An Antipodean Albatross in flight; photograph by Jordan Shand

The Conservation Services Programme of New Zealand’s Department of Conservation have published a report by Graham Parker (Parker Conservation, Dunedin, New Zealand) and colleagues on the Endangered Antipodean Albatrosses of Antipodes Island. 

The report’s Summary as follows:

The Antipodean wandering albatross Diomedea antipodensis antipodensis has been in decline since a population crash in 2005-07. Declining numbers appear to have been largely driven by high female mortality, but low chick production—with fewer birds breeding and reduced breeding success—has compounded the problem. To tease out the causes of falling numbers of Antipodean wandering albatrosses and identify the effectiveness of potential solutions, research includes an annual visit to the breeding grounds on Antipodes Island. This report describes the results of the field programme in the 2022/23 breeding season, and the preliminary findings from tracking of juveniles since January 2022. 

There are some signs that the rate of decline might be slowing. The number of Antipodean wandering albatrosses breeding has been roughly stable for the past four seasons, and female survival shows some suggestion of improving since 2014 (4-year rolling averages), although it is still highly variable year to year. Breeding success in 2022 at 72% approached the average pre-crash nesting success of 74%, although the mean 2006–2022 rate remains comparatively low at 62%. However, the actual number of chicks produced remains small, even in good breeding-success years, since numbers nesting remain low. Recruitment is starting to draw from the (much smaller) cohorts produced since the crash, so population numbers will soon no longer be supplemented by higher recruitment rates seen over the past decade. 

The population has been approximately stable for the last four years. However, there is so far no evidence of any sustained improvement in Antipodean wandering albatross demography, as required for the population to recover, with tentative improvements recorded here merely slowing the decline. 

Recommendations include ongoing mark-recapture monitoring of demographic and population-size trends; an island-wide population size estimate; and research into causes of declines. More-targeted ongoing engagement is also needed, internationally and domestically, to achieve better bycatch mitigation in line with ACAP best practice. 

Reference:

Parker G.C., Rexer-Huber K., Walker K., Elliott G. 2023. Antipodean wandering albatross population study 2023. Final report to the Department of Conservation. Parker Conservation, Dunedin. 21 p. 

15 September 2023

A Vulnerable White-chinned Petrel at sea; photgraph by Petre Ryan

The Conservation Services Program of New Zealand’s Department of Conservation has released a report by Kalinka Rexer-Huber (Parker Conservation, Dunedin, New Zealand) and colleagues on the White-chinned Petrel Procellaria aequinoctialis population of the Antipodes Island. 

The report’s Summary follows:

This study provides an updated estimate of the white-chinned petrel (Procellaria aequinoctialis) breeding population size on Antipodes Island. We also detail the setup of a mark-recapture study suitable for estimating key vital rates and detecting population change, adult survival in particular. Lastly, we document blood and feather collection for a wider study on mercury contamination, and deployment and recovery of time-depth recorders for data on dive depth of white-chinned petrels. 

Population size estimate. Burrow density is estimated from a representative sample of burrowed areas then corrected for burrow occupancy and extrapolated to the available area of nesting habitat to estimate the breeding population of white-chinned petrels. For an estimate as accurate and precise as possible we built on previous efforts in 2009–11 and 2021–22 (Thompson 2019; Elliott & Walker 2022). To estimate burrow density we used the distance sampling dataset from 2021–22 and expanded the sampling coverage across the whole island, adding 93 transects to a new total of 248 island-wide sampling locations. Distance sampling enabled burrow density estimates that explicitly account for burrow detectability. Occupancy was assessed by inspecting 293 burrows just after laying, calculating rates and corrections using the approach developed for the 2009–11 study (burrow numbers corrected for entrances that are not in fact burrows, and for other species using white-chinned petrel burrows). The area used by white-chinned petrels, with two habitat types distinguishable, was drawn from comprehensive habitat mapping 2021–22. Antipodes Island had an estimated 26,400 (95% CI: 22,200–31,600) white-chinned petrel pairs breeding in Dec 2022 during early incubation. Burrow detectability was different in the two habitat types and occupancy rates differed, so for accuracy the estimate used burrow density, area and occupancy specific to each habitat type. These refinements to 2009–11 and 2021–22 methods result in a population size estimate here that is smaller but more accurate and precise. 

Demographic study setup. Population change is more readily detected via intensive study of birds in a representative study population, so we established a mark-recapture study to estimate vital rates, survival in particular. Marked burrows in two study areas contain 169 banded white-chinned petrels. For accurate, precise survival estimates this marked population needs building further, along with recaptures at existing marked burrows for a minimum of three years. 

Recommendations. An efficient and effective long-term monitoring strategy could combine annual intensive monitoring effort in a representative study population, as set up here, supplemented by occasional whole- island population size estimates (5–10-year intervals). Ongoing mark-recapture will enable robust trend estimation over time, with whole-island estimates providing occasional more-general overview of breeding numbers. 

Reference:

Rexer-Huber K., Parker G.C., Elliott G., Walker K. 2023. Antipodes white-chinned petrel population size and survival study setup. Final report to the Department of Conservation. Parker Conservation, Dunedin. 18 p. 

13 September 2023

Not a cool situation. An albatross chick is near buried among flowering Verbesina on Midway, photograph from the US Fish and Wildlife Service

Following the failure of the House Mouse Mus musculus eradication effort on Midway Atoll in the North Pacific this year as recently reported, more positive news is to hand on another eradication effort, to rid both Sand and Eastern Islands within the atoll of the introduced Golden Crownbeard Verbesina encelioides. This invasive plant forms “chest-high, impenetrable thickets” in which breeding Black-footed Phoebastria nigripes and Laysan P. immutabilis Albatrosses have difficulty reaching and departing from their nest sites, become entangled, and their well-insulated, downy chicks overheat due the plants' sheltering effect against cooling sea breezes.

Before (2011) and after (2023) views on Eastern Island from the same spot. The dense Verbesina has been replaced with “outplanted” native grass Eragrostis variabilis, photographs by Pete Leary (top) and Jon Brack (bottom)

In May 2000 I spent a week on Midway following the Second International Conference on the Biology and Conservation of Albatrosses and other Petrels, held in Honolulu, Hawaii. Along with other conference delegates (we filled a whole plane to get there). I experienced the dense Verbesina stands with albatrosses breeding among them on both Sand and Eastern Islands. As the before and after photographs taken over a decade apart show, a concerted effort since my visit to remove plants and exhaust the seed load within the sandy soil shows remarkable differences. Study plots on both islands have demonstrated the value of clearing away the daisy-like plant with breeding success almost doubling in treated areas, compared to untreated controls. With atoll-wide eradicatioin hopefully approaching the last remaining one percent of Verbesina is being targeted by cutting paths through the native vegetation to access the remaining mature plants to remove their flower heads before they set seed and to find seedlings which are then sprayed with herbicide (click here).

This Laysan Albatross on its nest is covered with a tangle of collapsed Verbesina stems, photograph by Matt Brown

Read an earlier article on the eradication effort in ACAP Latest News here.

John Cooper, Emeritus Information Officer, Agreement on the Conservation of Albatrosses and Petrels, 12 September 2023

 A fledgling Black Petrel; photograph by Elizabeth (Biz) Bell, WMIL

A report by Elizabeth Bell (Wildlife Management International Ltd, New Zealand) and colleagues on the tākoketai/Black Petrel, Procellaria parkinsoni of Aotea/Great Barrier Island has been released by New Zealand’s Department of Conservation (NZDOC). Research for the report, Key demographic parameters and population trends of black petrels (Procellaria parkinsoni) – 2022/23, was carried out over the 2022/2023 breeding season.

The summary from the NZDOC website follows: 

"During the 2022/23 breeding season 480 tākoketai/black petrel study burrows were intensively monitored within the Mt Hobson/Hirakimata study area on Aotea/Great Barrier Island. 

There were 313 (65.2%) burrows occupied by breeding pairs, 64 (13.3%) occupied by non-breeding birds, and 103 (21.5%) were unoccupied. Overall, 191 chicks were produced from the study burrows representing a fledgling success rate of 61%, but 13 chicks were found to be below weight and smaller in size during the May chick banding trip, and most of these chicks were not expected to survive to fledging. This would further reduce breeding success to 56.9%. 

Breeding success was impacted by weather events, specifically the Auckland flood event on 27 January 2023 and Cyclone Gabrielle between 12-16 February 2023. A number of burrows flooded, causing eggs to fail and small chicks to drown or chill and die, and foraging success of parents appeared to be reduced with 13 chicks being in poor condition by May prior to fledging. 

Nine census grids were monitored within the study area and accounted for 197 of the inspected study burrows. Of these, 119 were occupied by breeding pairs (60.4%) and 68 chicks were produced representing a fledging success rate of 57.1%. Again 7 of these chicks were in poor condition and were not expected to fledge, reducing breeding success to 52.1%. 

A total of 664 adults and 129 fledgling chicks were captured during the 2022/23 field season with 174 adults banded this season (including 52 from study burrows). Of the 129 fledgling chicks banded during the 2022/23 field season, 119 were banded in study burrows; 72 could not be banded due to torrential rain over the chick banding trip, and one had already fledged prior to the banding visit in May 2023. 

There have been a total of 420 returned chicks recaptured at the colony since they were banded prior to fledging. Of these, 117 returned chicks were identified during the 2022/23 breeding season; 28 of which were caught for the first time at the colony. The majority of all 420 returned chicks were from the 2016/17 breeding season, followed by the 2013/14 cohort. Not all cohorts were represented as no returned chicks from the 1995/96, 1996/97 and 1997/98 cohorts were recaptured this season. Understanding the factors affecting return rates of chicks within the 35-ha study site is vital. It is important to determine whether it is related to low juvenile survival and/or recruitment or if it is simply due to a lack of detection. Understanding juvenile survival and recruitment is necessary for accurate demographic modelling and for species risk assessment modelling. Therefore, it is recommended that effort to obtain this data is completed with urgency. 

Additional monitoring of pig and other predator occurrence and impact on black petrels on Cooper’s Castle was undertaken this season. Eighteen black petrel burrows were identified within the boundaries of this study area; three were breeding sites and four sites were being visited by non- breeding birds. All other burrows were empty. Trail cameras were placed along pig pathways, walking tracks and outside active black petrel burrows. Footage confirmed feral pig, rat, and feral cat presence. While no interactions with black petrels were caught on camera at Cooper’s Castle, there was one cat predation of an unbanded adult and one chick from a random, non-monitored burrow. There was one rat predation event at the study colony on Hirakimata this season. Introduced species still pose a threat to the black petrel population and it is imperative pest control measures continue."

Reference:

Bell, E.A., Lamb, S. & Maclean, C. 2023. Key demographic parameters and population trends of tākoketai/black petrels (Procellaria parkinsoni) on Aotea/Great Barrier Island: 2022/23. POP2022-01 final report prepared by Wildlife Management International Ltd for the Conservation Services Programme, Department of Conservation, Wellington. 41 p.

07 September 2023