Publications Archive

Ten white-headed petrels (Pterodroma lessonii) from Adams Island, Auckland Islands, were tracked during 2011–14 using miniature geolocators, in the first study to examine the at-sea movements and key foraging areas of this pelagic seabird. Data revealed extensive migrations west to South Africa and east into the central South Pacific Ocean. The birds returned to colonies Aug–Oct. Median departure on pre-laying exodus was 24 Sep. Birds were away for up to 77 days during pre-laying and moved west towards the Indian Ocean. Laying occurred 24 Nov–10 Dec. The first major incubation shifts by males and females were c. 19 days in duration. The maximum foraging range during incubation was 5,230 km from the colony, the most distant recorded by any seabird during this breeding stage. After eggs hatched in January, some birds foraged off Antarctica in sea temperatures down to –1°C. Birds spent the inter-breeding period in disjunct areas (off South Africa, south of Australia, Tasman Sea, and South Pacific Ocean). This study revealed an unusual courtship behaviour not recorded previously in other seabird species. Females returned from distant oceans to spend just a few days ashore in the pre-laying period before leaving the breeding site until the following spring. The males also skipped breeding at the same time as their mates, but returned earlier in the season. The new knowledge gained about the breeding activity of this species will assist with future population assessments.

Adams Island (9,693 ha) is the second-largest island in the Auckland Islands group, and the largest island in New Zealand on which introduced mammals have never become established. Adams Island is forested on the northern sheltered parts of its coastline, and has shrubland, grassland, and fellfield at higher altitudes, and herb-field in fertile open sites. Sheer cliffs dominate the exposed, southern side of the island, and above them, narrow shelves support lush herb-fields. This diversity of habitat in close proximity supports unique communities of birds, with most species in remarkable abundance due to the absence of introduced predators. With the notable exception of the Auckland Island merganser (Mergus australis), the island’s birdlife is close to what it would have been in pre-human times, and includes high densities of species that are now rare or missing on nearby Auckland Island. This paper describes the island, the history of ornithological exploration, and the past and current state of the avifauna. The 48 extant bird species recorded from the island comprise 22 land birds and 26 seabirds, of which 34 species (16 land birds and 18 seabirds) have been recorded breeding or are likely to be breeding there. Eight species introduced to New Zealand have also made their way to Adams Island, and six probably breed there.

The wrybill (Anarhynchus frontalis) is an endemic plover that breeds only in braided rivers east of the main divide in the South Island of New Zealand. It is threatened by a range of factors, including loss and degradation of habitat, flooding, and predation. We monitored wrybills in 2 sites in the Tekapo River and 2 in the Tasman River in the Mackenzie Basin, South Canterbury, during 3 breeding seasons (1997/98–1999/2000). We aimed to compare survival and productivity between areas with and without trapping (mammalian predator control) to determine whether predator control was associated with higher survival and/or breeding success of wrybills. In the Tekapo River, results were similar between trapped and un-trapped areas, suggesting that control had little effect. In the Tasman River, there were large differences between the two sites and trapping appeared to be beneficial; in the upper river (un-trapped), productivity and survival were very low and in the lower (trapped) site they were high. Over the whole study, 67.3% of nests hatched, and depredation was the largest cause of nest failure. Fledging success (the proportion of chicks hatched that fledged) averaged 35.4%. Losses at the chick stage were higher than at the egg stage, and there was only a weak correlation between nesting success and overall breeding success; we therefore caution against the use of nesting success as a proxy for overall breeding success. Productivity averaged 0.49 chicks fledged per pair over the whole study; when the very low values from the upper Tasman site were excluded, productivity averaged 0.61. Survival of adult male wrybills was lower than survival of females in all four study sites. Measurement of adult survival is important in determining the full effect of predator control (and in determining population trends) but is often overlooked. At the time of our study, wrybill populations in 3 of our 4 study sites appeared not to be self-sustaining and, in the absence of immigration, were in decline. A number of factors, including depredation by mammals, can affect breeding success. Trapping may be beneficial, but temporal and geographic differences in predator densities, as well as variability in other threats (such as flooding and levels of avian predation) mean that predicting when and where mammalian predator control may benefit wrybills is currently difficult.