Winter Observations of Birds in Oaxaca, Mexico

Abstract

A study of the stratification of birds in forested areas was made in Veracruz and Oaxaca, Mexico, in December, 1957. The largest number of species were observed in low understory. It was found generally that species of large families of birds were spread generally through all the forest strata, perhaps in their manner reducing competition among species. Many notes on color, weight and maturity of birds of many species are recorded. The lowland forests of southeastern Mexico are rich in bird life as shown in papers by Wetmore (1943), Blake (1950), Lowery and Dalquest (1951), and others. Blake (1950: 395) pointed out the continuing need for distributional studies on the avifauna of this region. This need is particularly great because increasing human population is rapidly encroaching on the primitve forest habitats. In December, 1957, the authors crossed the Isthmus of Tehuantepec on the highway from Acayucan, Veracruz, to Salina Cruz, Oaxaca. During the periods December 10-19 and December 21-25 we studied birds in the heavy forests of northeastern Oaxaca at two similar localities (1 mile south of Loseta on the Rio Jaltepec, and at the mouth of the Rio Serabia on the Rio Coatzocoalcos) within 20 miles of Palomares. The primitive state of the tropical evergreen forest is attested to by the fact that tapirs (Tapirella bairdii) and howler monkeys (Alouatta palliata) were present and not uncommon. It is the purpose of this paper to present information on the composition and distribution of the avifauna of a tropical forest in winter. Data from our observations are summarized in an annotated list of all species encountered in the forest only and in two tables showing the relative frequency of observation and netting of understory birds (table 1) and the observed composition of the winter fauna and its distribution in the forest (table 2). Allee (1926) studied the distribution of several classes of animals in a rain forest in Panama, but there is relatively little information available for birds.