Notes on Southwestern Costa Rican Birds

Abstract

While engaged in field studies in Costa Rica in 1970 and 1971, I obtained significant distributional and other data on several species of birds in the southwestern portion of the country, i.e., the southern half of the Pacific slope. This report also includes data on specimens collected by Andrew Williams, my field companion in 1971, and by Walter and Elsie Fiala, permanent residents of Costa Rica. All specimens are deposited in the Western Foundation of Vertebrate Zoology collections. Most of my field work was done in the vicinity of Sierpe, a small village located near sea level 13 km S of Palmar Sur, Puntarenas Province. Although the wet lowlands of the Palmar Sur-Sierpe region must have originally supported an impressive primary forest, the area has undergone recent intensive clearing and is now occupied almost entirely by banana plantations, rice fields, pastures, and scattered patches of secondgrowth vegetation. Between 10 June 1971 and 15 November 1972, the Fialas collected birds at their farm, Finca Helechales, 15 km E of Potrero Grande, Puntarenas Province, from elevations of 1000 to 1500 m. Helechales, like surrounding areas, still contains some tracts of relatively undisturbed wet primary forest, although there have been some agricultural and lumbering incursions into the region. A prominent feature of the farm is a brushy savanna, apparently the result of a long history of aboriginal burning; it occupies a large ridge bisecting the essentially forested property. In southwestern Costa Rica, as elsewhere in the American tropics, man's accelerated modification of natural habitats is causing profound changes in the avifauna. Wherever the human population gains access to the forest, whether by newly constructed roads or along natural tributaries, primary habitats are quickly removed and converted to agricultural or other uses. Local extinctions of native forest birds are accompanied by an advance of second-growth species that can circumvent traditional barriers by moving along newly formed corridors of open habitat. It is probable that this corridor effect has made possible recent movements into southern Costa Rica by several of the open country species mentioned here, especially Elanus leucurus (White-tailed Kite), Milvago chimachima (Yellow-headed Caracara), and Leistes militaris (Red-breasted Blackbird). It is reasonable to expect that Leistes and Milvago, presently at their northwestern limits in the Palmar Sur-Sierpe area, will soon move northward into the heavily settled Valle del General. The nomenclature follows that of Eisenmann (1955). Elanus leucurus. White-tailed Kite. Eisenmann (1971) has summarized the recent remarkable range expansion of this species in Middle America. During repeated visits to southwestern Costa Rica between June-August 1964, I did not encounter White-tailed Kites, and the first record for the region was that of Wolf (1966) in June 1965. In 1970 and 1971 the