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Sexing Grey-faced Petrels by discriminant analysis of measurements

Notornis, 39 (4), 261-265

R.M. Johnstone, B.E. Niven (1989)

Article Type: Paper

Discriminant function analysis was used to calculate classification formulae for predicting the sex of 98 adult Grey-faced Petrels (Pterodroma macroptera gouldi) at the start of incubation. Body weight, bill length, bill width, and bill depth all showed statistically significant sexual dimorphism. A classification formula based solely on bill measurements is impractical for sexing Grey-faced Petrels because of 37% error. The combination of body weight and bill depth in the formula proved useful, correctly classifying 92% of birds. This method provides a simple and reliable way of sexing Grey-faced Petrels in the field just after laying. Cloacal examination also allows definitive sexing at this time.

Cavity Nesting in Stitchbirds and the use of Artificial Nest Sites

Notornis, 36 (1), 27-36

G. Rasch (1989)

Article Type: Paper

Cavity nesting by Stitchbirds (Notiomystis cincta) was studied on Little Barrier Island by adding artificial nest sites (boxes) in a breeding habitat. The addition of boxes was a test of the theory that the number of breeding pairs of cavity nesting species is limited by the availability of suitable holes for nest sites. Site limitation is also said to prevent males of these species from taking more than one mate. This theory was tested by placing some boxes close to natural nest sites and other boxes. Results showed that the number of breeding Stitchbirds was not necessarily limited by the availability of sites, and that lack of sites did not restrict male birds to monogamy.  The boxes could be a useful management tool for enhancing this rare species.

The Effects of Wind and Sea on the Feeding of Antarctic Terns at the Snares Islands, New Zealand

Notornis, 36 (3), 171-182

P.M. Sagar, J.L. Sagar (1989)

Article Type: Paper

The effect of wind and sea conditions on the feeding of Antarctic Terns (Sterna vittata bethunei) was studied during three visits to the Snares Islands. The terns preyed upon fish and swarms of crustaceans. Increasing wind speed significantly reduced the terns’ capture rate and feeding success. The terns fed in similar ways with calm and moderate seas. However, rough seas significantly reduced the attempt rare, capture rate, and feeding success of terns feeding on fish and the capture rate and success of terns feeding on crustaceans. Foraging techniques varied with the type of prey sought and sea conditions. To catch fish, the terns mostly plunge dived in calm seas but contact dipped for 40-46% of attempts in moderate and rough seas. They caught crustaceans mainly by contact dipping, but used partial plunge diving more in moderate and rough seas. Wind speed and sea conditions seemed to affect terns feeding on crustaceans by making prey move away from the surface. Several other species of seabirds joined the terns to feed on crustacean swarms. Interspecific interactions were minor; however, large flocks of Sooty Shearwaters (Puffinus griseus) displaced terns from feeding on swarms.

Bird Counts in Regenerated Urban Forest at Auckland Domain

Notornis, 36 (2), 81-87

B.J. Gill (1989)

Article Type: Paper

From April 1987 to April 1988 (inclusive) I completed 195 5-min stationary bird counts at two forested sires in the Auckland City Domain. Auckland Domain has 22 species of passerines and near-passerines, more than half of them introduced.  The mean annual counts – the first published for the North Island – showed a very high incidence of Silvereyes, Blackbirds and Fantails compared with beech-podocarp forests and conifer plantations of the northern South Island, and a low incidence of Grey Warblers and Shining Cuckoos. Whether these are general characteristics of northern or urban forests awaits further study.

Incubation and early chick-rearing in the Grey-backed Storm Petrel (Garrodia nereis)

Notornis, 36 (2), 141-147

A.R. Plant (1989)

Article Type: Paper

The breeding of the Grey-backed Storm Petrel (Garrodia nereis) at Houruakopara Island in the Chatham Islands (44° 06′ S, 176° 31′ W) was investigated and the nest site, egg, and chick are described. Both parents incubated the egg in poorly synchronised shifts averaging 1.9 days. generally followed by a desertion period of 2.7 days. Eggs hatched from mid-November, and the chick was brooded by either parent for up to 4 days after hatching. Chicks were fed on average every 1.6 days and the size of each feeding increased with age.  The average daily increase in body weight was 12.6%, and by 17 days the weight of the chicks equalled that of the adults. Evidence of competition for nest sites within the species and with Broadbilled Prions (Pachyptila vittata) and Little Blue Penguins (Eudyptula minor) is discussed and a list of food items taken from regurgitations is presented.
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