Publications Archive

Between 1961 and 1999 the number of adult sooty shearwaters found dead on beaches in northern New Zealand declined by about 64.4% and the number of fledglings by about 77.7%. Only 2 factors that we know about have been acting on the sooty shearwater population during the period studied and could have caused such a dramatic decline; a rise in sea temperature perhaps as a result of movement of the Sub-Antarctic Front and increase in harvest. Two other more recent phenomena, north Pacific fisheries mortality and climatic variation (El Niño Southern Oscillation and Pacific Decadal Oscillation), may be involved, but we cannot find any direct evidence of their impact in our data. The impact of this decline has been recently found on the breeding islands. More study is required to fully understand how weather, patrol frequency, deposition rate, persistence rate, and live bird numbers vary and interact. Deposition and persistence experiments similar to those reported from overseas need to be done in New Zealand.

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.

Dispersal within New Zealand of Australasian shoveler (Anas rhynchotis), banded as ducklings in Otago (n=489) and Southland (n=392) during 1971-1979, was determined from the locations at which 180 were shot by hunters. There were no statistically sigruficant differences in recovery distributions of Otago and Southland birds either when recovered in their year of banding (y-o-b) or in all subsequent years combined (later). About 50% of total recoveries were made in the y-o-b and 2-thirds of these from within 200 km of the banding site. Recoveries in later years were more widely distributed than those made in the y-o-b. North Island recoveries were 28% of total recoveries and were from most large coastal and lowland wetlands as far as Northland, 1400 km from the banding site. Recovery distributions of ducklings were not significantly different from those previously determined for moulting adults banded in the same areas. However, ducklings in their 2nd year of life appear to be more distantly dispersed from their natal sites than during their 1st year or are adults from their moulting sites. We speculate that long distance dispersal may be undertaken mostly by birds that fail to breed in their natal regions in their 1st year of life, and that dispersing birds may become irregular breeders at varying distant locations.

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=0.08). 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.

Brown teal (Anas chlorotis) populations at Clendon Cove and Tutaematai in Northland, New Zealand, declined catastrophically between 1993 and 1995, from 31 pairs to 1 and from 22 pairs to 8, respectively. Mean productivity was 1.8 fledglings pair1 in both populations. Fledgling survival was almost nil with only 1 of 51 identifiable fledglings surviving to recruit into 1 population. Almost all fledgling mortality occurred within 3 months of independence. Annual adult survival was 15% at Clendon Cove and 43% at Tutaematai and most deaths occurred in October-December, immediately after breeding. At Clendon Cove, significant mortality also occurred in autumn. Destruction of breeding and refuge habitat by cattle seeking moisture during periods of drought was identified as a significant cause of decline.

Bird records from the Snares Islands between Dec 1982 and Oct 2000 are summarised. Population estimates and distributions are given for the 29 breeding species. Bird species recorded breeding on the Snares Is for the first time since 1982 were southern black-browed albatross (Diomedea melanophrys), Chatham Island albatross (D. eremita), mallard (Anas platyrhynchos), southern black-backed gull (Larus dominicanus), fantail (Rhipidura fuliginosa), and starling (Sturnus vulgaris). Fantails are now abundant on the Snares Is. Published work on the breeding chronology and breeding success of 8 intensively studied species is summarised, and new information on breeding ecology is presented for all breeding species. Sighting of 70 non-breeding and vagrant species are summarised; 34 of these were new records from the Snares Is since 1980. The total bird list for the Snares Is is now 99 species, with a further 8 species reported from boats offshore.

The population of white herons (Egretta alba) at Waitangiroto Nature Reserve has been monitored since 1944. The number of breeding adults (estimated from maximum number of nests at the height of the breeding season, and first recorded in 1958) has increased from 26 to c.100, with a concurrent increase in the number of chicks hatched and fledged. Population growth was greatest between 1964-69 and 1980-84. Chick mortality appears to result largely from the effects of westerly and southwesterly storms in October and November, although infanticide, siblicide, and low levels of predation may account for some chick deaths. The mean number of fledglings nest^-1 has decreased over time as the number of nests has increased, suggesting a density dependent response. The white herons that “invaded” New Zealand from Australia in 1952 and 1957 did not appear to recruit into the breeding population.

The benefits of monitoring habitat use patterns of translocated populations are widely acknowledged. However, this monitoring seldom occurs. Here, I report the habitat use and foraging patterns of a newly translocated population of South Island saddlebacks (Philesturnus carunculatus carunculatus) on Motuara Island, New Zealand, during the 1st breeding season after release. Reintroduced South Island saddlebacks spent most foraging time on the ground and in Pseudopanax arboreus. Foraging substrates used by male and female saddlebacks differed significantly Saddlebacks focused foraging activities at 0-4 m above ground, and appeared to prefer to forage in larger trees, although the species composition of forested areas did not seem to influence the birds’ choices of places to settle. With increasing population density, saddlebacks on Motuara Island may increase their areal foraging eficiency by using a wider range of plant species, vertically stratifying foraging locations within pairs, increasing use of smaller trees for foraging, and possibly by using scrub habitats more extensively South Island saddlebacks appear to be highly adaptable in their choice of foraging sites and this plasticity may enhance the success of translocations.