Phase 3 of the rodent-eradication programme on South Georgia (Islas Georgias del Sur)* in the South Atlantic, last reported in ACAP Latest News to be 80% completed by the South Georgia Heritage Trust’s “Team Rat” (click here), reached 100% coverage two days ago on Monday the 23rd as reported in Project News No. 26.

"At 12:37 today I watched helicopter Alpha Mike flown by Chief Pilot Peter Garden pick up the 259th load of Phase 3 rodent bait and then disappear over the hill. Thirteen minutes later Peter returned with an empty bucket, as he has done many, many times before. But this load was different, because it was the last load of the Charlotte baiting zone, and the last load of Phase 3. Not only that, but this was also the last load of bait for the entire South Georgia Habitat Restoration project. After many years of preparation, three seasons of fieldwork, more than 800 bait loads, a thousand helicopter flying hours and over a thousand square kilometres treated, the final pellet had been dropped."

Now that Phase 3 is completed and thus all the areas of the island infested with either Norway or Brown Rats Rattus norvegicus or House Mice Mus musculus have been treated with poison bait comes a long (and no doubt anxious) wait for at least two years with no further signs of live rodents before the island can be declared officially rat (and mouse) free.  If this is achieved then South Georgia (Islas Georgias del Sur)* will become the largest island by far anywhere in the World where rodents have been eradicated; allowing its especially smaller seabirds a chance to recover.  Success should encourage plans and efforts to remove rodents from other ACAP-listed seabird islands in the Southern Ocean.

Transferring poison bait from ship to shore, photograph courtesy of Tony Martin

Click here to access Project News, Team Rat’s monthly newsletter.

Other news from the island is that following the last account (click here) on the demise of Reindeer Rangifer tarandus on South Georgia (Islas Georgias del Sur)* which had 44 animals removed in January this year, a further three animals (all males) were spotted in February, as reported below.

“Three male reindeer were spotted on February 14th by a field party and one of the helicopters baiting the Barff Peninsula to remove rats.  The Barff Peninsula was largely cleared of introduced reindeer last summer, with a further ‘mopping up’ operation carried out by the same Norwegian SNO marksmen earlier this season.   Although the reindeer were skittish around the helicopter, once baiting operations had moved to the south the hunting party of three managed to get close enough to shoot the reindeer.  It was notable that the three reindeer were in very good condition; heavy with big racks of antlers.  Previously, with thousands of deer in the area, it was so overpopulated that the animals were small and in poor condition” (click here).

Now gone: a Reindeer among King Penguins, photograph by Martin Collins

John Cooper, ACAP Information Officer, 25 March 2015

*A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands (Islas Malvinas), South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur) and the surrounding maritime areas.

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