Salvin’s Albatrosses on Proclamation Island, Bounty Islands, from a drone photograph in the report

Graham Parker & Kalinka Rexer-Huber (Parker Conservation, Dunedin, New Zealand) have produced a final report for the Conservation Service Programme (CSP) of the New Zealand Department of Conservation on the use of drone photographs to count breeding albatrosses at the sub-Antarctic Bounty Islands.

A CSP summary separate to the report follows:

“Salvin’s albatross Thalassarche salvini are a Nationally Critical seabird endemic to New Zealand. They breed at two sites, predominantly at the Bounty Islands, and are one of the New Zealand seabird species most at risk from fisheries bycatch. The population status at the Bounty Islands is poorly known due to logistical difficulties in conducting research at this remote location, and differences and inherent uncertainties in methods previously used to assess population status. By extrapolating densities from one island, population sizes of 76,000 and 31,000 pairs across the group were estimated in 1978 and 1997, respectively. Method differences, including in how densities and areas were estimated, led to targeted repeat censuses of marked areas that over time gave worrying data on trends (30% decline in breeding pairs between 1997 and 2011). Repeat counts for trend assessment, however, need to be complemented by whole-population size estimates because a small count site may or may not remain representative of changes in the whole population over time.

Because many of the islands are inaccessible to boat-based landings, aerial photographs appear to be the best way to estimate population numbers across the whole Bounty Island group and assess trends over time. Aerial photographs taken from fixed-wing aircraft have been used to count Salvin’s albatross in the past. Estimates ranged between 42,800 and 60,400 birds, although not all birds counted in photographs will have been breeding. However, surveys involving aeroplane charter or helicopters are logistically demanding and expensive, so other methods for aerial surveys are being explored. Population monitoring by drones hold promise as an alternative way to obtain aerial photographs suitable for estimating albatross numbers at reduced effort and cost. Also known as unmanned aerial vehicles (UAV), drones are increasingly used for seabird population assessment and monitoring worldwide. In the New Zealand subantarctic, drones have been used successfully for a range of wildlife monitoring at the Antipodes and Auckland Islands. Relative to piloted aerial surveys, drone surveys have low operational costs, simple logistical requirements, and are relatively low risk for operators, while providing data that are systematic, repeatable, and accurate. Some constraints are similar, particularly the impact of wind, rain, and haze on image acquisition. As with any survey method drones also have limitations, notably in battery life and potential for wildlife disturbance.

Effects on animals are becoming better documented as drone use for wildlife surveys becomes more common. To date, drones have been used at the Bounty Islands primarily to assess the potential for wildlife disturbance. The islands are densely populated with fur seals Arctocephalus forsteri, erect-crested penguins Eudyptes sclateri and smaller seabirds as well as the Salvin’s albatrosses, so the potential for disturbance by drones was assessed carefully. Disturbance of animals on the ground or in the air was minimal provided the drone was flown with due caution (avoiding seal clusters near launch site, flight height assessed relative to flying bird density but not below 20m flight height).

We discuss the implications of data quality in this report for future potential drone-based estimates of the population size of Salvin’s albatross at the Bounty Islands, and provide recommendations for how best to deal with some of the uncertainties inherent in aerial count data. To assess if drone-image counts are comparable with existing data (photo counts from aircraft, ground counts), we then do whole-island counts of Salvin’s albatross on all islands that have had drone overflight (Proclamation, Spider, Tunnel and Ranfurly Islands). We document baseline drone counts, compare results to those from other methods, and discuss the relative utility of survey methods.”

Reference:

Parker, G.C. & Rexer-Huber, K. 2020.  Drone-based Salvin’s albatross population assessment: feasibility at the Bounty Islands. Final report to Department of Conservation, Marine Species and Threats July 2020.  Dunedin: Parker Conservation.  18 pp.

John Cooper, ACAP Information Officer, 19 October 2020

Southern Royal Albatrosses display on Campbell Island

 The Conservation Service Programme of New Zealand’s Department of Conservation has published four final reports for project BCBC2019-03: Seabird population research, Campbell Island 2019/20 that cover population monitoring and surveys conducted on albatrosses and petrels on the island during the austral summer.

The following text summarizing the four reports comes from the Department of Conservation:

Field survey component

The objectives of this project were to collect photo-point and ground-truthing data at Campbell and grey-headed albatross colonies, repeat whole-island counts of breeding Northern giant petrels, collect GLS trackers from Southern royal albatrosses, use sound recorders to record burrowing petrel distribution and check the bands of all banded birds seen. The 1996 census of breeding Northern giant petrels (Macronectes hallii) around the island was repeated. Adjusting chick counts to correct for breeding failures gave an estimated 150 (range 134–173) breeding pairs in 2019. This appears broadly similar to the last count in 1996. Three tracking devices were recovered from Southern royal albatrosses (Diomedea epomophora). Numbers of Southern royals in the Col-Lyall colony seemed low, highlighting the need to repeat the island-wide census last done 2004–08, and to resume mark-recapture in the study colony to assess the population’s current status. Sound recorders captured white-headed petrels (Pterodroma lessonii) calls at Campbell Island, supporting the idea that a small population may breed there. Recorders also provided evidence that white-chinned petrels (Procellaria aequinoctialis) are recolonising multiple areas on the main Campbell Island from its offshore islets, extending the known distribution northward to Northwest Bay and Switchback Ridge.

Photo count component

Aerial photographs were taken during two Navy helicopter flights along the coast, six days apart in mid-to-late November 2019. Ground-level photographs were taken from 14 fixed vantage points overlooking the eight sites where mollymawks breed. Information on overall numbers were derived for the larger colonies from the aerial photographs, supplemented by more detailed information on species composition and what proportion of the birds were sitting on nests or standing (occasionally sitting) around, either as partners of nesting birds, or as courting pre-breeders, or simply just loafing.

Overall, an estimated 22,766 Campbell Mollymawks and 5,937 Grey-headed Mollymawks appeared to be occupying nests, although not all of these necessarily involved a bird sitting on an egg. In a contemporaneous survey at the Bull Rock South colony, 18% of occupied nests were empty. If this figure applies more widely, the actual number of breeding pairs at the time of the survey could be lower: 18,668 and 4,868 pairs of Campbell and Grey-headed mollymawks, respectively. A further 4,933 Campbell Mollymawk individuals (just under 18 % of the species’ total) and 1,344 Grey-headed Mollymawks (just over 18 % of that species’ total) were recorded loafing. The November 2019 survey was carried out about three-fifths of the way through the species’ incubation period, assuming peak egg laying around 10th October. By the time of the survey, some nests would have failed, so the initial number of nests will be higher. Using regression formulae developed during earlier surveys to account for these losses, the number of nesting Campbell and Grey-headed Mollymawk pairs at the start of the 2019 breeding season was estimated to be 24,338 and 6,429, respectively.

These figures, compared with those covering the past 25 years, suggest that the Campbell Mollymawk population is relatively stable, whereas the Grey-headed Mollymawk population has continued to decline by around 0.84 % per annum since the mid-1990s.

Southern Royal Albatross breeding assessment

A March 2020 trip to Campbell Island included follow-up work from the November 2019 trip in addition to work focusing on southern royal albatross (Diomedea epomophora). The main aims were retrieving GLS devices, resighting bands and PIT tags, and conducting nest counts of southern royal albatross in the Col study area (and Honey index area, if time permitted). Nest counts would be used to gain insight into population trends and provide a ground count to compare to aerial photographs and satellite imagery. Aerial photographs of the Campbell (Thalassarche impavida) and grey-headed albatross (T. chrysostoma) colonies at Bull Rock and adjacent north-eastern colonies were repeated from November to determine breeding success. Sound recorders were deployed on Beeman Hill to assess abundance and distribution of petrels.

Mollymawk chick numbers and survival

An aerial photographic survey of the mixed Campbell Mollymawk, T. impavida, and Grey-headed Mollymawk, T. chrysostoma, colonies along the north-east coast of Campbell Island was carried out on 17 March 2020. At this time, most of the birds present at these colonies would have been chicks. The aim of the study was therefore to establish the number of chicks in these colonies and relate this to the number of nesting adults estimated from a combined aerial and ground level photographic survey carried out earlier in the nesting season in November 2019. Campbell Mollymawks made up 90 % of these nesting birds, with Grey-headed Mollymawks the remainder. Overall nesting success at the mixed mollymawk colonies along the north-east coast of Campbell Island during the 2019–20 breeding season was 50–60 %, with a best estimate of around 58 %. This is broadly in line with the level of nesting success measured for Campbell Mollymawk during 1984–96, the predominant species present in these colonies.

A Grey-headed and a Campbell Albatross interact on Campbell Island, photographs by Rachael Orben

References:

Frost, P.G.H. 2020.  Status of Campbell Island and Grey-headed Mollymawks on the northern coasts of Campbell Island, 2019.  Whanganui: Science Support Service.  25 pp.

Frost, P. & Mischler, C. 2020.  Mollymawk Chick Numbers and Survival on Campbell Island, November 2019-March 2020.  Whanganui: Science Support Service & Twizel: Department of Conservation.  14 pp.

Mischler, C. 2020.  Campbell Island/ Motu Ihupuku Seabird Research March 2020.  Twizel: Department of Conservation.  25 pp.

Rexer-Huber K., Parker K.A. & Parker G.C. 2020.  Campbell Island Seabirds: Operation Endurance November 2019.  Final Report to Department of Conservation, Marine Species.  April 2020.  Dunedin: Parker Conservation.  23 pp.

Reports available here.

John Cooper, ACAP Information Officer, 16 October 2020

Individual or population effect?  A decomposing Laysan Albatross chick with a heavy plastic load on Midway Atoll

 Jesse Senko (School for the Future of Innovation in Society, Arizona State University, Tempe, USA) and colleagues have published open access in the journal Endangered Species Research reviewing evidence for population effects from plastic pollution in seabirds and other marine vertebrates: “no study in the past 50 yr reported direct evidence of population-level effects”.

The paper’s abstract follows:

“Plastic pollution is increasing rapidly throughout the world’s oceans and is considered a major threat to marine wildlife and ecosystems. Although known to cause lethal or sub-lethal effects to vulnerable marine megafauna, population-level impacts of plastic pollution have not been thoroughly investigated. Here, we compiled and evaluated information from peer-reviewed studies that reported deleterious individual-level effects of plastic pollution on air-breathing marine megafauna (i.e. seabirds, marine mammals, and sea turtles) worldwide, highlighting those that assessed potential population-level effects. Lethal and sub-lethal individual-level effects included drowning, starvation, gastrointestinal tract damage, malnutrition, physical injury, reduced mobility, and physiological stress, resulting in reduced energy acquisition and assimilation, compromised health, reproductive impairment, and mortality. We found 47 studies published between 1969 and 2020 that considered population-level effects of plastic entanglement (n = 26), ingestion (n = 19), or both (n = 2). Of these, 7 inferred population-level effects (n = 6, entanglement; n = 1, ingestion), whereas 19 lacked evidence for effects (n = 12, entanglement; n = 6, ingestion; n = 1, both). However, no study in the past 50 yr reported direct evidence of population-level effects. Despite increased interest in and awareness of the presence of plastic pollution throughout the world’s oceans, the extent and magnitude of demographic impacts on marine megafauna remains largely unassessed and therefore unknown, in contrast to well-documented effects on individuals. Addressing this major assessment gap will allow researchers and managers to compare relative effects of multiple threats—including plastic pollution—on marine megafauna populations, thus providing appropriate context for strategic conservation priority-setting.”

Reference:

Senko, J.F., Nelms, S.E., Reavis, J.L., Witherington, B., Godley, B.J. & Wallace, B.P. 2020.  Understanding individual and population-level effects of plastic pollution on marine megafauna.  Endangered Species Research 43: 234-252.

John Cooper, ACAP Information Officer, 15 October 2020

 A colour-banded Antipodean Albatross on Antipodes Island, photograph by Kath Walker

Graeme Elliott & Kath Walker (Department of Conservation, New Zealand) have reported to the Department's  Conservation Service Programme on their most recent field trip to study globally Endangered and Nationally Critical Antipodean Albatrosses Diomedea antipodensis on Antipodes Island.

The report’s abstract follows:

“The Antipodean wandering albatross Diomedea antipodensis antipodensis has been in decline since 2007. 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.

Difficulty reaching Antipodes Island in the 2019/20 summer meant field studies were undertaken much later than usual, and the COVID-19 pandemic meant less than two weeks was spent on Antipodes Island, from 15–28 March 2020. As a result, assessment of 2019 nesting success (59%) was a little coarser than previously and the chicks had all fledged before we arrived to band them. It also meant that birds which visited Antipodes Island to breed but failed early, or which left the island early after failing to find their usual breeding partner, were not recorded. This included birds wearing satellite transmitters in 2019 whose survival after their transmitters stopped working could not be verified.

Only 75 pairs nested in the study area in 2020, amongst the lowest recorded, but female survival in 2019 had increased over previous years, at least amongst non-breeding females. Breeding female survivorship in 2019 was at an unsustainable 74%, though this estimate was likely affected by the late timing of Antipodes Island fieldwork in 2020. There is so far, no evidence of the sustained improvement in female survival necessary for the population to recover.

Since 2009 there has been an estimated 1,000 “extra” deaths per year of adult albatrosses over and above their normal mortality, and if the mortality rate amongst younger pre-breeding birds is similar, then approximately 1,300 “extra” deaths per annum also occurred amongst younger birds. This suggests that since 2004 about 15,000 “extra” adults have died, and about 20,000 “extra” pre-breeding birds, of which about 70% have been female.

Forty satellite transmitters were deployed in mid-March 2020, 25 on females (10 breeding) and 15 on males (7 breeding). Half were battery-powered and the remaining 20 transmitters were solar-powered. Most of the birds were adults which had bred before, but nine were relatively young female pre-breeders (7–11 years old). This deployment aims to identify fishing fleets with high levels of spatial and temporal overlap with Antipodean wandering albatrosses in 2020.”

 Kath Walker and Graeme Elliott on Antipodes Island, with a curious Antipodean Albatross

Reference:

Elliott, G. & Walker, K. 2020.  Antipodean wandering albatross: satellite tracking and population study Antipodes Island 2020.  Wellington: Conservation Services Programme, Department of Conservation.  54 pp.

John Cooper, ACAP Information Officer, 14 October 2020