The measurements of the Redpoll (Carduelis flammea) in Canterbury, New Zealand, were investigated. Variation in plumage colour are compared with study skins and published data for British Redpolls. New Zealand and British Redpolls are shown to differ and it is suggested that differences may be due to ‘founder effect’ rather than ‘hybridisation’ between two or more introduced races, as had previously been postulated. The occurrence of light-coloured plumage was more common in males. Females showed a much wider range of poll colour.
From available records ranging from systematic surveys to casual observations, the known distribution of Buller’s Shearwater (Puffinus bulleri) in the North Pacific Ocean is described. The birds arrive in subarctic waters in June and slowly expand northward and eastward as far as the Gulf of Alaska by August. The mid-ocean distribution after August is poorly known, but many birds, presumably non-breeders, are along the west coast of North America, at least from British Columbia to southern California, until late October-early November. Numbers observed along this coast have increased since the mid-1960s.
I investigated the relationship between floods on the riverbed breeding grounds of Wrybills (Anarhynchus frontalis) and the number of Wrybills censused on northern harbours the following summer. For the purposes of the study I assumed that most birds oversummering on northern harbours are first-year non-breeders and that flood flows of the Rakaia River are representative of most other Wrybill breeding rivers. A highly significant negative correlation (r2=0.69; p<0.01) existed for the 1968-1982 period. The study’s findings provide some support for the observation that by the early 1960s the Wrybill population, after many years of growth, had begun to stabilise. Serious flooding in the 1982 and 1983 breeding seasons may have again destabilised
the population structure.
In Canterbury, Caspian terns (Hydroprogne caspia) nest
mainly as single pairs associated with colonies of Black-backed
gulls (Larus dominicanus) on shingle riverbeds. Of 37 nests
studied, 28 (75%) hatched and 20 (54%) produced a total of
21 flying young, each pair raising an average of 0.6 young per
season. The low productivity is attributed to reduced prey
availability.
Two counts of skuas (Catharacta maccormicki) at Cape Hallett were made between 17 and 20 January 1983: in one 85 pairs and 83 non-breeding birds, total 253 birds; in the other, 83 pairs and 79 non-breeding birds, total 245 birds. South Polar Skua numbers remain low, suggesting a continuation of the 1960s decline or the influence of climatic factors such as heavy snowfall during critical stages of skua breeding.