A Northern Giant Petrel chick taking no notice of the drone 5 m above its head.  The silvery grey colour of the chick’s down, plus the characteristically large cleared area the chick has created round its nest mound makes nests easy to spot from the air (from the report)

In a final report to New Zealand’s Department of Conservation via its Conservation Services Programme (CSP), Graeme Elliot and Kath Walker (Albatross Research) describe the use of both foot searches and a drone to count the numbers of Northern Giant Petrel Macronectes halli chicks on Antipodes Island over two breeding seasons.  “The drone was usually flown high and fast towards suitable habitat, then it was dropped to about 20-30 m above the ground for slower scouting for nesting giant petrels. When a nest was spotted, the drone descended lower and a photo was taken of the nest from directly above it, which automatically recorded that nest’s grid reference.”

The report’s abstract follows:

“The number[s] of northern giant petrel chicks on Antipodes Island were counted just before they fledged during the summers of 2020-21 and 2021-22.  Counts were made on foot and through use of a drone.  The number of chicks in the two years was similar (194, 188) and using nesting success measures from Macquarie Island, estimates of the number of breeding pairs of 304 and 295 were made.  The number of northern giant petrels nesting on the island seems to have decreased and then increased since 1969 when they were first counted and this may be due to declines in the number of eastern rockhopper and erect-crested penguins nesting on the island, and an increase in the abundance of New Zealand fur seals.”

Reference:

Elliot, G. & Walker, K. 2022.  Numbers of Northern Giant Petrel breeding on Antipodes Island in 2021 and 2022.  Nelson: Albatross Research.  15 pp.

John Cooper, ACAP Information Officer, 05 August 2022

An Antipodean Albatross in flight. Photograph by Hannah Shand/Jordan

Kath Walker and Graeme Elliot (Albatross Research) have prepared a report, Antipodean wandering albatross satellite tracking and population study on Antipodes Island in 2021 and 2022, which has been made available by New Zealand’s Conservation Services Programme.

Results of the study indicate a number of factors involved in the population decline of Antipodean Albatrosses but emphasise female mortality as a key contributor, with interactions with pelagic surface long-line fisheries being the cause of death for a significant number of young females. The report also highlights the availability of numerous seabird bycatch mitigation measures which, if implemented by fisheries, would have a positive impact on population recovery.

Building on long-term population monitoring which has taken place regularly since 1994, the data gathered from the four-year satellite tracking and population study (2019 – 2022) have updated knowledge of the at-sea distribution of the Antipodean Albatross, as well as providing information on their biology.

The report's summary follows:

“The Antipodean wandering albatross Diomedea antipodensis antipodensis has been in decline since 2005. The decline appears to be driven in large part by high female mortality, though reduced breeding success and increased recruitment age have exacerbated the problem. Research into the causes of and solutions to the falling numbers of Antipodean wandering albatrosses includes an annual visit to the breeding grounds on Antipodes Island, and this report describes the results of the field programme in the 2020/2021 and 2021/2022 breeding seasons.

In total 93 pairs nested in the study area in 2021 and 90 pairs in 2022. The number nesting in 2022 across the whole island was estimated to be 2,927 pairs, the second lowest ever recorded. Measurement of female survivorship in 2020–2022 was detrimentally affected by the very late timing of fieldwork in March 2020, artificially exacerbating existing high interannual variation in female survivorship. While the population has been approximately stable for the last three years, there is no sign of recovery.

Most of the 40 courting and breeding albatrosses to which satellite transmitters were attached in March 2020 (Elliott & Walker 2020) survived the year, but one male breeder W-659 appeared to be killed on a Chinese long-line. Breeding birds and birds which had expected to breed but didn’t were found to retain their transmitters significantly longer in 2020 than non-breeders, presumably because feather moult is postponed whilst birds breed. While most of these transmitters were eventually lost at sea, one solar powered and two battery-powered transmitters were recovered from birds when they returned to Antipodes Island in January 2021.

In January 2021 a further 66 satellite transmitters were deployed, 36 on adults and 30 on chicks about to fledge. While most adults survived the year, the transmitters of three juveniles stopped close to pelagic long line vessels and may have been caught. In June 2021 another tagged juvenile, W-20k, was confirmed caught by a Taiwanese long-liner when its bands, along with the metal band of an adult female Antipodean wandering albatross O-805, not wearing a satellite tag, were recovered from the vessel. Given only a small proportion of the Antipodean wandering albatross population are banded (2.7%), to have caught two banded birds suggests many more birds without bands will also have been caught. Given the number of satellite transmitters deployed in 2019–2022 (220) and the number of days from which locations were received from the birds (38,812) the estimated reported fisheries related mortality of satellite-tagged birds is about 2% per annum. However, capture of satellite-tagged birds is likely considerably higher than 2% as the two captures that were documented came not from fishing operators voluntarily reporting bycatch, but from detection of an interaction from the combination of tracking data and Global Fishing Watch. It is likely that additional tagged birds whose transmitters stopped close to fishing vessels were also caught but their capture was not reported.

In January 2022, 50 satellite transmitters of two types were deployed on adult Antipodean wandering albatrosses. Soon after deployment data stopped being received from the 10 “Icarus” transmitters because of a failed data-agreement with Russia. The remaining 40 (30 on adults, 10 on juveniles) were of the second type of which 26 were still transmitting at the end of July 2022.”

Reference:

Walker, K. & Elliot, G. 2022. Antipodean wandering albatross satellite tracking and population study on Antipodes Island in 2021 and 2022. Nelson: Albatross Research  28 pp.

Posted 04 August 2022

Sealer’s Cave in 1948; the site where House Mice were first reported on Marion Island in August 1818 by William Phelps (“Webfoot”); photograph by Allan Crawford

The Mouse-Free Marion Project aims to eradicate the introduced House Mice of South Africa’s Marion Island that have taken to killing albatrosses and petrels.  The project has been initiated by BirdLife South Africa and the South African Department of Forestry, Fisheries and the Environment.  Upon successful completion, the project will have restored the critical breeding habitat of over two million seabirds (which includes eight ACAP listed species), many globally threatened, and improve the island's resilience to a warming climate.

The project will use helicopters to spread rodenticide bait pellets along pre-determined flight lines across Marion Island.  The entire land surface will be baited to ensure that sufficient bait is sown in every single mouse territory.  For success to be achieved each individual House Mouse needs to encounter and consume a lethal dose of bait, which is less than one pellet.

Entrance to a lava tunnel on the lower slopes of Fred’s Hill; photograph by Ian Meiklejohn

Caves and lava tunnels (or tubes) occur across Marion Island.  Mice certainly occur within these features, being recorded in caves as far back as 1818, the earliest year mice are known to be present on the island (click here).  Trials on Marion and Gough (using mark/recapture techniques) have found that cave-dwelling mice typically forage outside such features and consume bait whilst doing so.  However, this may not always be the case if mice are able to find sufficient food and moisture inside the larger caves or lava tunnels.  The mitigation strategy that will be adopted by the Project against the possibility that some mice may not forage outside is to identify such features and manually distribute bait inside them.

Inside Fred’s Cave looking towards the entrance.  Two mouse traps (marked with yellow reflective tape) are visible on the cave’s floor; photograph by Peter Ryan

Bait spread from helicopters will not penetrate deeply into these caves and lava tunnels, although some pellets will fall in or near their entrances.  To assist in the planning to treat these features by hand spreading bait, the project is compiling a register of known sites.  The above map lists the caves and lava tunnels that have already been identified by a number of individuals with knowledge and experience of Marion Island.  These will be ground-truthed by Elsa van Ginkel, the Mouse-Free Marion overwintering team member currently on the island.

The known caves and lava tunnels of Marion Island; the nine field huts are also shown

Hand baiting will also be undertaken around and underneath the buildings of the meteorological/research station, at the island’s nine field huts and at any other artificial structures in the field.  This will follow the accepted practice of hand baiting such structures while attempting eradication of rodents on seabird-breeding islands in the Southern Ocean.

With thanks to Keith Springer, Operations Manager, Mouse-Free Marion Project.

References:

Crawford, A.[B.] 1982.  Tristan da Cunha and the Roaring Forties.  Edinburgh & London: Charles Skilton.  256 pp.

Cuthbert, R.J., Visser, P., Louw, H., Rexer-Huber, K., Parker, G. & Ryan, P.G. 2011.  Preparations for the eradication of mice from Gough Island: results of bait acceptance trials above ground and around cave systems.  In: Veitch, C.R., Clout, M.N. & Towns, D.R. (Eds).  Island invasives: eradication and management.  Proceedings of the International Conference on Island Invasives.  Gland: IUCN.  pp. 47-50.

“Webfoot” [= William Dane Phelps] 1871.  Fore and Aft: or Leaves from the Life of an Old Sailor.  Boston: Nicholls & Hall.  359 pp.

John Cooper, ACAP Information Officer, 03 August 2022

From ship to shore: unloading rodenticide bait by helicopter; photograph from Tony Martin

Watch a recent video (webinar) that describes the successful eradication of rats and mice on South Georgia (Islas Georgias del Sur)* in the South Atlantic by its Project Leader.

“Find out what it was really like running the world's largest rodent eradication project in one of the most remote and challenging environments in this webinar that was recorded on 27 July 2022.  Project Leader, Professor Tony Martin, explains how he permanently had a knot of anxiety in his stomach for months at a time during the multi-year Habitat Restoration Project as he grappled with the uncertainties of the project. In this free online presentation, Tony tells us about the monumental heroics of ‘Team Rat’ to make the Habitat Restoration Project a historic success.

South Georgia [Islas Georgias del Sur*] has been free of rodents for a few years now, and Tony has had a chance to recover and reflect on the Habitat Restoration project.  He tells us about some of the lesser-known stories from behind the scenes.  The eradication was declared a success in 2018, and we also hear from Ecologist Alastair Wilson about some of the changes to the wildlife happening on the island since the rodents have gone.  And with his experiences of living in one of the few areas that were always rat-free, he describes how [the island] should be in the future once all the populations have fully recovered.”

Areas baited over three separate years, 2011-2015

John Cooper, ACAP Information Officer, 02 August 2022

*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.