Grant Harper (Biodiversity Restoration Specialists, St Arnaud, New Zealand) and Nancy Bunbury have published a review paper in the open-access journal Global Ecology and Conservation on the biology and impacts of three species of introduced rats Rattus spp. on tropical islands.  The paper identifies 10 species of procellariiform seabirds, mainly gadfly petrels Pterodroma spp. and shearwaters Puffinus spp., but also including Black-footed Phoebastria nigripes and Laysan P. immutabilis Albatrosses, as impacted.

No storm petrels Oceanitidae are listed in the review despite their presence on some islands considered tropical in the review (e.g. Tristram’s Storm Petrel Oceanodroma tristrami on French Frigate Shoals, Kure Atoll and Laysan Island in the North Pacific), perhaps because of the paucity of studies.

The paper’s abstract follows:

“The three most invasive rat species, black or ship rat Rattus rattus, brown or Norway rats, R. norvegicus and Pacific rat, R. exulans have been incrementally introduced to islands as humans have explored the world’s oceans.  They have caused serious deleterious effects through predation and competition, and extinction of many species on tropical islands, many of which are biodiversity hotspots.  All three rat species are found in virtually all habitat types, including mangrove and arid shrub land.  Black rats tend to dominate the literature but despite this the population biology of invasive rats, particularly Norway rats, is poorly researched on tropical islands.  Pacific rats can often exceed population densities of well over 100 rats ha⁻¹and black rats can attain densities of 119 rats ha⁻¹, which is much higher than recorded on most temperate islands.  High densities are possibly due to high recruitment of young although the data to support this are limited.  The generally aseasonally warm climate can lead to year-round breeding but can be restricted by either density-dependent effects interacting with resource constraints often due to aridity.  Apparent adverse impacts on birds have been well recorded and almost all tropical seabirds and land birds can be affected by rats.  On the Pacific islands, black rats have added to declines and extinctions of land birds caused initially by Pacific rats.  Rats have likely caused unrecorded extinctions of native species on tropical islands.  Further research required on invasive rats on tropical islands includes the drivers of population growth and carrying capacities that result in high densities and how these differ to temperate islands, habitat use of rats in tropical vegetation types and interactions with other tropical species, particularly the reptiles and invertebrates, including crustaceans.”

Black-footed and Laysan Albatrosses, photograph by Pete Leary

References:

Harper, G.A. & Bunbury, N. 2015.  Invasive rats on tropical islands: their population biology and impacts on native species.  Global Ecology and Conservation 3: 607-627.

McClelland, G.T.W., Jones, I.L., Lavers, J.L. & Sato, F. 2008.  Breeding biology of Tristram's Storm-petrelOceanodroma tristrami at French Frigate Shoals and Laysan Island, Northwest Hawaiian Islands.  Marine Ornithology 36: 175-181.

John Cooper, ACAP Information Officer, 24 March 2015

Over 180 Endangered Hutton's Puffinus huttoni Shearwater fledglings downed by bright lights have been rescued from roads in and around Kaikoura on New Zealand’s South Island so far this breeding season.  Following capture the young birds are measured, weighed, banded and released to sea.  The fledglings leave their two mountain colonies in the Seaward Kaikoura Range inland of Kaikoura and head towards the ocean but can become attracted to the town's street lights.

Banded fledgling

Lindsay Rowe of the Hutton's Shearwater Charitable Trust said they were flying down from the mountains and ended up on roads or in gardens.  "That's the most we've found for seven or eight years," Rowe said. "We picked up 45 last year, so we've done a lot more already.  The wind may have been a factor, getting exhausted battling the southerly."

Catch and release

Last year, a banded shearwater fledgling showed up six days later on the New South Wales coast of Australia, near Sydney.  Research on Hutton's Shearwaters fitted with geo-locators has revealed details of their winter migration to Australian waters, with birds either completing a clockwise or anti-clockwise circuit of that continent.  Young birds remain in Australian waters for 4-5 years before returning to breeding colonies in the Seaward Kaikoura Range.

Della Bennet of the University of Canterbury’s Department of Biological Sciences is undertaking MSc research into the foraging areas and behaviour of Hutton’s Shearwaters from the translocated Kaikoura Peninsula/Te Rae o Atiu colony as described below.

Understanding seabird diet is vital for conservation management, as food availability is dependent on environmental conditions that can affect the temporal and spatial distribution of prey species and in turn affect breeding and chick rearing.  These conditions can lead to a mismatch in resources and cause low growth rates, low fledging success and high chick mortality.  To date, very little is known about the diet of the Hutton’s shearwater, with previous studies based only on the gut content of dead carcasses.

Monitoring loggers (depth, temperature, wet/dry and time) will assess the daily foraging behaviour of Hutton’s shearwater adults from the Kaikoura Peninsula colony.  These loggers will allow the construction of an accurate activity budget and maximum diving depth.  The data collected by the loggers will be integrated with stable isotope analysis of the bird’s feathers and the Kaikoura nearshore food-web (fish and plankton) to investigate the birds’ diet.”

The above information and photographs are taken from recent postings to the Hutton's Shearwater Charitable Trust’s Facebook Page

Click here for a media report of the downed fledglings.

John Cooper, ACAP Information Officer, 23 March 2015

Bungo Nishizawa (Graduate School of Fisheries Sciences, Hokkaido University, Japan) and colleagues write in the journal Marine Biology on the at-sea distributions of Black-footed Phoebastria nigripes and Laysan P. immutabilis Albatrosses deduced from ship-based surveys in the North Pacific Transition Zone during the non-breeding season.

The paper’s abstract follows:

“The North Pacific Transition Zone (NPTZ) is one of the most productive offshore regions.  To identify important habitats for pelagic top predators within this region, we investigated the at-sea distributions of black-footed (Phoebastria nigripes) and Laysan albatrosses (P. immutabilis) by vessel-based surveys during their non-breeding season (July and October in 2010 and September and October in 2011).  We developed statistical models using satellite-based oceanographic data at spatial scales of 4, 20 and 80 km to explain their densities.  For both species, sea surface temperatures (SST) and distance to the Emperor Seamounts emerged as important factors in the better-fitting models at all spatial scales.  In addition, black-footed albatrosses were widely distributed in the NPTZ (SST17.7–27.4 °C), whereas Laysan albatrosses favoured northern and colder waters (13.6–25.4 °C).  Our results also indicated that the Emperor Seamounts, where trawling and longline fishing occur, were an important habitat for both species in the NPTZ.  Therefore, careful attention should be paid to interactions between fisheries and albatross species in this region”

Black-footed and Laysan Albatrosses, photograph by the Kure Atoll Conservancy

Reference:

Nishizawa, B., Ochi, D., Minami, H., Yokawa, K., Saitoh, S.-I. & Watanuki, Y. 2015.  Habitats of two albatross species during the non-breeding season in the North Pacific Transition Zone.  Marine Biology 162: 743-752.

John Cooper, ACAP Information Officer, 22 March 2015

Jean-Baptiste Thiebot (Centre d’Études Biologiques de Chizé, Villiers-en-bois, France) and colleagues have written in the journal Polar Biology on the curious case of recapturing an albatross at its Amsterdam Island breeding site with a message added to its leg by a longliner at sea.

The paper’s abstract follows:

“Commercial fisheries currently pose a serious threat at sea to the conservation of a number of pelagic seabirds.  However, these interactions are complex, and reports on population-specific bycatch in the high seas are scarce.  Here we report the case of an Indian yellow-nosed albatross Thalassarche carteri re-sighted on Amsterdam Island after an apparent capture by an Indonesian long-liner, as indicated by a message attached to the bird.  This record demonstrates that Amsterdam birds may interact with long-liners indeed, at least during winter, and that such interactions are not systematically lethal.  We suggest that bycatch sub-lethal effects should be investigated at colonies with high risks of individual capture at sea.”

Indian Yellow-nosed Albatross, photograph by Peter Ryan

Reference:

Thiebot, J.-B., Demy, J., Marteau, C. & Weimerskirch, H. 2015.  The rime of the modern mariner: evidence for capture of yellow-nosed albatross from Amsterdam Island in Indian Ocean longline fisheries.  Polar Biology DOI 10.1007/s00300-015-1680-5.

John Cooper, ACAP Information Officer, 21 March 2015