Publications Archive

Many aspects of the ecology of the endemic variable oystercatcher (Haematopus unicolor) have not been studied in detail. We colour-banded and monitored a population of the species in a study area between 36°S and 37°S on the east coast of the North Island, New Zealand. Monitoring was intensive during the breeding season from 1994/95 to 1998/99, during which time we gathered information on timing of breeding, chick growth, and productivity. We also recorded measurements of adult birds and eggs. Laying of first clutches was protracted and extended from early September to mid-December. Chicks fledged at lower weights than adults and with shorter total head length and wing, but with tarsus and mid-toe within the adult range. Productivity at four core breeding sites within our study area averaged 0.42 chicks fledged per pair per year. Juveniles commonly remained with their parents on their natal territory during their first winter. From 1999, monitoring was less intensive as we continued collecting data on dispersal, age at first breeding, survival, and pair-bond retention. Natal dispersal values ranged from 0–109 km, with most birds breeding within 60 km of their natal site. As with many oystercatcher species, maturity is delayed, and birds in our study area first bred at between 4 and 8 years of age. There was a high level of mate-fidelity, with one pair-bond lasting 16 consecutive years, but divorce was not uncommon. Once established on a territory, adults were highly sedentary. Annual survival rates of adults and pre-breeders were very high, and the local population had the capacity to grow by about 5% per year. Birds breeding at low-lying sites often lost nests to flooding, and this threat is almost certain to be exacerbated by ongoing climate change.

Abstract: Moult is a vital avian process because it allows the renewal of the worn plumage in an organised way. Moult has a circannual periodicity and tends to differ between the first annual cycle (post-juvenile moult) and subsequent ones (post-breeding moult) of passerines, a fact that can be used to determine the age of individuals. We estimated wing-feather and rectrix moult-extent for 17 New Zealand passerines (excluding introduced species), classified each bird according to eight moult patterns, and computed frequency of wing-feather and rectrix replacement. We combined post-juvenile moult information with that of maturation of feathered and unfeathered characters to provide guidelines for age determination. Our results cover an important gap in the knowledge of the natural history of New Zealand passerines, generate reliable age determination criteria, and thus providing essential information for future conservation actions (including translocations) and to test hypotheses on the ecology and evolution of avian moult in the Australasian region.

Shorebird nest outcomes can be affected by factors such as predation, human disturbance, and habitat characteristics. Over two breeding seasons between 2022–2024, we monitored the hatching success of banded dotterels (Anarhynchus bicinctus), southern black-backed gulls (SBBGs) (Larus dominicanus), black-fronted terns (Chlidonias albostriatus), pied stilts (Himantopus leucocephalus), and variable oystercatchers (Haematopus unicolor) at the Ashley River estuary, New Zealand, and compared these values to those in the literature. We also recorded habitat variables at the nest sites of the two species with the largest sample sizes: banded dotterels and SBBGs. Hatching success was lowest for black-fronted terns and highest for SBBGs. Overall, failure was predominantly due to predation and flooding. SBBG hatching success was unrelated to the measured nest site variables but may have been influenced by seasonal changes, with earlier nests appearing more successful. Banded dotterel nests that were closer to water appeared to be more successful, as did nests in the first year of the study. Cats (Felis domesticus) were recorded depredating banded dotterel nests, highlighting the importance of monitoring and controlling invasive species to protect native birds in New Zealand’s estuaries.

Holdaway, R.N.; Allentoft, M. E. 2022. A basic statistical approach to determining adult sex ratios of moa (Aves: Dinornithiformes) from sample series, with potential regional and depositional biases. Notornis 69: 158-173.