This paper reports the richness of bird species in the northeastern region of the Sierra Nevada mountains, Mexico, from August to November 2001 and from February to June 2002. A total of 104 species representing 34 families and 11 orders were recorded, of wish 88 were resident and 16 were migrants. Forty percent of the species were abundant, 22% scarce, and 38% rare. The richest families were Parulidae (13 species), Emberizidae (11) and Turdidae (9). Sixty-five species were considered core and 39 vagrant. This study adds 43 species to the inventory for this region of the state of Mexico.
