Biometric studies of short-tailed shearwaters (Puffinus tenuirostris) indicate differences in body mass and linear measurements between sexes. Here the degree of sexual size dimorphism in 390 short-tailed shearwater adults is assessed and a sex-discriminating function is produced to improve methods for sexing live birds in the field. Analysis of body mass and linear measurements showed males to be significantly heavier and larger than female birds in all variables. The largest degree of sexual size dimorphism was in bill depth (7.5%) followed by body mass (5.1%). Bill depth plus total head length were the most accurate variables in a discriminant function model. Together, these 2 variables predicted sex with 84% accuracy. Bill depth alone predicted sex with 82% accuracy. However, application of a sex-discriminating model developed from another colony, did not correctly classify the sex of adult birds as accurately. This can be explained by the existence of significant geographical variation in body size within the species and reinforces the need for colony-specific sex discriminant models. Comparisons within-pairs revealed that bill depth is a more reliable indicator of sex, without the need for a discriminant function analysis. Contrary to previous studies, measurements of male and female partners showed no evidence of assortative mating in any character assessed. If short-tailed shearwaters mate assortatively then it may be based on traits other than structural size.
Stable isotopic (δ13C; δ15N) analysis of bone collagen and other refractory biological materials is a mainstay of palaeoecological research, but comparability between individuals depends on homogeneity within the sample specimens. Long bones of extinct New Zealand moa display lines of arrested growth that reflect prolonged development over several years, leading to potential systematic inhomogeneity in stable isotopic enrichment within the bone. We tested whether the isotopic content within a Euryapteryx curtus tibiotarsus is homogeneous by measuring δ15N and δ13C values in 6 adjacent 1cm-diameter cortical bone cores arranged along the bone axis from each of the proximal and distal ends. We then measured isotopic ratios in 5 radial slices of a core from the mid-shaft of a Pachyornis elephantopus tibiotarsus to see if there was any depth (ontogenetic) effect at a single sampling point. The δ13C value increased with distance from the proximal bone end, but neither δ13C nor δ15N values in samples from the distal end of the bone were correlated with position. Within mid-shaft cortical bone, the δ13C value decreased with depth but δ15N values were constant. Sampling the entire depth of cortical bone from the caudal surface at the distal end of the tibiotarsus, if feasible, therefore provides a spatially homogenous material, free of maturation effects on stable isotopic composition. If for any reason that position cannot be sampled, the outer (radial) layer at the mid-shaft can be substituted.
An annotated checklist of the birds of Motu Kaikoura (Selwyn Island) in the Hauraki Gulf, New Zealand, is provided from surveys carried out between Dec 2006 and Jun 2008, supplemented by other recent observations. Thirty-seven species were recorded, including 25 species of land or wetland birds, and 12 species of seabirds and shorebirds. A total of 26 species were indigenous and 11 species were exotic. Motu Kaikoura was gazetted as a scenic reserve in 2004, with ecological restoration a key aim of its management. The 564 ha island has low vegetation diversity, reflecting a long history of anthropogenic degradation. Fallow deer (Dama dama), rats (Rattus spp.), mice (Mus musculus) and feral cats (Felis catus) were present on the island.
Eradication of invasive mammals has been a management priority, with the bird surveys representing baseline data against which the progress of ecological restoration can be measured.
Here I report on a small scale study aimed at generating baseline information on the immune response of wild red-fronted parakeets, as assessed by blood cell counts, and subcutaneous challenge with phytohaemagglutinin (PHA), a mitogen that causes swelling at the point of injection. Eleven parakeets captured in mist-nets were injected into the right patagium with 0.5 mg PHA and the resulting swelling measured at 6 hours post-injection. Prior to PHA challenge, feather and blood samples were collected for detection of beak and feather disease virus and Plasmodium. Blood smears were also prepared for blood cell counts. Swelling occurred 6 hours post-injection in all but one individual, which tested positive for beak and feather disease virus. In this individual, no measurable swelling was detected. Estimated leucocyte counts, lymphocyte counts and heterophil counts of the same individual were similar to values of beak and feather disease virus negative individuals. Plasmodium DNA was detected in 2 individuals and their immune response was similar to that of parakeets testing negative for both beak and feather disease virus and Plasmodium. Estimated leucocyte counts, lymphocyte and heterophil counts did not differ between Plasmodium infected and non-infected individuals. The fact that the only individual testing positive for beak and feather disease virus showed no immune response to PHA challenge suggests increased susceptibility to other pathogenic infections. Although preliminary, this study highlights the potential damaging consequences of the accidental introduction of beak and feather disease virus in conservation programmes of threatened New Zealand parrots, some of which might already suffer from decreased immunocompetence resulting from reduced genetic diversity.
The introductions of mallard (Anas platyrhynchos) to New Zealand, and their breeding and release as a game bird by Acclimatisation Societies are summarised. We identify 19 importations, 14 of which (a total of 115 birds all from Great Britain) were sufficient to establish small feral populations in southern and central New Zealand by about 1910. Five subsequent importations were made by Aucklander C.A. Whitney, 3 from Great Britain in 1910 (6 birds), 1914 (number unconfirmed) and 1927 (393 birds), followed by 99 birds (1937) and 45 eggs (1941) both from the USA. It was Whitney’s distribution of eggs following his initial USA importation that prompted widespread breeding and release programmes which, in some regions, extended into the 1960’s and 70’s. We identify a minimum of 30,000 mallards having been released by Acclimatisation Societies, but numerous releases by private individuals remain unrecorded. Almost all regional Acclimatisation Societies at some time released mallards into the wild.
New bioacoustic technologies offer novel ways to monitor bird populations in the field. Bioacoustic techniques can greatly enhance effective field time, enhance survey site coverage, and increase quantification of key time periods such as crepuscular and nocturnal hours. Moreover, digital files provide searchable, independently verifiable records. Historical impediments to the use of bioacoustics have diminished with unit costs declining and data storage capacities increasing. Recent software developments enable rapid extraction of targeted bird calls and facilitate ease of data analysis. This paper details the recent application of bioacoustic technology at a proposed wind farm site in the upper North I, New Zealand. In this case, bioacoustics were employed as a supplement to on-site field observations and as a complement to avian radar technology. Results illustrate the utility of bioacoustic methods, highlighting the range and scale of potential data outputs. In addition to the detection of flight calls and song, audible wing flap noise may provide a further means of identification for some species. Targeted monitoring of migrant birds, cryptic marshbirds, and rare seabirds are identified as potential future applications.
One-legged standing (or unipedal posture) in birds was investigated with a particular focus on the role of ambient air temperature on this behaviour in a variety of wading birds and waterfowl. Waterfowl (Anas platyrhynchos and Cygnus atratus) were less likely to be observed standing on 1 leg than long-legged species of wading birds (Ardea novaehollandiae, Limosa lapponica, Platalea regia, Himantopus himantopus), perhaps because of differences in the length of their legs. Feeding behaviour and activities associated with disturbance influenced the frequency of unipedal posture. For captive flamingos (Phoenicopterus roseus) and pied stilts (Himantopus himantopus) the proportion of birds observed standing on 1 leg increased as the temperature increased from 8 to 19C. This observation contradicts the theory that unipedal posture is a behavioural adaptation to minimise heat loss on cold days. An alternative theory based on unihemispheric slow wave sleep (USWS) patterns is proposed as an explanation for unipedal posture and is recommended as a focus for future research. Our results also confirm the importance of considering differences between species in leg anatomy and activity levels to measure the effects of temperature.