Ignacio Roesler

Hooded Grebe Podiceps gallardoi population decreased by eighty per cent in the last twenty-five years

We estimated the present population size of the Hooded Grebe Podiceps gallardoi and compared it with the population in 1985. During the breeding seasons 2009/2010 and 2010/2011 we monitored 251 lakes on the main plateaus of Santa Cruz province, southern Patagonia, Argentina, where the entire population of Hooded Grebes spends the breeding season. During 2009/2010 we monitored 131 lakes and observed 521 Hooded Grebes in 16 lakes, while during 2010/2011 we monitored 186 lakes and observed 535 individuals in 14 lakes. At both breeding seasons five lakes contained near 85% of the population. We only observed 6 breeding colonies, two in 2009/2010 and four in 2010/2011, totalling 242 nesting attempts. Nearly 90% of the nests failed during egg stage, mainly due to strong winds and depredation by American mink Neovison vison . Only 28 nests hatched chicks, but none of the young survived to independence due to low temperatures. We compared the results of our 2010/2011 survey with one conducted during 1984/1985 and detected that the population diminished by approximately 80%. This decline was observed on all but one plateau (“Buenos Aires”) where most breeding attempts occurred. Our results show that at present Hooded Grebes are highly dependent on a few suitable lakes where they congregate to breed. We analyse possible causes for the decline of the population and propose conservation actions to protect this species.

A new threat for the globally Endangered Hooded Grebe Podiceps gallardoi: the American mink Neovison vison.

Summary The Hooded Grebe Podiceps gallardoi has been uplisted to globally ‘Endangered’ recently mainly because of the rapid population decline suffered within the last 20 years due to factors such as nest depredation by Kelp Gull Larus dominicanus as well as destruction of colonies by wind and lake desiccation. During a census of Hooded Grebes during the 2010/2011 breeding season we found a new predator that has not previously been mentioned, the American mink Neovison vison. One individual mink killed 33 Hooded Grebes and consequently destroyed one of the five colonies found in that breeding season. Due to the characteristics of the waterbird assemblage in the area, the impact of mink could be catastrophic.

Distribution and habitat use of the Austral Rail Rallus antarcticus and perspectives on its conservation

Summary We present the results of searches for the Austral Rail Rallus antarcticus in Argentine and Chilean Patagonia between January 1998 and February 2006 and from subsequent visits. We surveyed 58 localities and found the rail in 22, which collectively cover approximately 85 km 2 of habitat. A maximum of 175 individuals were detected. This poorly known species was rediscovered in 1998; since then, it has been found in 18 additional localities, providing further data on distribution, habitat and seasonal movements. During the searches, we found that the species faces different threats, such as reduction of wetlands due to cattle grazing, burning and abnormal water management, but also the presence of American mink Neovison vison . However, due to the lack of prior information we conclude that the species should be maintained as Vulnerable.

Abundance and Habitat Use of Nearctic Shorebirds in the Highland Lakes of Western Santa Cruz Province, Argentinean Patagonia

Abstract. Information on Nearctic shorebirds is scarce for inland South America. This work presents information on abundance and habitat use of the species that inhabit water bodies in the highlands of western Santa Cruz province, Argentina. Surveys were conducted during four austral summers (January to March) from 2010 to 2013, with annual data collected at 378 lakes. Results indicate that species distribution varies from year to year. The most abundant species was Bairds Sandpiper (Calidris bairdii). Habitat modeling showed that this species favors ‘depression’ type lakes and that individuals do not distribute uniformly across the area, with higher yearly abundance at Strobel Plateau and the plateaus of the ‘Austral complex’. Size of the water body is positively related to abundance of White-rumped Sandpiper (C. fuscicollis) and Wilsons Phalarope (Phalaropus tricolor). Results show that these highlands are sites of interest for the conservation of migratory shorebirds.

Incubating Upland Goose (Chloephaga picta) differential response to livestock, human, and predator nest disturbance

ABSTRACT The Upland Goose (Chloephaga picta) is a ground-nesting bird that has suffered a precipitous population decline in the last 60 years. We monitored Upland Goose nests with camera traps in Santa Cruz province, Argentina, to study nest disturbances that could reduce reproductive success. We studied female behavior following nest disturbance by predators, livestock, or humans and compared it with situations when females leaving the nests voluntarily. At least 34% of nests were depredated, 92% of them by culpeo (Pseudalopex culpaeus) and gray (Pseudalopex griseus) foxes; only 29% of the monitored nests were successful. Livestock sniffled, licked, and nuzzled the incubating female and the nest contents, and 2 nests were trampled. Off-bout duration was affected by the identity of the intruder. The lengths of predator and human off-bouts were similar and higher than those of foraging and livestock off-bouts. To boost reproductive success, we recommend livestock exclusions and predator control on nesting areas to discourage fox predation. Nests monitoring protocols should include as few and widely spaced visits as possible, restricted to a few people. Given the ecological similarities between the Upland Goose and congeners, including the critically endangered Ruddy-headed Goose (Chloephaga rubidiceps), we extend these recommendations to all Chloephaga spp. breeding areas.

Ruddy-headed Goose Chloephaga rubidiceps : former plague and present protected species on the edge of extinction

The Ruddy-headed Goose Chloephaga rubidiceps has two separate and genetically distinct populations, one sedentary that inhabits the Malvinas/Falklands Islands and another migratory, which inhabits continental southern South America. New information suggests that these populations should be considered as different evolutionarily significant units. The latter population breeds in Austral Patagonia (Argentina and Chile) and overwinters in Central Argentina. It was a very common species in Austral Magellanic steppe grasslands before 1931, when it was declared an “agricultural pest” by the Argentinian government, together with other sheldgeese species. Since then, the continental Ruddy-headed Goose population has declined becoming one of the scarcest species in Austral Magellanic steppe. Nowadays, its population is categorised as critically endangered in Argentina and endangered in Chile. We present data from six road censuses conducted in the breeding areas of Santa Cruz and Tierra del Fuego provinces, Argentina, during 2013–2014 and 2014–2015 (>4600 km, 70 days) and review population trends of the Ruddy-headed Goose since the early 1900s. We counted a maximum of 19 individuals in Santa Cruz and 49 in Tierra del Fuego throughout the breeding season. A literature review indicates that during the last 40 years the size of continental population of Ruddy-headed Goose has been

Amphibians of northwestern Buenos Aires province, Argentina: checklist, range extensions and comments on conservation

Northwestern Buenos Aires province is located within the Pampas region of Argentina. Agricultural practices have extensively modified native grasslands in a relatively short period, leaving no intact pristine areas. Based on data collected between 2006 and 2015 at 153 ponds in agricultural landscapes, we compiled an annotated list of the amphibians of northwestern Buenos Aires province. We report 13 extant species of amphibians, which represent 43% of the known amphibian diversity in Buenos Aires province, and extend the ranges of three species. Three species found only in herpetological collections extend the list to 16 species. Our study is the first long-term survey of amphibians conducted in this part of Argentina and provides valuable information for future conservation actions across agricultural landscapes.

Amphibia, Anura, Hylidae, Scinax granulatus (Peters, 1871): distribution extension in central Argentina

This paper presents novelty information about the distribution of Scinax granulatus in Argentina. These records were made ca. 300 km from the closest known locality. Here we propose that the species is expanding its range following the tree implantation in a former treeless habitat like the Pampas.