Publications Archive

The Wellington branch of the Ornithological Society of New Zealand counted coastal birds along the shores of Wellington Harbour every month for two years in 1975-77 and again in 1986-88. Between the two surveys, giant petrels and Black-backed Gulls, which feed on offal, showed significant population declines; however, most other key species increased, particularly Little Shags, Little Black Shags and Mallards, presumably as the health of the harbour improved as discharges from abattoirs and sewer outfalls were reduced. The distribution of some species changed markedly between the surveys, away from Ngauranga and Pencarrow Head to Moa Point and Owhiro Bay, where raw sewage continued to be discharged into the sea.

The population dynamics of a local group of Kea (Nestor notabilis) was studied at a refuse dump in Arthur’s Pass National Park over the course of three successive summers. The mean number of birds that foraged at the dump during the summer was estimated as 20 juveniles, 10 subadults, and 36 adults. An average of 11% of these birds were females. The number of adults was quite stable across years. The total population of Kea in this area was estimated to be between 88 and 119, or in the order of 0.018 to 0.040 birds per hectare. Mortality did not exceed 16-20% per year for adult and subadult birds, but it was probably higher for younger birds. Male juveniles all appeared to disperse from the area within the first two years; female juveniles, on the other hand, were frequently resighted in subsequent seasons. This difference in behaviour was statistically significant. The abundance of fledglings suggested that as few as 10% of adult males may breed in any given year.

From 10 to 16 August 1991, we surveyed the complex of sounds making up Breaksea and Dusky Sounds, the Acheron Passage and Wet Jacket Arm, Fiordland, for Fiordland Crested Penguins. Two islands in Doubtful Sound were also checked. Minimum total estimates were 24 nests and 62 penguins in Doubtful Sound and 47 nests and-106 penguins in the Breaksea/Dusky complex. Penguins known to be on Breaksea I. and adjacent islands were not surveyed. Relatively more penguins were found nesting in caves or under rock overhangs and fewer were found in dugouts under trees than were found in the more northern sounds in 1990. No penguins were found on the many islands in Dusky Sound formed from steep-sided granite domes. The results support our suggestion made in 1990 that there are fewer than 1000 nests for the species annually.

In 1988, 3603 kilometres of the coast of New Zealand were patrolled and 7545 dead seabirds were found as part of the Beach Patrol Scheme. Two new species were the Tahiti Petrel (Pseudobulweria rostrata) and the Masked Booby (Sula serrator dactylatra). Unusual finds were a Black-bellied Storm Petrel (Fregetta tropica) and a White Tern (Gygis alba). A summary is given of the coastal and monthly distributions for 10 species of Puffinus found between 1943 and 1988. Of these shearwaters, the Sooty Shearwater (P. griseus) was found most frequently overall, mainly in May and November-December. This review of beach-wrecked shearwaters indicates that the information derived from the Beach Patrol Scheme for common seabird species relates reasonably well to the movements of these species about New Zealand coasts.

Differences in the time of onset of breeding, morphology, egg size, plumage and vocalisations of Dark-rumped Petrels (Pterodroma phaeopygia phaeopygia) were investigated on four islands in the Galapagos. Comparisons were made with P. p. sandwichensis in Hawaii. In Galapagos, breeding cycles differed among islands, and on San Cristobal there were two populations that bred at different times. On Floreana, colonies at different altitudes bred at different times. Eggs were laid on Santiago over four consecutive months; on Santa Cruz the egg-laying period was shorter. Analyses of morphological measurements and notional volume separated Galapagos Dark-rumped Petrels into three groups. Birds on Santa Cruz and those breeding in the middle of the year on San Cristobal were the smallest; birds on Santiago and those breeding at the end of the year on San Cristobal were of intermediate size; and those on Floreana were the largest. There was a similar size trend in the breadth and volume of eggs. No relationship was found between variable plumage patterns on head and chest or between plumage and island populations. Evidence is presented that supports sexual dimorphism in vocalisations, and it is suggested that males make Sweet calls and females make Coarse calls. There were statistically significant interisland differences among Sweet calls and among Coarse calls. Dialects probably exist within the archipelago. Calls had either one or two introductory syllables. When present, the second introductory syllable was very similar to the single introductory syllable, and these may serve the same function. Discriminant analysis of Sweet calls correctly classified 82.296 of these into island of origin. A similar analysis of morphology correctly classified 58.6% of birds from five populations. A theoretical combination of these two analyses indicates a potential classification rate of 92.6%. Although there are differences among Galapagos populations, there is not yet sufficient evidence to warrant subspecific status. Vocalisations of the Hawaiian birds were quite different from those in Galapagos, and Galapagos birds were bigger. Dark-rumped Petrels in Galapagos and Hawaii might be more distant taxonomically than currently recognised and they may be different species.