Publications Archive

We studied the breeding biology of a colony of Caspian terns (Sterna caspia) near Invercargill, New Zealand, during 1992 and 1993. The mean clutch size did not differ between years and averaged 2.04. Measurements of 147 eggs averaged 64.5 x 44.6 mm; there was no difference in size of A-eggs (1st-laid in a clutch) and B-eggs (2nd-laid) in either year, but the few C-eggs laid were significantly smaller. The incubation period averaged 27.2 days (range 26-29 days); some earlier published values of 20-22 days appear to be in error. In 1992, growth rates of A-chicks were significantly higher than those of B-chicks. Growth rates of A-chicks were significantly higher in 1992 than in 1993. Fledging occurred at 33-39 days at an estimated average mass of 527 g in 1992 and 501 g in 1993. Minimum productivity was 1.04 and 0.62 chicks fledged per pair in 1992 and 1993, respectively. Weather during the period of chick growth was much wetter and windier in 1993 and we suggest that this reduced the ability of parents to feed chicks. Investigator disturbance, which has been implicated in lower reproductive success in some studies of Caspian terns, did not appear to have a major impact in our study. We believe this was partly because the birds were habituated to our activities and partly because of our methodology.

We investigated the annual survival of Finsch’s oystercatchers (Haematopus finschi) breeding on farmland in mid-Canterbury, New Zealand. Annual survival from 1987 to 2000 averaged 0.892, with evidence of a small amount of variation in survival rates through time (estimated SD = 0.034). We found no indication that survival rates differed between males and females. However, recapture probabilities showed that males had stronger fidelity to breeding territories than did females. These results are similar to those reported from populations of H. ostralegus in Europe. Because oystercatchers are long-lived, the survival rate of adults is the key component in determining population size. Intensification of agriculture on the breeding grounds and disruption to coastal feeding grounds may reverse the trend for population increase in this species. Consequently, the survival rate presented here provides a basis for predicting future population trends.

The night-time activity of grey-faced petrels (Pterodroma macroptera gouldi) was measured at a colony on Tiritiri Matangi Island between 27 April and 10 December 1998. Considerable seasonal variation was observed (0 to >120 birds/night). A decline in numbers of birds at the colony in early June was likely resulted from the departure of both breeding (pre-laying stage) and non-breeding birds. Another decline at the end of September was most likely a consequence of the departure of non-breeding birds only. In general, as the season progressed there were fewer petrels per night, and they arrived later. The number of birds returning to the colony increased with increasing wind speeds and birds arrived earlier when winds were stronger. High wind speeds facilitate movement between breeding and foraging grounds for this pelagic species. A sampling period of 1 h from the arrival of the 1st bird provides sufficient information to discern definite patterns in numbers throughout the year.

Observations of eastern rosellas (Platycercus eximius) in the Wellington region were recorded during February 1994 to January 1997 by members of the Ornithological Society of New Zealand. Sixty-one percent of the 1227 sightings were made in 3 localities, Paraparaumu-Waikanae, Upper Hutt, and central Wellington. Most rosella sightings were in pastoral farmland (47%) and urban habitats, including parks, and golf courses (41%). Of the 400 sightings for which flock size was given, the mean was 3.6 rosellas, and flock size did not change significantly with season. Rosellas were seen feeding (n = 54) on buds and shoots (19%), flowers (5%), fruit (15%), and seeds (61%), with feeding on introduced plants making up 80% of the feeding observations.

The occurrence of musk ducks (Biziura) as fossils in New Zealand is reviewed and updated. Twenty-four bones from at least 7 individuals, and 67 elements from a single skeleton are known. Morphological differences between the fossils and the extant Australian B. lobata support continued distinction of the New Zealand form as the separate species B. delautouri.

Unusual bird records at the sub-antarctic Antipodes Islands from 1978 to 1995 increased the number of bird species recorded previously at the group by 15. The total avifauna now consists of 29 breeding species and 26 vagrant species.