Kalinka Rexer-Huber

Low burrow occupancy and breeding success of burrowing petrels at Gough Island: a consequence of mouse predation

The predatory behaviour of introduced house mice Mus musculus at Gough Island is known to impact on albatross and petrels, resulting in the Tristan Albatross Diomedea dabbenena and Atlantic Petrel Pterodroma incerta being listed as “Critically Endangered” and “Endangered”, respectively. Although predation has been documented for two burrowing petrels and one albatross species, the impact of house mice on other burrowing petrels on Gough Island is unknown. We report burrow occupancy and breeding success of Atlantic Petrels, Soft-plumaged Petrels Pterodroma mollis , Broad-billed Prions Pachyptila vittata , Grey Petrels Procellaria cinerea and Great Shearwaters Puffinus gravis . With the exception of the Great Shearwater, breeding parameters of burrowing petrels at Gough Island were very poor, with low burrow occupancy (range 4–42%) and low breeding success (0–44%) for four species, and high rates of chick mortality in Atlantic Petrel burrows. Breeding success decreased with mass, suggesting that smaller species are hardest hit, and winter-breeding species had lower breeding success than summer breeders. The results indicate that introduced house mice are having a detrimental impact on a wider range of species than previously recorded and are likely to be causing population declines among most burrowing petrels on Gough Island. The very low values of burrow occupancy recorded for Soft-plumaged Petrels and Broad-billed Prions and greatly reduced abundance of burrowing petrels in comparison to earlier decades indicate that Gough Island’s formerly abundant petrel populations are greatly threatened by the impact of predatory house mice which can only be halted by the eradication of this species from the island.

Winter diet of striated caracara Phalcoboenus australis (Aves, Polyborinae) at a farm settlement on the Falkland Islands

Striated caracaras occur only on the Falkland Islands and the outer islands of southern Chile and Argentina. In summer, the species associates with seabirds and seals and depends heavily upon them for food. The winter diet is less well understood. We studied the diet of 90–130 mainly juvenile and sub-adult striated caracaras overwintering at a farm on Saunders Island, Falkland Islands, in mid-winter (July–August) 2011. Direct observations of feeding and regurgitation pellets collected at a roost indicate that the winter diet of the striated caracaras at the site is mainly native geese, beetles and other invertebrates, and the carcasses of domestic sheep. This study illustrates seasonal shifts in the diet of this near-threatened South Atlantic endemic and suggests an important nutritional link between juvenile and subadult caracara survival in winter and traditional human activities at sheep farms.

Kerguelen petrel ( Lugensa brevirostris ): a ‘new’ breeding species for South Georgia

Short Note Kerguelen petrel (Lugensa brevirostris): a ‘new’ breeding species for South Georgia ANDY BLACK, GRAHAM PARKER, KALINKA REXER-HUBER, ERICA SOMMER and RICHARD J. CUTHBERT Government of South Georgia and the South Sandwich Islands, Government House, Stanley, Falkland Islands, FIQQ 1ZZ Falkland Islands Fisheries Department, PO Box 598, Stanley, Falkland Islands, FIQQ 1ZZ Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, SG19 2DL, UK seabirds@gov.gs

Ringing injuries in the Gough Moorhen Gallinula comeri

To examine the extent and possible causes of ringing injuries in the Gough Moorhen Gallinula comeri, ringed birds were monitored and recaptured. Of ringed Gough Moorhens, 12.5% developed injuries associated with leg rings. Injuries developed rapidly, ranging from lameness to complete crippling of the leg. Given the cryptic behaviour of Gough Moorhens and the rapid onset of injuries, long-term use of metal rings is not recommended for free-roaming Gough Moorhens. Ringing injuries have not been reported previously in rails, highlighting the need for caution when ringing previously unstudied bird species.

Morphometric and genetic sexing in the Gough Moorhen Gallinula comeri

To develop an accurate, low-cost method for sexing Gough Moorhens Gallinula comeri using morphometric measurements, twelve measurements were taken from 59 birds and validated against genetic sexing. The classification accuracy of variables was determined and discriminant analysis was used to test whether multiple variables improved accuracy. Males were larger than females in all dimensions. Head length reliably differentiated male and female Gough Moorhens. A threshold of 64 mm correctly classified 92% of the sample birds; adding other variables did not improve accuracy. Gough Moorhens can be sexed with an acceptable level of accuracy using a single morphometric variable, but genetic sexing is needed to confirm the sex of individuals that fall within the overlap zone (62–66 mm).

Grey petrel population on Campbell Island 14 years after rodent eradication

Abstract Populations of grey petrels have declined globally due to both incidental capture in commercial fisheries and predation by introduced mammals at breeding sites. In the New Zealand region, grey petrels only breed on Campbell and Antipodes islands. Rats were successfully eradicated from Campbell Island in 2001. We assessed the spatial extent and conducted the first quantitative population estimate of the grey petrel population on Campbell Island and surrounding islets. There was an estimated c. 96 pairs (95% CI: 83, 109) of breeding grey petrels from the four colonies. Since work was conducted during the middle of the chick-rearing stage, this is an underestimate of the breeding population. The Campbell Island grey petrel breeding population remains small. Our study provides a baseline for future population estimates of grey petrels on Campbell Island.