Satellite telemetry can provide unique information on the biology and behaviour of mobile animals such as albatrosses. Determining areas of concentrated activity, essential resources and time-related changes in range use is of great importance for theoretical biology, practical conservation, and fisheries management. Utilisation Distributions (UDs), from a probabilistic model of the relative time spent by an animal in an area, were prepared using a kernel function in a Geographical Information System. Properties of the model were investigated, using satellite-tracking data from six northern royal albatrosses (Diomedea sanfordi) during eight over-wintering visits to seas off South America. We analysed UD areas and shape for different settings of the kernel smoothing parameter, a variety of location subsets associated with different sample sizes, sampling time periods and telemetry regimes. Small samples and intermittent transmission regimes reduced the UD range area. Individual bird data sets were combined to give comparable UDs. The UD model may help comparison of range areas and the identification of resource use, but they cannot identify an activity without additional information. For pelagic seabirds, UD preparation and interpretation require judgement and care.
Accounts of magpie Gymnorhina tibicen attacks on birds in New Zealand were collated from literature and a survey of the public, and then summarised to identify the frequency and characteristics of reported attacks on different species. Magpies were reported attacking 45 bird species. Species commonly found in rural habitats (e.g., harrier hawk Circus approximans, blackbird Turdus merula) where magpies are abundant were attacked most; however, a directly proportional relationship between species abundance in rural habitats and reported attack frequency did not occur. Species consuming similar foods to magpie tended to be attacked more often, probably because these foods are more abundant in rural areas. Attacks on smaller birds (e.g., grey warbler Gerygone igata) regularly (66%) resulted in death, but deaths declined as victim weight increased. Non-contact attacks were most common for the largest species (e.g., kereru Hemiphaga novaeseelandiae). Non-contact and non-lethal contact attacks occurred throughout the year while attacks resulting in death occurred mainly during the magpie’s breeding season (July to November). This study indicates that magpies can attack a wide range of species but fails to determine why (no one explanation satisfies all cases). Limitations of the dataset and future research to control these are discussed.
We analysed 13C and 15N isotopic enrichment in Australasian harrier (Circus approximans) eggshell and two discarded harrier feathers from Motunau Island, a regionally important seabird breeding island. Among the prey remains found at the nest was a prion (Pachyptila sp.) wing fragment and a predated blue penguin (Eudyptula minor). We combined isotope data from the prey remains, plus potential prey items obtained from the mainland, to reconstruct harrier diet and evaluate incorporation of seabird nutrients. During egg material formation, blue penguins made up a major part of the female harrier’s diet. During autumn, when feathers were re-growing, the two feathers (which may or may not have been from different individuals) gave very different results. The feather with the more marine signature was growing when harrier diet included a significant proportion of blue penguin and/or fairy prion (Pachyptila turtur) material. Formation of the other feather may have occurred while harrier diet was primarily terrestrial. Our results are indicative of the usefulness of stable isotopic analysis in elucidating nutrient flows and contributions to animal diet.
A survey was undertaken in the Te Waiiti Stream, Bay of Plenty, in summer 2002/2003, to identify blue duck (Hymenolaimus malacorhynchos) roost habitat. Thirty-six roosts were identified along 18.5 km of stream channel, averaging three roosts per blue duck pair. Stable undercut banks were most commonly used as roost sites (42%), followed by log jams along stream banks (25%). Large woody debris (LWD) was a component of 50% of the roost sites, and there was a positive relationship between LWD loadings in the stream channel and number of LWD roosts. All roosts provided overhead and lateral cover, most likely an adaptive response to current and historic avian predators, and all were located at the water’s edge. The location and composition of roosts provided easy access to the stream channel, discrete cover for rearing juveniles and for moulting, and daytime shelter. There were indications that channel morphology characteristics in the lower section of the survey reach may be limiting roost habitat availability and blue duck occupancy. Suitable roost habitat is a year-round requirement for blue duck and should be considered when evaluating their habitat.
We describe and name a new subspecies of fulmar prion as Pachyptila crassirostris flemingi. This little-known seabird has less than 1,000 pairs breeding at the Auckland Islands and 1,000-10,000 pairs breeding on Heard Island. It is probably largely sedentary around these islands in winter, with possible stragglers reaching mainland New Zealand and Tasmania.
A previously unknown Moriori-based account of the extinct Hawkins’ rail (Diaphorapteryx hawkinsi) from the Chatham Islands is presented and discussed. The account, recorded by Sigvard Jacob Dannefaerd in a letter to Lord Lionel Walter Rothschild in 1895, includes details of the species’ appearance, behaviour and Moriori hunting methods. A second, similar description of a previously unidentified Chatham Islands bird is also linked to Hawkins’ rail. The clarity of the accounts suggests a considerably later extinction date for the species than previously supposed.
The diet of blue penguins (Eudyptula minor) at Oamaru, New Zealand was examined by stomach flushing. The 22 species identified comprised 14 fishes, 1 cephalopod and 7 crustaceans. Slender sprat (Sprattus antipodum) accounted for more than half of the diet throughout most of the year while Graham’s gudgeon (Grahamichthys radiata) and arrow squid (Nototodarus sloanii) were also important seasonally. Prey were either small, schooling, nearshore species or pelagic juveniles of larger species.