Discriminant function analysis (DFA) was used to determine gender and geographic variation in the morphometrics of white-chinned petrels (Procellaria aequinoctialis) measured from fisheries bycatch in New Zealand. Samples were divided into 5 clusters based on capture location. A DFA model was created using adult breeding birds presumed to be from the 2 main locations at the Auckland Islands and Antipodes Islands. Geographic variation in head and bill, skull width, culmen, culmen depth at base, culmen width at base, right and left mid-toe and claw, tail, and right and left wing was found between birds presumed to be from the ‘Auckland’ and ‘Antipodes’ clusters, with ‘Antipodes’ birds being generally larger than ‘Auckland’ birds. Gender variation in head and bill, skull width, culmen, culmen depth at base, culmen width at base, minimum bill depth, right and left mid-toe and claw, right wing, right and left tarsus existed for ‘Auckland’ birds. Gender variation in head and bill, skull width, culmen, culmen depth at base, culmen width at base, minimum bill depth, right and left mid-toe and claw, and tail existed for ‘Antipodes’ birds. Birds in the other 3 clusters were classified as originating from the Auckland Islands or Antipodes Islands. The clustering suggested that birds from the Auckland Islands tended to forage mostly north and west, whereas birds from the Antipodes Islands foraged mostly towards the north. There were large overlaps at Puysegur Point and particularly the Chatham Rise of birds from both breeding locations. This study shows the usefulness of bycatch necropsies, and emphasises the need for further studies in geographic variation and sexual dimorphism at all New Zealand breeding locations.
The Chatham Island duck (Anseriformes: Anatidae: Anas chathamica) had a pronounced and rugose enlargement to the tip of the processus extensorius at the proximal end of its carpometacarpus. This “carpal knob” was the equal in size of those found in some much larger waterfowl (e.g., steamer ducks, Tachyeres sp.), and was disproportionately larger than those of all other New Zealand waterfowl. The knobs on 20 carpometacarpi examined all showed evidence of continuous bone deposition at their tips and their use as weapons is implied. Comparisons with other duck species having similarly prominent and rugose carpal knobs suggests the Chatham Island duck maintained long-term pair bonds and occupied combined feeding and breeding territories year-round which both sexes defended belligerently.
Banded rails (Gallirallus philippensis) were surveyed in saltmarshes and mangrove fringed habitats at Onerahi, Whangarei, New Zealand. A total of 13 sites were surveyed 3 times per year around sunset during late spring in 2004, 2007 and 2013. On average 4.41 calls were heard per hour. Banded rails were detected at 12 sites with between 0.01 and over 2 ha of saltmarsh and extensive mangroves, but not a saltmarsh site lacking mangroves. Occupancy models favoured those with no change in occupancy state, seasonal detection, and there was with some support for random colonisation of sites. Records from Awaroa Creek indicate that rails can be detected from late afternoon calls throughout the year. Surveys should include the half hour before until at least 10 minutes after sunset.
Discriminant function analysis (DFA) is widely used to determine sex in the field from morphological measurements of bird species with monomorphic plumage. Sexual dimorphism was examined in black petrels (Procellaria parkinsoni) using 7 external measurements of adult birds breeding on Great Barrier Island, New Zealand. Males were significantly larger than females in absolute values of all measurements except for tarsus. Two stepwise DFA models were developed. The first used all 7 parameters, while the second model used only 6 parameters in order to increase sample size. Model one and two showed an 88 and 82% classification success, respectively, most likely due to the high overlap in measurements between males and females. These canonical functions were not accurate enough for field surveys, but may be improved using a larger and more representative sample size.
Flesh-footed shearwaters (Puffinus carneipes) are considered to be one of New Zealand’s seabird species that is most heavily impacted by both commercial and recreational fisheries, yet they have an IUCN ranking of “Least Concern”. To resolve this contradiction we conducted surveys on 3 large breeding colonies and compared our results to historical data. We found that the burrow density on the most northerly island (Lady Alice Island/Mauimua) has increased since the last set of surveys; however the density of flesh-footed shearwaters nests has remained stable. At the largest colony we surveyed (Ohinau Island), the density of burrows has remained stable, while the density of nests has declined. At New Zealand’s most southerly colony (Titi Island), both burrow and nest densities have remained stable. Our results suggest that the status of flesh-footed shearwaters populations in New Zealand is variable with 2 populations that are stable and 1 that is declining. Nevertheless, due to the short time period between our surveys and the historical data, repeated surveys in the future are needed to determine if further declines in the largest colony warrant a reassessment of the status of this species.
Of 4 importations of Canada goose Branta canadensis into New Zealand, 2 (in 1905, 1920) resulted in breeding. Commencing in 1907, multiple and repeated releases of the 1905 geese and their progeny had, by 1922, established flocks of several hundred distributed along the eastern Canterbury and Otago foothills of the Southern Alps. Thereafter, the geese spread widely but remained resident and breeding only in the South Island. Establishment of Canada geese in North Island commenced in 1969 with the first of 4 transfers by the Wildlife Service, collectively totalling 280 birds from Canterbury’s Lakes Ellesmere and Forsyth, to coastal Wairoa lakes and nearby locations. The Wildlife Service assisted numerous other transfer and release initiatives, of at least 800 birds, in North Island in the 1970s and 1980s, principally by Wellington and Auckland Acclimatisation Societies, Ducks Unlimited, and private waterfowl enthusiasts. At the same time it supported transfers of 450 geese to the South Island’s West Coast. From these multiple releases Canada geese have become widespread in rural New Zealand.
Kiwi (Apteryx spp.) are the most vocal of the ratites. Of the 5 Apteryx species only 2 have previously been subject to detailed vocal analysis: the North Island brown kiwi (A. mantelli) and the little spotted kiwi (A. owenii). This paper describes the vocalisations of the great spotted kiwi (A. haastii), the largest of the Apteryx species. Acoustic recorders were installed near the breeding den sites of 7 great spotted kiwi pairs residing in Hawdon Valley, Canterbury between November 2012 and March 2013. A total of 133 whistle vocalisations from 10 individuals were subject to detailed temporal and spectral analysis. Male and female syllables were found to be sexually dimorphic; syllables in male calls tended to be longer and more highly pitched than their female counterparts. Despite this dimorphism, patterns of intra-call variation were consistent between the sexes. It appears that intra-call variation is a trait which varies markedly within the Apteryx genus.
Prior to 1992 the total population of New Zealand king shag (Leucocarbo carunculatus) was estimated to be about 300 individuals. Between 1992 and 2002, colonies in the outer Marlborough Sounds, New Zealand were surveyed by boat and the total population was estimated to be 645 birds. About 92% of all birds occurred at Duffers Reef, North Trio Island, Sentinel Rock, and White Rocks, with an estimated 102-126 breeding pairs. A survey in February 2015 was the first to be conducted from the air. All colonies were photographed within 44 minutes prior to the morning departure and the total population was estimated to be 839 individuals. A total of 187 pairs/nests were recorded using aerial 3D images of all breeding colonies in June 2015. North Trio Island was the largest breeding colony with 33.7% of all nests, followed by Duffers Reef with 18.7% of all nests. Despite the larger revised population size, the species remains Nationally Endangered.
The white-flippered penguin (Eudyptula minor albosignata) population on Banks Peninsula, New Zealand, was extensively preyed on by mammalian predators during the 1980s and 1990s with the loss of many colonies and the reduction in size of others. This paper presents the results of a 20-year study designed to identify the predators primarily responsible for these losses. It was based on the monitoring of 9 colonies ranging in size from 2 to 37 nests on a 1.7 km section of rocky coastline. Predators were trapped in the largest colony to determine the species present and their relevant behaviour. The other colonies were left unprotected, 6 of which were accessible to predators and 2 were not. Predation of penguins was first observed in the area in 1981 and it occurred annually through to the end of the study in 1995. Five of the 6 unprotected colonies were lost in 1982 and 1983 while the inaccessible colonies were unaffected. The remains of penguins that had been preyed on were found in the ‘protected’ colony in 11 of the 15 years between 1981 and 1995. These had been taken during the second half of the moulting season in February, and during the non-breeding season from April to August. No predation was observed during September to January when the penguins were breeding. A total of 47 mustelids were trapped in the ‘protected’ colony of which 43 (91%) were ferrets (Mustela furo). Overall there were 16 instances of predation that could be attributed to ferrets and 1 that was attributed to a ferret although the predator was not caught. The onset and sustained period of penguin predation by ferrets followed an eruption in their numbers Banks Peninsula-wide. This was most likely triggered by a corresponding increase in the numbers of rabbits (Oryctolagus c. cuniculus), their primary prey.
The southern black-backed gull (Larus dominicanus) is a common species throughout New Zealand, and has a significant presence in Auckland City. Large colonies are present on Rangitoto Island only 8 km from the city’s centre. The proximity of these colonies to the anthropogenic resources of the city may have influenced breeding locations and local populations. Using field data from the 2012/13 breeding period, we compare the current status of the breeding population on Rangitoto Island with historical data collated from literature. The Rangitoto population exhibited rapid growth throughout the early 20th century, a pattern attributed to environmental changes associated with European settlement and development. Since the 1980s, the colony sizes have declined, a change that is consistent with other gull populations both nationally and globally. The driver of the population changes is likely to be the availability of food and the expansion of vegetation into the colonies. Human disturbance and predation are discounted as impacting on population change.