We suggest that behavioural differences are unlikely to compensate female South Island pied oystercatchers for their costs of gamete production and the difference in energy expenditure may reflect the uncertainty of paternity of males.
Nesting pairs of brown skuas (Catharacta lonnbergi), black-backed gulls (Larus dominicanus), red-billed gulls (Larus novaehollandiae), white-fronted terns (Sterna striata), Chatham Island oystercatchers (Haematopus chathamensis) and shore plovers (Thinornis novaeseelandiae) were counted during 10 seasons on Rangatira (South East) and Mangere islands of the Chatham Islands. It was concluded that the small numbers of skuas, oystercatchers, and shore plovers on the islands was a result of habitat shortage, but that populations of the colonially-breeding gull and tern were constrained by food limitation in the surrounding seas. Whereas skuas, black-backed gulls, and terns nested in the open with conspicuous nests the other shore species on the islands had concealed nests. Comparison with nesting on Chatham Island, the New Zealand mainland, and subantarctic islands suggested that concealed nesting by red-billed gulls, oystercatchers and shore plovers was most likely in response to the presence on the islands of the predacious brown skua.
The blue penguins (genus Eudyptula) have been subjected to extensive taxonomic revision. In 1976, the genus was reduced from 2 species to a single species (Eudyptula minor) with 6 subspecies, based on a morphometric analysis. Despite the later proposed rejection of the differentiation of subspecies in Eudyptula minor, following analysis of allozymes in some populations, the 6 subspecies have continued to be recognised in some popular and scientific literature. We compared the sequences of 3 mitochondrial gene regions (small ribosomal subunit, cytochrome oxidase b and the control region) from the 6 hypothesised subspecies to examine relationships within Eudyptula. We found evidence for 2 unexpected clades: the 1st consisting of Otago and Australian populations, the 2nd consisting of north- ern, Cook Strait, Chatham Island, and Banks Peninsula populations. Some support for these 2 clades was also found from a re-analysis of morphometric data and from a preliminary examination of vocalisations.
The population of Providence petrels (Pterodroma solandri) that nested on Norfolk Island at the time of 1st European settlement of that island in 1788 was probably >1 million pairs. Available evidence indicates that Europeans harvested many more Providence petrels in the years immediately after settlement than previously believed. About 1,000,000 Providence petrels, adults and young, were harvested in the 4 breeding seasons from 1790 to 1793 alone. Despite these enormous losses, many Providence petrels were apparently still nesting on Norfolk Island in 1795 when they are last mentioned in documents from the island. However, any breeding population that may have survived there until 1814 when Norfolk Island was abandoned temporarily was probably exterminated by the combined activities of introduced cats and pigs which had become very numerous by the time the island was re-occupied in 1825.
We investigated whether breeding frequency and breeding success of southern Buller’s mollymawks (Thalassarche bulleri bulleri) were influenced by breeding experience and pair bond duration, using data from annual checks at 3 study colonies at The Snares from 1992 to 2001. Most pairs bred annually irrespective of the experience and length of the pair bond, although the proportions that did so varied with pair type. Thus, breeding frequency (% breeding in consecutive years) was lowest among pairs of 1st-time breeders (77%). Breeding frequency of those pairs after their 2nd attempt (89%) became similar to that of established pairs together for at least 1 previous breeding attempt (88%), or newly formed pairs in which one or both birds had previous breeding experience (91%). Overall breeding success was 71% and, in established pairs, breeding failure (loss of egg or chick) was associated with reduced breeding frequency (83% compared to 91% when successful). Lowest breeding success (58%) was associated with the attempts of 1st-time breeders. Performance of these pairs improved until the 3rd attempt (81%), when it became similar to that of established pairs (73%) and newly formed pairs in which one or both birds had previous breeding experience (77%). Divorce was rare (1.1-3.5% annually). First-time and former breeders mated more frequently with birds of similar status (85% and 58% respectively) than expected assuming random pairings. When changing partner, as a result of divorce or death, the average interval before breeding again was 2.1 years for males and 2.6 years for females, and so, on average, each change of partner resulted in the loss of 1 breeding attempt. Thus, the time taken to obtain a new partner has a lifetime reproductive cost.