Kieran Lawton

Status and distribution of wandering, black-browed and grey-headed albatrosses breeding at South Georgia

Long-term studies at Bird Island, South Georgia, show that numbers of wandering, black-browed and grey-headed albatrosses have been decreasing since the late 1970s. To determine the status of the total South Georgia population, all known colonies were censused in 2003/2004 using a combination of yacht-based digital photography and ground counts. The breeding population estimates from this census are 1,553 pairs of wandering albatross, 74,296 pairs of black-browed albatross and 47,674 pairs of grey-headed albatross. A 30% decline since 1984 was recorded for wandering albatross, and comparison of a sample of black-browed and grey-headed albatross colonies on the mainland of South Georgia photo-censused in both 1985/1986 and 2003/2004 indicates similarly substantial population declines. Unless these decreases can be halted or reversed, doubt will exist as to the long-term viability of these species of albatross at South Georgia.

An estimate of population sizes of burrowing seabirds at the Diego Ramirez archipelago, Chile, using distance sampling and burrow-scoping

The Diego Ramirez Islands lie 60 nautical miles southwest of Cape Horn and are the breeding site for three species of burrowing seabirds: blue petrels (Halobaena caerulea), common diving petrels (Pelecanoides urinatrix) and sooty shearwater (Puffinus griseus). Burrowing seabirds are highly vulnerable to predation by introduced vertebrate pests, and Diego Ramirez is an important breeding site because it is one of a few remaining subantarctic island groups with no introduced predators. Diego Ramirez is the only known breeding site for blue petrels in the southeast Pacific region, holding about 80% of the global population of that species, and with a population ten times larger than any other population in the world. We estimated the population size in 2002, using a novel application of the distance sampling technique to determine burrow density, and a burrow-scope with excavations to determine occupying species. We found that density was correlated with slope angle and soil wetness. Burrow densities in flatter terrain with drier soils were 2.03 burrows/m2 (95% confidence intervals: 1.82–2.27) and 1.11 burrows/m2 (0.84–1.48) in steeper terrain with wetter soils. The occupation rate of burrows were significantly different between habitat types (t=2.74, d.f. 11, P<0.05); in flatter drier habitats the proportion of burrows that led to a nest was 0.85 (0.74–0.96), in steeper wetter habitats this decreased to 0.64 (0.50–0.78). We used a digital elevation model to calculate true area rather than planar area for the two habitat types on the main island of Bartolome, and charts to calculate planar area for the remainder of the archipelago. There were 1.35 (1.15–1.54) million pairs of blue petrels and 99,000 (65,000–134,000) pairs of common diving petrels on the archipelago. These are similar figures to those from the only previous estimate, made in 1980. We found breeding sooty shearwaters for the first time, and estimated a population of several thousand pairs. We emphasise the facility of distance sampling as an unbiased technique with practical advantages over commonly used area search methods for monitoring populations of burrowing seabirds. These advantages include increased survey efficiency allowing a larger sample size for a given effort and a correspondingly tighter estimation of density.

Estimates of Southern Rockhopper and Macaroni Penguin Numbers at the Ildefonso and Diego Ramírez Archipelagos, Chile, Using Quadrat and Distance-sampling Techniques

Abstract Populations of Southern Rockhopper (Euduptes chrysocome chrysocome) and Macaroni (E. chrysolophus) Penguins at key breeding sites in the Southern Hemisphere have declined substantially in the past 50 years, but their statuses at important breeding sites in southern Chile are poorly known. In 2002, at two of the largest breeding sites in Chile, the Ildefonso and Diego Ramírez Archipelagos, we determined the number of breeding pairs. Based on nest density checks (quadrat and/or point-distance techniques) in a sample of habitats and calculations of the areas of occupied terrain, we estimated there were 86,400 (CL95%: 54,000 to 135,000) Rockhopper pairs and 5,660 (2,280 to 11,900) Macaroni pairs at Ildefonso, and 132,721 (88,860 to 185,665) Rockhopper pairs and about 15,600 Macaroni pairs at Diego Ramírez. Combined, the archipelagos hold about 28% of the world population of Southern Rockhopper Penguins.

The Evangelistas Islets, Chile: a new breeding site for black-browed albatrosses

A previously undescribed population of black-browed albatrosses (Thalassarche melanophrys) is reported at the Evangelistas Islets, Straits of Magellan, Chile. The population was censused from aerial photographs taken on 13 October 2002 that yielded an estimate of the number of breeding pairs. A combined total of 4,670 pairs of black-browed albatrosses were found nesting at Elcano and Lobos Islets, 2 of the 4 islets in the Evangelistas group. This new record raises to four the number of breeding islands of this albatross species in Chile.

An estimate of the population sizes of Black-browed (Thalassarche melanophrys) and Grey-headed (T. chrysostoma) Albatrosses breeding in the Diego Ramírez Archipelago, Chile

Abstract The Diego Ramírez Archipelago, Chile, is the southernmost albatross breeding ground in the world and holds globally important numbers of Black-browed (Thalassarche melanophrys) and Grey-headed (T. chrysostoma) Albatrosses. A census in the Diego Ramírez Archipelago has been attempted only once, in 1980–81, with methods that were unlikely to determine population sizes accurately. The number of breeding pairs of both species was estimated in the incubation period of 2002 using a combination of aerial photography, ground-based photography, yacht-based photography and ground counts. All islands in the archipelago were surveyed. There were an estimated 55000 pairs of Black-browed and 17000 pairs of Grey-headed Albatrosses breeding at the archipelago. Based on the results of this census, and those for the other four known breeding locations, the populations of both species of albatrosses in Chile are considerably larger than previously reported, comprising ~20% of the Black-browed Albatrosses and 23% of Grey-headed Albatrosses in the world, with the largest populations of both species occurring in the Diego Ramírez Archipelago.

Recent trends in numbers of wandering ( Diomedea exulans ), black-browed ( Thalassarche melanophris ) and grey-headed ( T. chrysostoma ) albatrosses breeding at South Georgia

South Georgia supports globally important populations of seabirds, including the wandering albatross Diomedea exulans, black-browed albatross Thalassarche melanophris and grey-headed albatross T. chrysostoma, currently classified by the world Conservation Union (IUCN) as vulnerable, near threatened and endangered, respectively. Surveys of these species at South Georgia were conducted during the incubation stage in November 2014 to January 2015, repeating previous surveys conducted in the 2003/2004 season. Numbers of wandering albatrosses breeding annually at South Georgia decreased by 18% (1.8% per year) from 1553 pairs in 2003/2004 to an estimated 1278 pairs in 2014/2015. Over the same period, black-browed and grey-headed albatrosses decreased by 19% (1.9% per year) and 43% (5% per year), respectively. These represent a continuation of negative trends at South Georgia since the 1970s and are in contrast to some populations elsewhere, which have shown signs of recent recovery. Given the importance of South Georgia for these species, the ongoing population declines, and in the case of grey-headed albatrosses, an acceleration of the decline is of major conservation concern. Incidental fisheries mortality (bycatch) is currently considered to be the main threat. Although seabird bycatch has been reduced to negligible levels in the fisheries operating around South Georgia, wider implementation of effective seabird bycatch mitigation measures is required to improve the conservation status of the South Georgia populations of wandering, black-browed and grey-headed albatrosses. In addition, more research is required to investigate the respective roles of bycatch and climate change in driving these population trends.