North American Migrants in the Sierra de Tuxtla of Southern Veracruz, México

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Abstract
The Sierra de Tuxtla, an isolated volcanic mountain range in southern Veracruz, Mexico, occupies a geographic position favorable for the occurrence of many North American birds that normally migrate through the Gulf coastal plain. The Sierra''s low relief and the generally parallel alignment of its major peaks with the coastline prevent it from acting as a barrier to most migrants. A variety of humid and drier habitats in the Sierra provides suitable conditions for many migrants. The majority of land-bird migrants frequent forest edge, thickets, and semi-open places in preference to the unbroken forest which covers many of the peaks and much of the Gulf-facing slopes. Although the 2 large water bodies, Lake Catemaco and Bahia Sontecomapan, do not possess extensive marsh habitat, they attract some migrant water and marsh birds. Northers in late winter and early spring cause concentrations of some water and land-bird transients, but the birds tend to disperse more in the autumn when there are usually less severe weather disturbances. Hawks take advantage of the updrafts over the Sierra, and large flights occasionally occur in spring. High densities of small passerines occasionally occur, and the number of migrants passing through the Sierra can be compared favorably with the number moving through areas of similar size in central and eastern United States. One hundred and thirty-one spp. of migrant birds have been reported from the Sierra de Tuxtla and coastal areas of its base. Information on abundance in the Sierra is supplied for many of the 67 spp. in the selective annotated list. Three spp. are believed to be new for Veracruz. New seasonal dates and some earlier and later spring and autumn migration dates than have heretofore been published for later spring and autumn migration dates than have heretofore been published for migrants in Veracruz are given for 26 spp. Six spp. have apparently not been previously recorded in Veracruz outside of the west-central mountains, and records are included of at least 15 spp. for which there have been few reports in the state.