A rich fossil fauna accumulated by laughing owls (Sceloglaux albifacies) during the Holocene, is described from GD101 Cave, on the Gouland Downs, northwest Nelson, South Island, New Zealand. Twenty-eight species of bird, a tuatara, 3 frogs, at least 4 geckos, 1 skink, 2 bats, and 2 fish contribute to the species diversity. The fauna includes the first inland fossil record of New Zealand dotterel (Charadrius obscurus). The taphonomy of the deposit and the diet of the owl are discussed.
North Island robins are sexually dimorphic, males having darker plumage on their back and upper breast. However, males show delayed plumage maturation, and do not acquire the characteristic male plumage until after their first breeding season, 12-16 months after fledging. Therefore, sexing based on plumage alone will overestimate the proportion of females, and this may result in highly skewed sex ratios for translocations. Using measurements from robins of known sex on Tiritiri Matangi Island, I found tarsus length to be a useful indicator of sex. Of 82 robins measured, 80% of birds with tarsus length greater than 35.6 mm were male and 77% of other birds were female. If tarsus length is used in combination with plumage, it should allow sex ratios to be estimated reasonably accurately and without bias. However, additional data including wing chord measurements suggest that wing chord is superior to tarsus length for determining sex.
The population status of the Chatham Island tomtit (Petroica macrocephala chathamensis) was determined for each island of the Chathams group, east of New Zealand. Also, the breeding biology of the population on Rangatira (South East Island), which is free of introduced mammalian pests, was determined from observations made during 8 breeding seasons, 1981/82 to 1988/89. The total population of the Chatham Island tomtit is estimated to be < 1000 birds: Chatham, extinct; Pitt, c. 500; Rangatira, 200-300; Mangere, 70-100; Tapuaenuku (Little Mangere Island), occasional vagrant. Regeneration of scrub and forest habitats on 3 islands is likely to lead to gradual increases in the tomtit populations there. The nesting season on Rangatira was from late September to late January, which was just sufficient time for a pair to rear 2 broods successfully. Of 378 nests, 43% were in tangles of pohuehue (Muehlenbeckia australis) vines, 16% in cavities, 12% on a branch, trunk, or stump covered in vines, and for 21% the site was not indicated. The mean height of nests was 2.7 m, and the mean duration of the pre-laying period was 5.9 days. Mean clutch size was 3.1 eggs, and incubation usually started on the day the last egg was laid (82%). Only females were seen incubating, with males feeding their mates at regular intervals. Of 97 eggs, 83% hatched, and 93% of 15 nesting attempts resulted in at least 1 fledgling each. The high nesting success, in comparison to that of mainland populations, is attributed to the absence of mammalian predators on Rangatira. Although our study provided much information for the early stages of the nesting cycle, few data are available for other aspects of the Chatham Island tomtit’s breeding biology, such as length of incubation, and nestling and fledgling periods.
Reports of dispersal by juvenile weka (Gallirallus australis greyi) on the North Island are rare. Estimates of the distance dispersed and the rate of survival of dispersers are important factors to be considered for weka conservation. I captured 20 young weka during a 2-year study and attached radio transmitters to 4 of them. In addition, I was able to measure the distance travelled by 3 banded weka that were either recaptured or seen again, and 1 weka that was recovered dead. Newly independent weka used a part of their parental home range at first, then moved up to 3.5 km. Two-stage dispersal, where young weka leave their parents but remain close by and move away later, has been reported on offshore islands: my results are consistent with that type of dispersal. More research is needed on weka dispersal because it is likely to be linked to factors important for their conservation and management.