Publications Archive

Holdaway, R.N.; Allentoft, M. E. 2022. A basic statistical approach to determining adult sex ratios of moa (Aves: Dinornithiformes) from sample series, with potential regional and depositional biases. Notornis 69: 158-173.

Abstract: Procellariiform seabirds are vulnerable to numerous threats, including the growing issue of urban light pollution. Seabirds that are found grounded are often treated by avian/wildlife rehabilitation centres, but approximately 30% do not survive. Here, we necropsied 19 grounded Cook’s petrels (tītī, Pterodroma cookii) that did not survive and report the cause of death and injuries. We also investigate potential risk factors, including association with light pollution, seabird sex, age, and sensory features. We found that a 70% of Cook’s petrels had head trauma, internal bleeding, and/or wounds as the main causes of death (p > 0.05). These injuries are consistent with collisions, likely due to disorientation from light pollution. Most Cook’s petrels were not stressed or in poor body condition, suggesting Cook’s petrels are typically healthy before being affected by lights. In the sample of Cook’s petrels studied, mortality was significantly biased towards young and male seabirds. Despite this apparent sex difference in collision risk, there was no detectable sex difference in measured sensory features, e.g. males did not have significantly larger eyes than females. The potential sex bias in death suggests male seabirds could be more vulnerable to light pollution, which warrants further research. Further research is also required to determine whether individual differences in sensory features relate to grounding risk, as our study only included a subset of dead seabirds. We also recommend that all grounded seabirds are taken to rehabilitation centres rather than released immediately.

Abstract: The current Buller’s albatross taxa (Thalassarche bulleri bulleri [southern] and T. b. platei [northern]) engage in transpacific migrations from breeding sites on New Zealand offshore islands to non-breeding areas in the south-eastern Pacific Ocean. Both taxa are identifiable from a combination of plumage colour features in the head and bill that are easy to detect at short distance (<15 m). There is also breeding allopatry between the taxa, with the onset of breeding 2.5 months earlier in the ‘northern taxon’. In this study, close-range sightings and captures of lured Buller ́s albatross individuals off southern Perú were carried out during two pelagic trips in May–July 2021 onboard a small- scale longline fishery wooden boat (12 m long), during their normal operations when targeting sharks. We report on the presence of 41 Buller ́s albatross, of which 40 were recognized as ‘northern taxon’ and one as ‘southern taxon’. The great majority of the ‘northern taxon’ were adults (92.5%), with the remaining identified as sub-adults (7.5%). Birds were sighted between 126 and 223 km offshore west-south-west from the port of Ilo, Perú (17°38.64 ́S, 71°20.77 ́W). Birds sighted were preferentially in oceanic areas above the abyssal plain (68% of sightings), with a mean depth of 4,537 m, demonstrating that the ‘northern taxon’ is a truly oceanic species. No birds were observed by us over the continental shelf. Discrimination of ‘northern taxon’ from ‘southern taxon’ is possible from a combination of the plumage colour features in the head and bill. However, identification and comparison of photographs for both taxa taken at sea can be problematic, due to varying light conditions, unless the birds can be drawn close to the photographer using attractants, such as offal discards.