Anthony Caravaggi (School of Biological, Earth and Environmental Sciences, University College Cork, Ireland) and colleagues have yesterday published open access in Ibis - International Journal of Avian Science on estimates of the numbers of breeding seabirds killed annually on UK's Gough Island by the now notorious “killer” House Mice Mus musculus.  Among the 1.5-2.1 million seabirds of 10 species estimated to be killed annually is the ACAP-listed and Critically Endangered Tristan Albatross Diomedea dabbenena, which fledges 650-750 less chicks a year due to mice attacks.  As a consequence this near-endemic albatross is thought to be heading for extinction if the mice are not eradicated, planned to be attempted in 2020.

A male Tristan Albatross stands over its downy chick on Gough Island, photograph by Andrea Angel & Ross Wanless

The paper’s abstract follows:

“Invasive species are the main threat to island biodiversity; seabirds are particularly vulnerable and are one of the most threatened groups of birds. Gough Island, a UNESCO World Heritage Site in the South Atlantic Ocean, is an Important Bird and Biodiversity Area, and one of the most important seabird colonies globally. Invasive House Mice Mus musculus depredate eggs and chicks of most seabird species on the island, but the extent of their impact has not been quantified. We used field data and bootstrapped normal distributions to estimate breeding success and the number of surviving chicks for 10 seabird species on Gough Island, and compared estimates with those of analogous species from predator‐free islands. We examined the effects of season and nest‐site location on the breeding success of populations on Gough Island, predicting that the breeding success of Gough birds would be lower than that of analogues, particularly among small burrow‐nesting species. We also predicted that winter‐breeding species would exhibit lower breeding success than summer‐breeding species, because mice have fewer alternative food sources in winter; and below‐ground nesters would have lower breeding success than surface nesters, as below‐ground species are smaller so their chicks are easier prey for mice. We did indeed find that seabirds on Gough Island had low breeding success compared with analogues, losing an estimated 1 739 000 (1 467 000–2 116 000) eggs/chicks annually. Seven of the 10 focal species on Gough Island had particularly high chick mortality and may have been subject to intense mouse predation. Below‐ground and winter breeders had lower breeding success than surface‐ and summer‐breeders. MacGillivray's Prion Pachyptila macgillivrayi, Atlantic Petrel Pterodroma incerta and Tristan Albatross Diomedea dabbenena are endemic or near‐endemic to Gough Island and are likely to be driven to extinction if invasive mice are not removed.”

Read a popular article on the paper's findings by Alex Bond, one of its authors, here.  Also see an RSBP blog by Laura Beasley that gives information on the Gough Island Restoration Programme.  More reports on the publication here and here.

With thanks to Laura Beasley and Anthony Caravaggi.

Caravaggi, A., Cuthbert, R.J., Ryan, P.G., Cooper, J. & Bond, A.L. 2018.  The impacts of introduced House Mice on the breeding success of nesting seabirds on Gough Island.  Ibis doi.org/10.1111/ibi.12664.

John Cooper, ACAP Information Officer, 23 October, 2018

Henri Weimerskirch (Centre d’Etudes Biologiques Chizé, Villiers-en-Bois, France) and colleagues have published on numbers of French sub-Antarctic albatrosses in the journal Polar Biology.

The paper’s abstract follows:

“Today albatrosses are threatened worldwide, especially by fishing activities, and many populations are currently in decline. Albatrosses breeding at the French Southern Territories in the south-western Indian Ocean, on the Crozet, Kerguelen and Saint-Paul–Amsterdam island archipelagos, are monitored regularly. This monitoring has been based on a sample of species and sites, and there was a need for an assessment of the population trends for all species at each site. During the past 3 years most populations have been surveyed, allowing an assessment of the trends of albatrosses breeding at the archipelagos of the French Southern Territories over the past 40 years. Wandering Albatrosses show similar trends at all sites within the Crozet and Kerguelen archipelagos, with a recent recovery of colonies after strong declines in the 1970s. Amsterdam Albatrosses are increasing, albeit at lower rates during recent years. Indian Yellow-nosed Albatrosses show a global decline over the entire range. The trends among Black-browed and Grey-headed Albatrosses vary between colonies and archipelagos. Sooty Albatrosses have continuously decreased in numbers whereas Light-mantled Albatross numbers vary considerably between years, with an overall increase over the past 30 years. These results confirm that the French Southern Territories in the south-west Indian Ocean support a significant portion of the world populations of several albatross species. Several species appear to be steadily decreasing probably because of the impact of fisheries and disease outbreaks. The reasons for different trends among populations of the same species are not well understood and require further investigation.”

Saint-Paul Island, photograph by Thierry Micol

Indian Yellow-nosed Albatross and chick, photograph by Jeremy Demay

Reference:

Weimerskirch, H., Delord, K., Barbraud, C., Le Bouard, F., Ryan, P.G., Fretwell, P. & Marteau, C. 2018.  Status and trends of albatrosses in the French Southern Territories, Western Indian Ocean.  Polar Biology 41: 1963-972.

John Cooper, ACAP Information Officer, 22 October 2018

Georgios Karris (Department of Environmental Technology, Technological Educational Institute of Ionian Islands, Panagoula, Zakynthos, Greece) and colleagues have published on fishery discards taken by Scopoli’s Shearwaters Calonectris diomedea (Least Concern) in the eastern Mediterranean in the light of proposed Common Fishery Policy reforms in the open-access journal Avian Research.

The paper’s long abstract follows:

“Background

The banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban on discards on top marine predators such as seabirds is largely unknown, especially in oligotrophic systems of the Mediterranean. The current study investigates the presence of scavenging seabirds around fishing trawlers as well as the exploitation of discards produced by bottom trawlers in the eastern Ionian Sea.

Methods

On-board observations were randomly conducted in May and December 2014, in order to record the presence and use of fishery discards by two common seabird species, namely, Scopoli’s Shearwater (Calonectris diomedea) and the Yellow-legged Gull (Larus michahellis).

Results

A total of 3400 seabirds were counted during May of which 2190 individuals were Scopoli’s Shearwaters and 1210 were Yellow-legged Gulls. The latter species was the only scavenger observed during winter and in total, 768 individuals were counted. Differences in species abundance in the study area are related to breeding phenology and migratory movements. The number of seabirds attending bottom trawler operations during morning and afternoon hours showed no significant differences for both seabird species. Both scavenging seabirds extensively exploited fishery discards, which were mainly demersal fish, and consumed 70–80% of the total fishery discards biomass; however, they appeared to avoid poisonous species and/or large-sized fish. Yellow-legged Gulls displayed kleptoparasitic behaviour on Scopoli’s Shearwater during feeding experiments. The number of such incidents depended on the number of gulls around the fishing vessel, with more than 90% success rates.

Conclusions

Considering the average annual biomass of discards estimations and the consumption rate found in this work, 106.1–117.9 t may be offered as a food subsidy to scavenging seabirds in the study area and should support a substantial part of local populations. Our results constitute baseline information on the annual amount of fishery discards and their exploitation rate by seabirds in the Ionian Sea, and suggest further work for a complete understanding of the potential impacts of the discards reform bill on seabirds.”

Scopoli's Shearwater, photograph by Benjamin Metzger

Reference:

Karris, G., Ketsilis-Rinis, V.,Kalogeropoulou, A., Xirouchakis, S., Machias, A., Maina, I. & Kavadas, S. 2018.  The use of demersal trawling discards as a food source for two scavenging seabird species: a case study of an eastern Mediterranean oligotrophic marine ecosystem.  Avian Research https://doi.org/10.1186/s40657-018-0118-5.

John Cooper, ACAP Information Officer, 19 October 2018

Georgios Karris (Department of Environmental Technology, Technological Educational Institute of Ionian Islands, Panagoula, Zakynthos, Greece) and colleagues have published open access in the journal Wildlife Biology on aspects of the foraging ecology of Scopoli's Shearwater Calonectris diomedea (Least Concern) breeding within Greece.

The paper’s abstract follows:

“Pelagic seabirds that breed colonially are central-place foragers; their spatial distribution is restricted to marine areas around their colonies during the chick-rearing period, when attendance and food provision to their chicks has to be intense. In this study we analyzed the foraging trips of 11 Scopoli's shearwater Calonectris diomedea breeders that were tagged with GPS data loggers during 2014 in oligotrophic waters (Ionian Sea, western Greece), and assessed the range and oceanographic parameters of their foraging habitat. Contrary to previous findings suggesting a varying foraging strategy depending on the breeding stage, the tracked shearwaters made short trips, less than 4 days long, in the vicinity of the colony. By applying the Adaptive Kernel method, their 50% and 95% foraging range was estimated at 6871 km² and 23 014 km² respectively. In addition, generalized additive models showed that sea surface temperature (<25.5°C), minimum distance from the colony (<100 km), fishing pressure index from small scale fisheries (medium values) along with a two-dimensional soap film smoother for space (easting, northing) were the most significant factors affecting at-sea distribution of this marine top predator during the early chick-rearing period (i.e. 99.9% of the final model deviance). Our study will contribute to the revision of the boundaries of the local Special Protection Area (SPA) of Strofades. It will also address the implementation of specific conservation measures for the species at regional and national scale, and the development of a management plan for the protection of the study area.”

Scopoli's Shearwater at sea, photograph by 'Pep' Arcos

With thanks to Georgios Karris.

Reference:

Karris, G., Xirouchakis, S., Maina, I., Grivas, K. & Kavadas, S. 2018.  Home range and foraging habitat preference of Scopoli's shearwater Calonectris diomedea during the early chick-rearing phase in the eastern Mediterranean.  Wildlife Biology doi.org/10.2981/wlb.00388.

John Cooper, ACAP Information Officer, 18 October 2018