Aves Argentinas Asociacion Ornitologica del Plata

Buenos Aires, Argentina

Aves Argentinas Asociacion Ornitologica del Plata

Buenos Aires, Argentina
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Barnett J.M.,Aves Argentinas Asociacion Ornitologica Del Plata | Roesler I.,University of Buenos Aires
Bird Conservation International | Year: 2014

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 km2 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. © BirdLife International 2013.

Roesler I.,University of Buenos Aires | Casanas H.,Aves Argentinas Asociacion Ornitologica Del Plata | Mahler B.,University of Buenos Aires | Reboreda J.C.,University of Buenos Aires
Bird Conservation International | Year: 2012

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 Airesa) 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. © 2011 BirdLife International.

Roesler I.,University of Buenos Aires | Casanas H.,Aves Argentinas Asociacion Ornitologica Del Plata | Volpe N.,Aves Argentinas Asociacion Ornitologica Del Plata
Bird Conservation International | Year: 2012

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. © 2011 BirdLife International.

Di Giacomo A.S.,University of Buenos Aires | Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica Del Plata | Kliger R.,University of Buenos Aires | Reboreda J.C.,University of Buenos Aires | And 2 more authors.
Bird Conservation International | Year: 2015

The Strange-tailed Tyrant Alectrurus risora (Aves: Tyrannidae) is an endemic species of southern South American grasslands that suffered a 90% reduction of its original distribution due to habitat transformation. This has led the species to be classified as globally Vulnerable. By the beginning of the last century, populations were partially migratory and moved south during the breeding season. Currently, the main breeding population inhabits the Iberá wetlands in the province of Corrientes, north-east Argentina, where it is resident all year round. There are two remaining small populations in the province of Formosa, north-east Argentina, and in southern Paraguay, which are separated from the main population by the Parana-Paraguay River and its continuous riverine forest habitat. The populations of Corrientes and Formosa are separated by 300 km and the grasslands between populations are non-continuous due to habitat transformation. We used mtDNA sequences and eight microsatellite loci to test if there were evidences of genetic isolation between Argentinean populations. We found no evidence of genetic structure between populations (ΦST = 0.004, P = 0.32; Fst = 0.01, P = 0.06), which can be explained by either retained ancestral polymorphism or by dispersal between populations. We found no evidence for a recent demographic bottleneck in nuclear loci. Our results indicate that these populations could be managed as a single conservation unit on a regional scale. Conservation actions should be focused on preserving the remaining network of areas with natural grasslands to guarantee reproduction, dispersal and prevent further decline of populations. © 2014 BirdLife International.

Vizentin-Bugoni J.,University of Campinas | Areta J.I.,CONICET | Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica Del Plata | Di Giacomo A.S.,University of Buenos Aires | And 4 more authors.
Bird Conservation International | Year: 2013

The Marsh Seedeater Sporophila palustris is one of the most endangered and least known of the capuchino seedeaters. Breeding populations are patchy, occurring in north-east Argentina, southern Brazil, and Uruguay. We present data on the breeding biology of the species, and describe nests and eggs, behaviour (including courtship, nesting, incubation and parental care), breeding sites and food items. Marsh Seedeaters breed in well-preserved grasslands with wet soils and tall vegetation. In general, these habitats are used for extensive livestock ranching. Main threats are overgrazing, widespread use of fire, conversion of grasslands to pastures of exotic grasses and rice fields, afforestation, and illegal trapping. Most breeding sites are located in Important Bird Areas, but only one in Brazil and one in Argentina are protected. We propose a series of actions to promote the conservation of Marsh Seedeaters and other endangered birds that coexist in grassland habitats. Copyright © BirdLife International 2013 Â.

Lopez-Lanus B.,Pacheco de Melo 2534 | Ornstein U.,Aves Argentinas Asociacion Ornitologica del Plata | Olarte L.G.,ATA Fondo Filantropico | Raggio J.,Aves Argentinas Asociacion Ornitologica del Plata
Hornero | Year: 2012

We examined the similarity in the vocalizations of Porzana spiloptera and Laterallus jamaicensis. Both species have a similar vocal repertoire and their songs are very similar in the structure of the notes. Vocalizations of both species could be confused in the field due to their timbre and structure, but their songs are distinctive by the number of high-pitched notes that precede the final low note. The song of Porzana spiloptera is more similar to the song of the North American and Caribbean subspecies of Laterallus jamaicensis than to the song of the South American subspecies. We compared the songs of both species with the song of an individual found in western Río Negro Province previously considered to be Laterallus jamaicensis. The song is indistinguishable from that of Porzana spiloptera and different from that of Laterallus jamaicensis salinasi, thus we concluded that it belongs to Porzana spiloptera.

Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica Del Plata | Di Giacomo A.S.,Genetica y Evolucion | Reboreda J.C.,Genetica y Evolucion
Bird Conservation International | Year: 2011

The north-east of Argentina contains a high number of globally threatened grassland birds and is increasingly managed for livestock, with annual burning in remaining natural grasslands. The Strange-tailed Tyrant Alectrurus risora, a globally threatened grassland specialist, has suffered a 90% contraction in its original range. From 1996 to 2008 we monitored a breeding population in Formosa, north-east Argentina, and explored the effect on breeding of four accidental and one prescribed fires. The plant most frequently used for nesting was Imperata brasiliensis, but the frequency of use was lower after a fire than before. In years with a fire, the height of the plant used for nesting and the height of the nest were lower than in those without a fire. Females avoided nesting in the burned plot in the breeding season immediately after the prescribed fire, but they started to return to the burned plot by the second breeding season and did not discriminate between plots by the third breeding season after the fire. Movements of females after the prescribed fire did not affect nest survival, clutch size, hatchability or chick survival indicating this species was adapted to regular fires. However, our results also show that annual burning in the grassland negatively affects the settlement for reproduction of Strange-tailed Tyrants and that the intervals between burns in the same grassland should be longer than two years. © 2011 BirdLife International.

Facchinetti C.,University of Buenos Aires | Mahler B.,University of Buenos Aires | Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica Del Plata | Reboreda J.C.,University of Buenos Aires
Condor | Year: 2011

In some sexually dichromatic passerines, juvenile males retain a plumage similar to that of adult females through their first year or longer (delayed plumage maturation). The Tawny-bellied Seedeater (Sporophila hypoxantha) is a sexually dichromatic species in which, to the human eye, the juveniles look like females. We analyzed the species' stages of plumage maturation by reflectance spectrometry and a visual model of color discrimination on captive individuals of known ages. We found that males retain a plumage different from that of adult males through their first breeding season. By the time males passed the age of 1 year, their color did not differ from that of adult males in any region of the body except the crown. Spectrophotometry also revealed differences between the plumage color of juvenile males and females, and the color-discrimination model implies that the birds should be able to detect these differences. Thus juvenile males of the Tawny-bellied Seedeater acquire adult plumage after their first breeding season but are already dichromatic during the first year. How this pattern of plumage development affects the species' reproductive or other social behavior deserves further study. © The Cooper Ornithological Society 2011.

Mahler B.,University of Buenos Aires | Lopez N.I.,University of Buenos Aires | Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica del Plata | Reboreda J.C.,University of Buenos Aires
Ibis | Year: 2010

The Shiny Cowbird Molothrus bonariensis is a sexually dichromatic species, in which males have blackish-blue iridescence and females are dull brown. However, in some subtropical parts of its distribution, females show a plumage polymorphism that ranges from dull brown to dark brown and even black. Plumage melanization has been shown to protect feathers from bacterial degradation, decreasing the effects of harmful bacterial activity and thus plumage damage. In this study, we assessed whether bacterial feather-degrading activity is acting as the selective force to increase darkness in the plumage of the female Shiny Cowbirds in Argentina. We compared the degradation of female Shiny Cowbird feathers belonging to different colour morphs when exposed to bacterial strains isolated from subtropical and temperate zones of its distribution, as well as to Bacillus licheniformis. We did not find differences in susceptibility to bacterial degradation between brown feathers and darker feathers. These results suggest that female plumage polymorphism in Shiny Cowbirds has not arisen as a defence against bacterial feather-degrading activity. © 2010 The Authors. Journal compilation © 2010 British Ornithologists' Union.

Di Giacomo A.S.,University of Buenos Aires | Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica Del Plata | Reboreda J.C.,University of Buenos Aires
Condor | Year: 2011

The Strange-tailed Tyrant (Alectrurus risora) is an endangered obligate grassland bird that inhabits savannas, wet grasslands and marshes in southern Paraguay and northeastern Argentina. We evaluated the extent of social polygyny, main measures of reproduction (clutch size, hatching success, and chick survival), and factors that influence nest success in this species. We also estimated the reproductive success of females and males by measuring the number and fate of nesting attempts by banded females and the number of females per a male's territory. More than 80% of the males were polygynous. Males defended contiguous territories of 2-2.5 ha that included the territories of up to four females. Females built the nest, incubated the eggs, and brooded and fed the chicks. On average, successful nests fledged 2.3 chicks. Nest survival over the entire cycle was 0.23 and decreased with nest age and time of breeding. Most females made two or three nesting attempts per breeding season and bred in the same area for 2 or 3 consecutive years. In contrast, males rarely were seen in the same area more than 1 year, suggesting sexual differences in mortality. As a result of this, the reproductive succcess of females and males was similar. Our findings indicate that although males are highly polygynous and nest success is low, the high turnover of males in successive breeding seasons and the high probability of females' renesting within and in successive breeding seasons reduce the variance in reproductive success of both sexes. © The Cooper Ornithological Society 2011.

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