LAMBERTUCCI Sergio Agustin
congresos y reuniones científicas
Black-chested Buzzard-eagle Population Trends in Patagonia and the Possible Relationship with its Main Food Source
IGNAZI, G.O.; TREJO A.; HIRALDO, F.; DONÁZAR, J. A.; SANCHEZ-ZAPATA, J.A.; LAMBERTUCCI, S. A.
Congreso; I Worldwide Raptor Conference; 2013
Long term studies of long lived species of raptors constitute an important tool for understanding demographic variation and conservation efforts. Such studies are more relevant if they can be compared to variability in food sources. The Black-chested Buzzard-eagle (Geranoaetus melanoleucus) is a large raptor inhabiting open areas of South America. To date, no studies about its population trends have been undertaken. Here we present the first study of long term Buzzard-eagle population changes, analyzing abundance and age class proportions throughout a period of 20 years. We conducted morning and evening counts of Buzzard Eagles at 21 points surrounding Junín de los Andes, north-west of Patagonia, during the breeding seasons of 1992, 2006, 2011 and 2012. At each count site we estimated the relative abundance of the Buzzard-eagles most important prey, the European hare (Lepus europaeus), by conducting 30 minute foot transects. The number of eagles decreased from 59 in 1992, to 37 in 2006, 33 in 2011, and 29 in 2012. Forty one percent of eagles observed in 1992, and 27% in 2006 were juveniles, while in 2011 and 2012 no juveniles were observed. We found similar tendencies of decrease in the presence of hares. The decreasing abundance of juvenile eagles may be related to the decrease in the number of hare in the area. Whether juvenile individuals are dispersing to other areas with greater prey availability, or if their mortality has increased in the area is unknown. We hypothesize that ash deposition from the eruption of Puyehue volcano in June 2011 may have produced a bottom up effect on the eagles. Specifically, we propose that deposition of volcanic ash reduced vegetation, which suppressed hare populations, and subsequently indirectly affected eagle populations.