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.
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.
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.
There have been few studies on the temporal patterns of social behaviours and how they relate to timing of life history stages in nocturnal colonial bird species. This study focuses on the threatened Westland petrel (Procellaria westlandica; Procellariidae), to investigate temporal patterns in colonial interactions, including vocalisations and social behaviours, in the context of petrel sociality. We conducted extensive behavioural observations on the colony at different time-scales (throughout single nights, between seasons, and across years) to characterise the temporal dynamics of at-colony behaviours. These analyses show consistent temporal variation in several behavioural attributes (e.g., social interactions, vocalisations, eyes closed, body movements), with little or no temporal variation in others (e.g., self maintenance or stationary behaviours). These data provide the basis for specific predictions to test the role of social interactions between temporally varying vocalisations and social behaviours in nocturnal colonial birds.
Monitoring of breeding success in 2006/07 and 2007/08, and visits in Dec 2007 to assess levels of stoat predation and burrow densities were undertaken in order to assess the status of Hutton’s shearwaters (Puffinus huttoni) at the 2 remaining breeding colonies. Long-term (20 year) estimates of burrow density within the Kowhai Valley show a consistent increase in burrow density within this colony. Along with the discovery of a new area of burrowed ground, these results suggest the population of Hutton’s shearwater has increased in this colony over the last 20 years. Burrow density data for Shearwater Stream are less robust, but does not appear to show a decline. Measures of predation rates in the Kowhai colony show no major differences in the numbers of adult shearwaters found on transects in comparison with the late 1990s and the recovery of shearwater carcasses from burrows in 2 recent seasons also does not differ from the late 1990s. Burrow occupancy levels in both colonies in 2006/07 are similar to the 1990s. In contrast, breeding success in both the Kowhai Valley and Shearwater Stream were very low in the 2006/07 and 2007/08 breeding seasons. Due to the lack of evidence suggesting an increase in stoat predation, these low values of breeding success are hypothesised to be a result of poor at-sea feeding conditions. The apparently consistent lower breeding success at the Shearwater Stream colony (and lack of evidence for alternative local environmental impacts such as heavy snowfall or rain events within this colony) may well be a consequence of stoats, due to the differential impact of stoats at this small colony (8,000 breeding pairs) in comparison to the far larger Kowhai Valley colony (106,000 pairs). Continued annual monitoring within both colonies and a programme of stoat trapping within the Shearwater Stream colony are recommended in order to better assess breeding success and to determine if trapping can protect the smaller colony. Five-yearly monitoring of burrow densities and predation rates should continue to help evaluate long-term trends and the health of this endemic New Zealand species.
In a 5 year radiotracking study of 55 falcons on the Wairau Plain, Marlborough, the causes of death in 21 birds were identified. Of these, 10 (47%) falcons were electrocuted (7 juvenile females, 1 adult female, 1 juvenile male, and 1 adult male). Seven of the 10 poles were fitted with transformers. This level of mortality is thought to be too high to sustain a population of falcons. Suggestions are made how to mitigate the problem.
Tree-cavity nesting is common for a broad range of bird species throughout the world. However, the majority of information on the use of cavity nests is largely derived from the Northern Hemisphere with little data originating from tropical or southern temperate areas. We discuss 3 factors (predation, microclimate, and cavity abundance) that may have shaped the evolution of New Zealand’s tree-cavity nesting birds. New Zealand’s landbird fauna possesses the highest percentage (24%) of secondary tree-cavity nesters (7 orders and 12 families) of any region examined. Given the high occurrence of tree-cavity nesting in New Zealand’s avifauna there may be environmental pressures that select for this form of nesting. Historically, birds were likely the main nest predators of New Zealand’s cavity nesting birds and indications are that nest predation levels are not comparable to some continental habitats. This suggests that other factors such as microclimate or cavity abundance may have played a disproportionate or complementary role in influencing the high percentage of tree-cavity nesting in New Zealand. However, evidence is limited and any attempt to identify selection pressures on tree-cavity nesting must be balanced against phylogenetic concerns, as some birds were likely tree-cavity nesters before their arrival in New Zealand.