Roberto Schlatter

Seabird eggs as bioindicators of chemical contamination in Chile.

Seabird eggs were used as bioindicators of chemical contamination in Chile. Brown-hooded Gull (Larus maculipennis), Kelp Gull (Larus dominicanus), Trudeaus Tern (Sterna trudeaui), Neotropic Cormorant (Phalacrocorax brasilianus), and Pink-footed Shearwater (Puffinus creatopus) eggs were sampled at different breeding sites during the 1990s. Mercury and organochlorines (PCBs, DDT, HCB, HCH, and PCP) were quantified to reveal the interspecific differences, spatial and temporal trends in contamination levels. Trudeaus Tern displayed the highest levels of mercury (486 ng g(-1) wet weight). The highest sumDDT concentrations were measured in Brown-hooded Gulls (726 ng g(-1)). PCB levels were similar among the species (102-236 ng g(-1)), but the composition of the PCB mixture was different in Pink-footed Shearwaters. With the exception of the Brown-hooded Gull, all species studied presented similar and low levels of organochlorines (sumOHa). Residues of PCB and related compounds were not detected in any of the seabird eggs analyzed in Chile. Geographical variation was low, although levels of industrial chemicals were slightly higher in eggs from Concepción Bay, and agricultural chemicals in eggs from Valdivia. Also interannual variation was low, but some evidence was found of decreasing levels in gull eggs throughout the time of the study. The causes of the low levels and small variability in space and time of environmental chemicals in Chilean seabirds are discussed. We propose the use of seabirds in future monitoring of the development of chemical contamination in Chile.

Waterbird Assemblages and Habitat Characteristics in Wetlands: Influence of Temporal Variability on Species-Habitat Relationships

Abstract. Patterns of spatial and temporal variation in species richness, abundance and diversity were evaluated in eight wetlands in Central-South Chile in relation to nine wetland characteristics. Twenty-six bird species were recorded, among the most representative families were Rallidae, Ardeidae and Anatidae with five species each. Stepwise regression analyses identified wetland area and water level fluctuations as the most important variables determining bird abundance. Variations in species richness were explained by wetland area, shoreline length, vegetation cover and water-level fluctuations. Shoreline development, shoreline length and wetland area lower than one-meter depth were especially important in determining species diversity. Cluster analyses showed similar results. Shoreline length was an important feature influencing total species number, but simple regression analysis showed that the species area relationship occurs in wetlands too. This study concludes that species richness, bird abundance and diversity reach higher values in larger and structurally more heterogeneous wetlands, but with important seasonal dynamics in waterbirds. The relationships between habitat characteristics and community structure did not remain unchanged throughout the year, suggesting that the birds respond differently to one or another habitat characteristic depending on the season. These results show the need for wetland conservation in Chile, paying special attention to the largest and most heterogeneous wetlands to conserve the greatest species richness and bird abundance.

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.

Infection by Contracaecum rudolphii (Nematoda: Anisakidae) in the Neotropic cormorant Phalacrocorax brasilianus, and fishes from the estuary of the Valdivia river, Chile

Seasonal parameters of infection by the nematode Contracaecum rudolphii in the Neotropic cormorant Phalacrocorax brasilianus (Phalacrocoracidae) and their relation with feeding and infection in fishes from River Valdivia, Chile, were determined. The prevalences of infection in birds were similar during seasons, whereas mean intensity and percentages of adult gravid females were higher in spring and summer, respectively. For fishes no seasonal differences were found in infection. Cormorant diet varied seasonally in relation to fish prey consumed and this can be related to seasonal differences in infection parameters of birds. The high infection in birds should be considered as a potential risk for salmoniculture.

Feeding Ecology of the Black-necked Swan Cygnus melancoryphus in Two Wetlands of Southern Chile

The diet of Black-necked swans, Cygnus melancoryphus (Anatidae), was studied in two southern Chilean wetlands in 1993–1995; the Cruces River Sanctuary and the Chihuao-Pichoy River, both near Valdivia. The diet of swans was analyzed by using microhistologic techniques of cell remains in feces collected in the field. The analysis showed that swans were eating predominantly the most abundant submerged aquatic plant, Brazilian waterweed, Egeria densa (Hydrocharitaceae), at both Cruces River (91.9% of diet) and Chihuao-Pichoy River (71.7%). The foraging action of this species was estimated using four forage exclosures in the Chihuao-Pichoy River wetland free from swan grazing, which were compared with foraged controls. Aquatic plant biomass taken in the exclosures was significantly higher (p < 0.05) than biomass sampled outside the exclosures. Cygnus melancoryphus might play an important role as a regulator of aquatic plant biomass, thus contributing to cause a delay in ecological succession. The potential impact of this slowing down is discussed in terms of a natural ecological process in wetland environments.

Threats to a mixed-species colony of Spheniscus penguins in southern Chile

-The Pufiihuil islands, off the coast of Chiloe, southern Chile, have the only known mixed colony of Humboldt (Spheniscus humboldti) and Magellanic penguins (S. magellanicus). Since first reported in 1985, the colony has experienced heavy human disturbance, mainly caused by non-regulated tourist activities and the introduction of domestic goats. On the island closest to shore and most frequently visited by tourists, 28% of dirt burrows have collapsed, mainly by accidental trampling and goat activity. In addition, goats browse the vegetation used by penguins to build their nests. On the island located farthest offshore, with no goats and fewer tourists, only 10% of dirt burrows have collapsed. Comparison with previous population estimates suggests that the colony has declined over the last decade. Considering the important biological value as a mixed colony of Spheniscus penguins, we propose that these islands be officially protected. Received 23 February 1998, accepted 16 May 1998.

Magellanic woodpecker (Campephilus magellanicus) abundance and foraging in Tierra del Fuego, Chile

The Magellanic woodpecker (Campephilus magellanicus) is a vulnerable and poorly studied bird in the sub-antarctic deciduous and evergreen beech (Nothofagus) forests of South America. On Tierra del Fuego island (Chile), we compared Magellanic woodpecker abundance and its foraging habitat in two forest types: pure N. pumilio and mixed forests composed by N. pumilio and N. betuloides, including managed and non managed stands. At a regional scale, abundance of woodpeckers was greater in landscapes including both forest types than in pure N. pumilio landscapes. When both forest types occurred together, woodpecker abundance did not differ between them. The number of trees with foraging signs was correlated with Magellanic woodpecker abundance and was also associated with N. betuloides and snag densities, but was not affected by forest management. Occurrence of pecking on foraging trees was greater in mixed Nothofagus than pure N. pumilio stands. Woodpeckers foraged disproportionately more on larger diameter and more decayed trees. Moreover, trees used for foraging were positively correlated with canopy cover and snag density and were negatively correlated with distance to nearby peatlands and beaver ponds. Direct observation revealed that the flying distance between trees was negatively correlated with proportion of trees with foraging signs. Woodpeckers chose trees that were visited before, suggesting a pattern of tree recognition within foraging territories.

Magellanic Woodpecker (Campephilus magellanicus) sap feeding and its role in the Tierra del Fuego forest bird assemblage

Several woodpecker species feed on phloem-sap flowing from pecked trees. We report sap consumption by the magellanic woodpecker (Campephilus magellanicus) inhabiting beech (Nothofagus) forests of Tierra del Fuego island (Chile). Magellanic woodpeckers drilled sap wells in N. betuloides trees close to their nests and also when they were moving in family groups. Three other bird species were observed foraging and competing for sap: the austral parakeet (Enicognathus ferrugineus) and two small passerines, the patagonian sierra-finch (Phrygilus patagonicus) and the white-crested elaenia (Elaenia albiceps). The abundance of these three bird species was greater in sites around sap wells than in other forest sites, suggesting that magellanic woodpecker is an important species in maintaining the Nothofagus forest bird assemblage.

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.

Nematode parasites of the digestive tract in Neotropic cormorant chicks (Phalacrocorax brasilianus) from the river cruces ramsar site in southern Chile

The neotropic cormorant (Phalacrocorax brasilianus) breeding colony of the Rio Cruces Nature Sanctuary and Ramsar site was surveyed for nematode parasites in southern Chile. Moribund chicks (n=128) of different ages were inspected for anchored nematodes using complete guts. We tested if chicks harbored the same parasites as the adults feeding them. Besides the known Contracaecum rudolphii, third or fourth stage larvae of Pseudoterranova sp. and Anisakis (type I and II) were obtained in this waterbird species for the first time. Most parasites were located in the stomach and C. rudolphii was the dominant species. The prevalence and mean intensity of C. rudolphii infections and the prevalence of Anisakis type I larvae were significantly less (P < 0.05) in the youngest age group of the birds. The prevalence of Pseudoterranova sp. larvae infection was similar among birds of different age. The mean intensity with Pseudoterranova sp. was significantly less (P < 0.05) in younger birds and in Anisakis type I it was similar in different age groups.