SummaryBased on 21,518 km of road surveys, the Argentinian range of the endangered Saffron-cowled Blackbird Xanthopsar flavus now seems confined to two small and disjunct areas in Corrientes and Entre Rios provinces, north-east Argentina. In Corrientes the species inhabits natural pastures and rice-fields; in Entre Rios agropastoral land. Estimates based on numbers of localities and flock sizes suggest a Saffron-cowled Blackbird population of 500-1,000 individuals. This blackbird is highly gregarious. Mean flock size (n = 30, non-breeding period) was 31.9 birds (range: 6-102), and was significantly larger in Entre Rios. In Corrientes foraging blackbird flocks associated mostly with the Black-and-White Monjita Xolmis dominicana, in Entre Rios with the Brown-and-Yellow Marshbird Pseudoleistes virescens. Nesting in both provinces was colonial, with up to 24 nests in a 0.43 ha plot. Nests were built in native and introduced herbaceous plants. The Shiny Cowbird Molothrus bonariensis parasitized 29.2% of the nests in one colony; its eggs and chicks are larger than those of the host. Plausible reasons for the species's extinction or decline at a local level are drainage of wetlands (south-west Buenos Aires Province) and the replacement of pastures with pine and eucalypt plantations in Corrientes. General threats include trapping for the pet trade and increased cowbird parasitism. Flocks below a minimum size may not be viable. An urgent measure of protection would be the fencing and preservation of traditional colony sites.En base a 21.518 km de censos de rutas parece que la distribution actual del amenazado Tordo Amarillo o Dragon Xanthopsar flavus en Argentina esta limitada a dos pequenas areas disyuntas en las provincias de Corrientes y Entre Rios. En Corrientes la especie se encuentra en pasturas naturales y arroceras, mientras que en Entre Rios usa campos agrfcola-ganaderos. Una estimation basada en el numero de localidades y tamanos de bandadas indicaria una poblacion total de 500 a 1.000 individuos. El tamano promedio de bando (n = 30, periodo no reproductive) fue 31,9 individuos (rango 6-102) y es significativamente mayor en Entre Rios. En Corrientes las bandadas se asocian principalmente con la Monjita Dominica Xolmis dominicana, y en Entre Rios con el Pecho Amarillo Pseudoleistes virescens. La nidificacion fue colonial en ambas provincias, con una densidad de hasta 24 nidos en 0,43 ha. Los nidos se construyeron en plantas herbaceas nativas y exoticas. El Tordo Renegrido Molothrus bonariensis parasito 29,4 % de los nidos de una colonia, siendo sus huevos y polios significativamente mayores. Posibles razones para la extincion y declination a nivel local de la especie serian el drenaje de humedales (SO de Buenos Aires) y el reemplazo de pasturas por bosques implantados de pinos y eucaliptos (Corrientes). Las amenazas a nivel generates incluyen la captura para el Rosendo M. Fraga, Herndn Casanas and German Pugnali 256 comercio de aves de jaula, y un mayor parasitismo de cr-ia. Una medida urgente de protection de l...
SummaryWe 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.
SummaryThe Aguapey river basin in the Pampas grasslands of Argentina is the last refuge for a complete assemblage of globally threatened and Near Threatened birds. We evaluated the influence of landscape characteristics on the occurrence and abundance of six globally threatened and Near Threatened passerines. We used point counts to census birds and vegetation and quantified landscape characteristics 1,000 m from the count centres using remote sensing tools. Strange-tailed Tyrants Alectrurus risora were associated with higher percentages of tall-grass Andropogon lateralis in lowland areas. Saffron-cowled Blackbirds Xanthopsar flavus and Black-and-white Monjitas Heteroxolmis dominicana were associated with rolling landscape with wet lowland grasslands and marshes linked with dry upland grasslands. Marsh Seedeater Sporophila palustris and Chestnut Seedeater S. cinnamomea were associated with tall grasslands and marshes. Rufous-throated Seedeater S. ruficollis was not clearly associated with any type of habitat. The Aguapey grasslands are used mainly for livestock grazing and afforestation. Since 1995, approximately 50% of the original grassland habitat has been planted with exotic trees. If this trend continues, Saffron-cowled Blackbirds are likely to become extinct in the Aguapey river basin which currently supports the largest population of this species in Argentina. We recommend guidelines for establishing future reserves and wildlife management actions based on the landscape responses detected in this study. Future action should consider: maintaining connectivity between the Aguapey grasslands and the Ibera Nature Reserve, creating a protected area, designing a land use plan for the basin, avoiding afforestation in large blocks, removal of government incentives for large afforestation projects, and studying the viability of threatened bird populations in extensive cattle ranching areas.
SummaryThe 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. ResumenEl Macá Tobiano Podiceps gallardoi ha sido recientemente elevado a la categoría de globalmente 'Amenazado' debido a la rápida disminución poblacional sufrida en los últimos 20 años. Distintos factores fueron mencionados como posibles causas, como la depredación de nidos por la Gaviota Cocinera Larus dominicanus, destrucción de colonias por el viento, desecación de lagos y lagunas, etc. Durante la realización de censos en toda el área de distribución del Maca Tobiano en la temporada 2010/11 hallamos un nuevo depredador que nunca había sido mencionado como una posible amenaza, el Visón Americano Neovison vison. Solo un individuo de visón mató 33 adultos de Macá Tobiano y consecuentemente eliminó una de las cinco colonias halladas durante toda la temporada. Dadas las características de las comunidades de aves acuáticas de la zona el impacto de los visones puede llegar a producir una situación catastrófica.
Santa Cruz province is the second largest province in Argentina, and also the least populated. is province makes up the southern tip of continental Argentina. Althought it has low population density and is remote from big cities, in the past it received well-deserved attention from researchers. is was probably due to the presence of many interesting species, among them some threatened, with taxonomic singularities, and/or endemism. e goal of this work is to update knowledge of the distribution and natural history of 21 species from Santa Cruz, including five new to the province.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.