Variable Hawk (Geranoaetus polyosoma) is a Rare Nesting Species in Santa Cruz Province, Southern Continental Patagonia, Argentina

SAGGESE, MIGUEL D.; QUAGLIA, AGUSTIN I. E.; ELLIS, DAVID H.; ELLIS, CATHERINE H.; IMBERTI, SANTIAGO; NELSON, R. WAYNE; CABALLERO, ISABEL C.; TREJO, ANA

JOURNAL OF RAPTOR RESEARCH

RAPTOR RESEARCH FOUNDATION INC

Lugar: Lawrence, Kansas; Año: 2020 vol. 54 p. 447 - 454

0892-1016

In Argentina, the Variable Hawk (Geranoaetus polyosoma) inhabits the northwestern, central, and southern parts of the country, but current information on its breeding distribution and conservation status for most Argentine provinces is lacking. Raptor nest surveys in Santa Cruz Province (southern Argentine Patagonia) during the breeding seasons of 1980-1981 and 2008-2011, revealed six active nests (one in 1980, two in 2008, and three in 2010), plus one additional nest (in 2011) showing evidence of use earlier in the breeding season. Additional ornithological surveys in Santa Cruz Province between 1994 and 2018 revealed two more nests (one each in 2002 and 2004). Results of these combined surveys suggest that the Variable Hawk breeds in very low numbers in the southern continental Patagonian steppes, grasslands, and coastal biomes of Santa Cruz Province. This low density substantiates previous reports on the rarity of the species in this province and contrasts with findings from northeastern Patagonia, where it breeds at high densities. Low Variable Hawk breeding abundance in southern continental Argentine Patagonia is likely related to low prey diversity and abundance as well as anthropogenic activities. We recommend surveys be conducted of this hawk and its prey in different biomes throughout Patagonia.