Distribution and abundance of Chubut Steamerducks: an endemic species to Central Patagonia, Argentina

Abstract

SummaryWe documented the breeding distribution and estimated abundance of Chubut Steamerducks Tachyres leucocephalus, a flightless waterbird endemic to a relatively small section of coastline in Patagonia, Argentina. The distribution of Chubut Steamerducks is restricted to approximately 700 km of coast. We counted 1,703 adult steamerducks at a subset of shorelines within their range and estimated 1,841 adults after correcting for visibility for shore-based surveys. To estimate adult densities in unsurveyed areas, we used two different methods of extrapolation, resulting in estimates of 1,587 and 1,832 adults. Combined with numbers from surveyed shorelines, the total breeding population size is estimated to be between 3,428 and 3,673 adults. In addition, we counted 1,899 juvenile steamerducks, which occur in irregular aggregations. The Interjurisdictional Marine Park in San Jorge Gulf contains about 46% of the entire population, which may provide some protection from disturbance and habitat destruction. However, oil pollution, other anthropogenic activities, and invasive species still pose potential threats to the population. ResumenHemos documentado el rango de distribución y estimado el tamaño poblacional del pato vapor cabeza blanca Tachyres leucocephalus, un ave acuática no voladora endémica de una estrecha sección costera de Patagonia, Argentina. La distribución del pato vapor cabeza blanca esta restringida a aproximadamente 700 km de costa. Hemos contado 1,703 individuos a lo largo de sectores costeros discretos dentro de su rango de distribución, y estimado un total de 1,841 adultos luego de aplicar los correspondientes factores de corrección. Para estimar la densidad de adultos en los sectores no relevados, hemos utilizado dos métodos diferentes de extrapolación, resultando en un número estimado de 1,587 y 1,832 adultos. De esta forma, al sumar individuos relevados y estimados, el tamaño poblacional oscilaría entre los 3,428 y 3,673 adultos reproductores. Asimismo, hemos contado un total de 1,899 juveniles de pato vapor cabeza blanca, los cuales ocurren en agregaciones regulares. El Parque Interjurisdiccional Marino Golfo San Jorge alberga alrededor del 46% de la población, lo cual podría representar una medida de protección frente a disturbios o destrucción del hábitat. Sin embargo, la contaminación por hidrocarburos y otras actividades de orígen antrópico junto con la introducción de especies, representan un potencial peligro para la población completa.

Stomach nematodes of three sympatric species of anatid birds off the coast of Patagonia

“…Of the species studied here, two are residents: the Chubut steamer duck, Tachyeres leucocephalus (Humphrey and Thompson, 1981), and the crested duck, Lophonetta specularioides (King, 1828), while the black-necked swan, Cygnus melancoryphus (Molina, 1782) is a partial neotropical migrant. Tachyeres leucocephalus is a flightless marine endemic bird that lives along a small section of the Patagonian coastline in Argentina (Agüero et al, 2012), and it breeds in syntopy with L. specularioides on the northern San Jorge Gulf, Chubut. On the other hand, C. melancoryphus dwells in freshwater and brackish-water marshes.…”

Variation in the size of eggs of Chubut Steamer Ducks (Tachyeres leucocephalus)

“…We surveyed 337 km of mainland coast and 104 km of island coast throughout the distribution of Chubut Steamer Ducks looking for nests (Fig. 1), from Playa Unión, Rawson (43 21 0 S, 65 03 0 W) to the Chubut-Santa Cruz provincial border (46 00 0 S, 67 36 0 W; for details, see Agüero et al 2011). Nests were found from Punta Tombo (44 03 0 S, 65 12 0 W) to the Vernaci Islands (45 11 0 S, 66 30 0 W; Fig.…”

“…Chubut Steamer Ducks (Tachyeres leucocephalus) are flightless marine waterfowl endemic to a 700-km section of coast of Chubut Province, Central Patagonia, Argentina; the total population is <3700 individuals (Humphrey and Thompson 1981;Agüero et al 2010Agüero et al , 2011. The species is classified as near threatened globally (BirdLife International 2011;IUCN 2011) owing to the combination of its restricted distribution, small population size, flightlessness and the potential threats to which it is exposed (see Agüero et al 2011). Despite this, there is little knowledge of its basic ecology.…”

Incubation pattern of endangered Chubut Steamerduck (Tachyeres leucocephalus) and environmental features: implications for conservation

“…In particular, Chubut Steamerducks are endemic to a 700-km section of coast of Chubut Province, Patagonia, Argentina; with an estimated total population of 3,500 adults and a minimum of 2,000 juveniles (Agüero et al 2012). Owing to the combination of its restricted distribution, small population size, ightlessness and the potential threats to which it is exposed, this specie has been recently listed as "Vulnerable" on the IUCN Red List of Threatened Species (IUCN 2022).…”

“…Owing to the combination of its restricted distribution, small population size, ightlessness and the potential threats to which it is exposed, this specie has been recently listed as "Vulnerable" on the IUCN Red List of Threatened Species (IUCN 2022). The Interjurisdictional Marine Park in San Jorge Gulf contains about 46% of the entire population of Chubut Steamerducks (Agüero et al 2012) and may provide some protection from human disturbance and habitat destruction within its jurisdiction. However, there are other potential threats to Chubut Steamerducks that marine park designation does not protect against, like oil spill and introduction of invasive species.…”