Observations of birds were made while working on fishing trawlers intermittently for a total of almost a year in New Zealand subantarctic waters. Large numbers of several species of albatrosses and petrels are attracted to trawlers to scavenge and their numbers vary throughout the year. Species not attracted are seen less commonly. Scavenging behaviour around trawlers is discussed. There seems to have been an increase in scavenging by certain species in the last 30 years.
There are major sexual differences in the calls of thin-billed prion Pachyptila belcheri. This allowed birds to be sexed initially by calls, and then by their measurements. Males were on average larger than females for six out of eight morphometric characters, with the greatest difference being in the bill. We then investigated the possibility of sexing birds on the basis of external measurements: a discriminant function analysis based on the eight measurements allowed correct classification of 84.4% of the 281 birds. In 89% of breeding pairs, males had greater bill depth than their partner. A stepwise discriminant analysis revealed that bill depth, head length and body weight were the three most discriminant variables. The combinations of two measurements (bill depth and body weight, or bill depth and total head length) allowed correct classification of 84.3 and 83% of the birds respectively, whilst a classification solely based on bill depth gave a 83.2% correct classification. The degree of sexual dimorphism in this species is similar to that found in other tubenoses.
Kaka (Nestor meridionalis) less than one year old can be distinguished from older birds by a pale ring of skin around the eye (periophalmic ring). In birds less than five months old this has a yellow tinge, as does the cere, gape and the soles of the feet. A further distinguishing feature of kaka between three and six months of age are protruding rachides (feather quills) on the tips of the tail feathers. On Kapiti and Little Barrier Islands, most kaka nestlings fledge in February and receive food from their parents until June or July. Fledglings can often be detected during this period by their conspicuous and frequent food-begging behaviour. Juvenile characteristics in the kaka persist for a much shorter period than in the kea (N. notabilis), its sole extant congener. The loss of juvenile characteristics prior to sexual maturity suggests that juvenile kaka becomes socially independent of adults earlier than kea, presumably because of more readily obtainable food sources in their environment.
During a census in gardens in Hamilton, 71.8% of the 4428 birds observed belonged to introduced species. A total of 15 species were observed. Bird species richness was positively correlated with native plant biomass and, more strongly, with total plant biomass. More birds were present in gardens with more native plants. Among the most common species, the abundance of the house sparrow (Passer domesticus) decreased with increasing percentage of native plants, the silvereye (Zosterops lateralis) increased, while blackbirds (Turdus merula) and starlings (Sturnus vulgaris) showed no significant change. This was typical for other introduced bird species. Most other birds, including the fantail (Rhipidura fuliginosa) and the grey warbler (Gerygone igata), were most abundant in gardens with higher native plant biomass. Notable was the absence of the tui (Prosthemadera novaeseelandiae) from all censused areas in Hamilton at the time of observation. No significant variation between morning and evening samples was noted.
During 1993, participants in the Beach Patrol Scheme patrolled 2954 km of the New Zealand coastline. 4295 dead seabirds of 55 species, plus 117 individuals of 28 other bird species were found. The number of seabirds found in 1993 was only 43% of the annual average of 9997 birds between 1971 and 1992, and was the eighth consecutive year that below average numbers of dead seabirds have been found. Unusual finds were three yellow-nosed mollymawks (Diomedea chlororhrynchos), two grey-backed storm petrels (Oceanites nereis) and a New Caledonian petrel (Pterodroma leucoptera). A summary is given of the coastal and monthly distributions of three Sterna species found between 1943 and 1992. Just nine black-fronted terns (S. albostriata) were picked up, mainly along eastern and northern South Island coasts. Of 239 Caspian terns (S. caspia), most were found on Auckland West, Auckland East, Bay of Plenty and North Coast South Island beaches. There was no significant change in the recovery rate of Caspian terns through the year. 1738 white-fronted terns (S. striata) were found, with a peak in mortality during autumn.
A colour-banded population of riflemen at Kowhai Bush, Kaikoura, New Zealand was studied to determine the contribution of males to the care of young. Parental care and territorial behaviour were qualitatively the same throughout the breeding period. Males fed the females during courtship and in this way contributed the food required to produce the first clutch of eggs. Males made 66% of nest-building visits (early nests), spent 50% more time incubating than their mate by day (both clutches), leaving the females the thermo-insular advantage of incubating at night, always fed young significantly more often than their mate and contributed 55-77% of all food items fed to broods without helpers (the great majority of nests), and shared territorial defence equally with their mate. However, nest-building and territorial defence occupied less than 1% of parents’ time early in the breeding season. One widower was unable to fledge young alone. Early season sex ratios for the years studied were (M:F) 22:15, 50:35, 39:37 and 20:21 with extra males sometimes becoming helpers. The male’s high parental effort was not reflected in significantly lower survival to the next breeding season. Possible reasons for the large contribution by the male rifleman to the breeding effort are discussed.
Between 1940 and December 1993, 66 species of landbirds (including shore and freshwater birds) were recorded at the Chatham Islands. Of these, 38 were native and introduced breeding species, 4 were regular summer visitors and 24 were occasional visitors or stragglers. Published and unpublished records of these species on the Chatham Islands are summarised.
The diet of red-crowned parakeets (Cyanoramphus novaezelandiae chathamensis) and hybrids (C. n. chathamensis x C. auriceps forbesi) was determined from crop contents and field observations. Crops were dissected from 220 red-crowned and hybrid birds collected over four years on deforested Mangere Island in the Chatham group. Volume and prevalence of foods taken in winter, spring and summer were measured. No effect of sex or age was found on frequency of occurrence of food items, and low variation in diet attributable to species hybrid status indicated that feeding strategies of the parent species had converged. Diet of all forms varied seasonally. The main winter food was grass seeds, with a small proportion of leaves. The spring diet was the most varied, consisting mostly of leaves, with seeds, flowers and invertebrates. Seeds were eaten in late summer, mostly from Geranium traversii. Field observations in winter emphasised the importance of leaf feeding. Some plant species seen to be eaten in summer were not found in crops. Habitat selection and perch height distribution was associated with breeding requirements as well as feeding.