¿Puntos fijos o recorridos lineales para el censo de aves en la estepa patagónica?

ALEJANDRO TRAVAINI; JAVIER BUSTAMANTE; JUAN JOSÉ NEGRO; RUBÉN DARÍO QUINTANA

ORNITOLOGIA NEOTROPICAL

The Neotropical Ornithological Society

Año: 2004 vol. 15 p. 513 - 525

1075-4377

Abstract. – Point or transect counts as alternatives to censusing steppe birds in Patagonia. – Success-ful evaluation of bird populations in Patagonia depends on the appropriate choice and use of survey meth-ods. Our objective was to evaluate three bird survey methodologies: point counts, foot transects, and road transects, for bird distribution evaluation (particularly birds of prey) in shrub-steppe landscapes of south-ern Patagonia. Field work was undertaken during the spring of 1998 and 1999 in Santa Cruz province, southern Argentine Patagonia. We performed 15-min point counts, 30-min foot transects and vehicle road transects at 40–60 km/h. During the 1998 spring, we contacted 65 raptors representing 8 species during 125 point counts. We also contacted 252 raptors (10 species) during 3537 km of road transects. Road transects produced 22 times more contacts per unit effort than did point counts. During spring 1999, we contacted 2065 individuals, representing 54 species of birds. Foot and road transects provided significantly more contacts than point counts, both for raptors and all species of birds. Although more raptors were contacted by road census, foot transects performed well for all other species of birds. The detection and identification of birds by foot transects were less affected by prevailing wind conditions, and contact rate was higher than that of point counts on a time effort basis.Success-ful evaluation of bird populations in Patagonia depends on the appropriate choice and use of survey meth-ods. Our objective was to evaluate three bird survey methodologies: point counts, foot transects, and road transects, for bird distribution evaluation (particularly birds of prey) in shrub-steppe landscapes of south-ern Patagonia. Field work was undertaken during the spring of 1998 and 1999 in Santa Cruz province, southern Argentine Patagonia. We performed 15-min point counts, 30-min foot transects and vehicle road transects at 40–60 km/h. During the 1998 spring, we contacted 65 raptors representing 8 species during 125 point counts. We also contacted 252 raptors (10 species) during 3537 km of road transects. Road transects produced 22 times more contacts per unit effort than did point counts. During spring 1999, we contacted 2065 individuals, representing 54 species of birds. Foot and road transects provided significantly more contacts than point counts, both for raptors and all species of birds. Although more raptors were contacted by road census, foot transects performed well for all other species of birds. The detection and identification of birds by foot transects were less affected by prevailing wind conditions, and contact rate was higher than that of point counts on a time effort basis.