The brown teal (Anas chlorotis) is a threatened duck endemic to New Zealand, whose single remaining stronghold is on Great Barrier Island. During a study at Awana from 1985 to 1987 it was concluded that the population was stable. We evaluated this proposition by analysing counts made at flocking sites between 1985 and 2001, examining their demography, and by developing an age-specific demographic model to predict the likely persistence time of the population. Numbers of teal at flocking sites declined between 1985 and 2001 though demographic variables did not change except for duckling survival rate, which increased from 26% during 1996 to 54% during 1999. Previous predictions of stability were based on an incorrect model and our model suggests that the brown teal population will halve every 4.1 years. The decline observed since 1987 could be halted by improving adult survival rate.
The reproductive biology of red-crowned parakeets (Cyanoramphus novaezelandiae novaezelandiae) was studied on Little Barrier Island (Hauturu) during the 1989/90 and 1990/91 breeding seasons. Nests sited in cavities of pohutukawa (Metrosideros excelsa) and puriri (Vitex lucens) trees accounted for all but 1 nest which was found in a hole in the ground. Breeding activity was recorded from Nov to Mar with peak egg laying in Dec. Mean clutch size was 7.0 eggs (range 4-9). Replacement clutches were rare and only followed the loss of young broods. Female parakeets were entirely responsible for incubation that lasted about 23 days. The nestling period averaged 40.8 days (range 32-49) with about a 30% probability of an egg resulting in a fledgling. The main cause of nestling mortality was starvation. Infestation of nests by mites and predation of nestlings were also occasionally recorded. Post-fledging mortality was high, particularly in the 1st 2 weeks, and was attributed mainly to aerial predators such as morepork (Ninox novaeseelandiae). Aspects of nest and roost site characteristics, brood reduction, mortality, and vulnerability to predation are discussed in relation to the conservation of the species.
More than 35,000 southern royal albatrosses (Diomedea epomophora) were banded on Campbell Island from 1941 to 1998. Recoveries of 2187 birds while breeding on Campbell Island during 1994-98 included 54 (2.5%) that were injured by their bands; over all years, 195 (3.4%) injured birds and 225 others with bands fitted incorrectly were reported. Injury rates were higher for birds banded as chicks (7%) than adults (0.5%). Untrained volunteer banders from the island’s meteorological station banded up to 5200 birds annually, and in some years bands were not closed properly. The partially open bands eventually embedded in the leg or ankle, crippling the birds. Six annual banding cohorts were responsible for 83% of injuries and almost half (n = 90) came from the 1979 cohort. Banding quality improved after 1982 and only two injured birds have been found from more recent cohorts. The band’s large circumference relative to its thickness may have contributed to it springing open with time, so a stronger band is recommended. For animal welfare reasons, a band repair operation should be conducted. If nothing is done, the situation will improve over the next 20-30 years as birds die, but regular band maintenance would prevent future problems.
The aim of this study was to associate the distribution of waders (Charadriiformes) with physical attributes of estuaries and map the distribution of estuaries that have the potential to support large diverse wader populations. Maximum wader abundance and the maximum number of species recorded (1983-1994) at 94 estuaries on the North Island, New Zealand were related to physical attributes of the estuaries using General Linear Modelling techniques. Parameters describing the estuary type, area, tidal influence, catchment area, catchment rainfall, intertidal area and temperature were used as independent variables. Anaiysis revealed strong positive relationships between the size and diversity of a wader population and estuary area. A negative relationship between catchment runoff and wader abundance and diversity existed in some estuaries. The model predicted that relatively small estuaries (100 to 999 ha) could support large, diverse wader populations if catchment runoff was low. A map of estuaries predicted by the model to support large diverse populations of wading birds is presented. This study highlights the value of large estuaries in New Zealand in maintaining large populations and high species diversity of migratory and nonmigratory waders.