Jose Valencia

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.

Genetic affinities of newly sampled populations of Wandering and Black-browed Albatross

Abstract This study extends previous phylogeographic genetic studies of the Black-browed and Wandering Albatross species complexes through the addition of newly acquired genetic data from wandering-type albatrosses on Macquarie Island and Black-browed Albatrosses (Thalassarche melanophrys) on Macquarie Island and the Chilean islands of Diego de Almagro and Ildefonso. DNA sequencing of Domain I of the mitochondrial control region showed that the wandering-type albatrosses on Macquarie Island belong to the Diomedea exulans group and show close genetic affinity to populations on the Prince Edward and Crozet Islands. The populations of Black-browed Albatrosses on Diego de Almagro, Ildefonso and Macquarie Islands all fell into a distinct grouping that also included birds from Diego Ramirez, South Georgia and Kerguelen Islands. Both the Wandering and Black-browed species complexes show multiple distinct lineages, some with disjunct geographical distributions. We suggest that this is a consequence of prolonged isolation of populations during the Late Pleistocene followed by range expansion of D. exulans and T. melanophrys after glacial retreat from many subantarctic islands. Both species most likely dispersed from populations centred in the southern Indian Ocean.

Gastrointestinal parasite fauna of gentoo penguins ( Pygoscelis papua ) from the Península Munita, Bahía Paraíso, Antarctica

An increase in interest in the diseases of seabirds has developed as a part of a worldwide strategy for environmental conservation (Clarke & Kerry 1993, Jones & Shellam 1999). According to Clarke & Kerry (1993) most studies on penguin enteroparasites were published before 1986 and most of them are post mortem diagnoses. This paper provides new data on the intestinal parasitic fauna of gentoo penguins nesting on the Antarctic Península.

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.