We investigated the use of call count surveys to monitor weka numbers for management purposes. A Generalised Linear Model based on data from 11 1 nights of listening for weka at Rakauroa (North Island, New Zealand) showed that the number of calls recorded was influenced by listening site and month, but not by wind direction, wind strength, cloud cover, phase of the moon, rainfall or temperature. Mean number of calls heard was highest between December and March, with a peak in January. More birds were heard from certain listening sites. Although there was no correlation between any of the environmental variables and weka calling, wind, and rain may have reduced the audibility of weka in other studies. The estimated probability of detecting weka was 60-80% (mean = 728). At least 3 nights at each listening station were necessary to improve the census accuracy. Call counts of weka at Rakauroa between 1993 and 1997 showed a decline in the number of weka.
The total population of North Island weka (Gallirallus australis greyi) is about 4150 adults spread over five islands, one North Island population, and a number of captive birds in aviaries and mainland island programmes. Between 77% and 84% of the adult weka population are on Kawau Island. Density changes in the Mansion House Historic Reserve, and anecdotal records suggest that adult weka populations on Kawau Island has fluctuated between c.2100 and c.5000 during 1992-1999. The largest declines occurred within 12 months of the 1990-91 and 1997-98 droughts.
The South Island saddleback (Philesturnus carunculatus carunculatus) is one of two subspecies of the New Zealand saddleback. Despite the endangered status of this subspecies, it was not studied in detail until 1994, when 26 birds were released onto Motuara Island in the Marlborough Sounds of New Zealand. I report the foraging behaviour and diet of this reintroduced population during the first breeding season after release. South Island saddlebacks used their bills in a variety of ways when foraging, and were predominantly insectivorous. They obtained most food from the ground and five-finger (Pseudopanax arboreus), and the number of prey captured generally reflected the amount of time saddlebacks spent on foraging substrates. North and South Island saddlebacks are very similar in terms of foraging behaviour, prey handling techniques and types of invertebrate prey consumed. The foraging patterns and diet of South Island saddlebacks on Motuara Island differed from all potential competitors. I conclude that the success of the South Island saddleback transfer to Motuara Island should not be threatened by a lack of food or foraging opportunities.
During the 1997/98 breeding season we counted the breeding populations of Chatham Island shag (Leucocarbo onslowi), Pitt Island shag (Stictocarbo featherstoni) and black shag (Phalacrocorax carbo). Surveys, on foot or from kayaks and fishing boats, of all potential shag nesting habitat within the Chatham Islands provided the first complete census for shags breeding there. The breeding population of Chatham Island shag was 842 pairs in 10 discrete colonies, while there were 729 breeding pairs of Pitt Island shag at 63 locations throughout the group. Given that the counts of the endemic shags are for the total world populations. these species are extremely rare. The black shag breeding population was 233 pairs, in 5 locations on Chatham Island only. Comparisons with counts made during the 1960s and 1970s by visiting ornithologists suggest that the populations of Chatham Island shag and black shag have remained relatively stable, although the distribution of colonies of both species has changed significantly. Too few previous counts of Pin Island shag colonies were available to determine a population trend. All 3 species are threatened in the Chatham Islands by destruction of nesting habitat, disturbance of nesting colonies, human persecution, and predation by introduced mammals.