Birds of a Highland Clearing in Cundinamarca, Colombia

Abstract

SEVERAL authors (Dugand 1947, Olivares 1969, Lehmann 1970) have noted effects on distribution of Colombian avifauna by land disturbance, particularly the ever-accelerating clearing of forest to make way for pasture and agriculture. This paper attempts to describe this process on a small ranch near the capital city of Bogota', which has been settled for more than a century and where, consequently, the altered ecology has more or less stabilized. The Finca Rancho Grande (40 36' N, 740 20' W), is situated 15 km west of Bogot'a in Santandercito, Cundinamarca, in the valley of the Bogot'a River, a tributary of the Magdalena, Colombia's principal river. The finca lies 8 km downriver from the famous Tequendama Falls, which mark one of the bounds of the altiplano. The finca's altitude, 1700 m, is thus considerably lower than that of the Sabana of Bogota (2600 m). Meyer de Schauensee (1964) defines the tropical zone as extending from 0 to 1385-1700 m, and the subtropical zone as going from the 1385-1700 m line to 2300-2600 m. This finca is at the altitude of overlap between the two zones. The avifauna consists mainly of tropical and subtropical species of the west slope of the Eastern AndesMagdalena Valley. So far 82 species of birds have been seen at the finca, 10 North American migrants and 72 residents in Colombia. The finca, roughly 500 m by 500 m (25 ha or 61.8 acres) in extent, lies on the north-facing slope of the east-west running valley. It is a stepsided valley, with approximately flat shelves alternating with grades as steep as 400, descending northward to the river, some 1.5 km away at a level of 1500 m. Almost the entire valley on both sides of the river, originally forested, has been converted into fincas for animal husbandry (cattle and horses) and orchards for coffee culture, with numerous small towns and weekend cottages built to take advantage of the pleasant climate (temperature 16.5?-24? C; 62?-75? F). Behind the finca, to the south, climbs the Cordillera Subia with peaks as high as 2800 m, and separating the valley of the Bogota' River from that of the Subia River. Much of this cordillera, parts of which were explored by the Chapman party in 1910-15 (Chapman 1917-), has, like the region around Santandercito, been cultivated for at least 100 years, but considerable stands of thick secondary humid forest (Cecropia, tree fern, tree-sized Melastomataceae Miconia) still remain around swamps. On hillsides too steep for human use (grades of at least 700)