Avifauna of the Río San Juan Basin, Guerrero, Mexico

Abstract

WE PRESENT AN ANALYSIS OF THE SPECIES RICHNESS AND ABUNDANCE OF BIRDS AT SEVERAL LOCALITIES OF THE RÍO SAN JUAN BASIN, IN GUERRERO STATE, AN AREA BELONGING TO THE BALSAS BASIN BIOTIC PROVINCE. FIELD WORK WAS PERFORMED FROM JUNE 2001 TO SEPTEMBER 2002. 164 SPECIES WERE RECORDED, WITH SOME OBSERVATIONS REPRESENTING RANGE EXTENSIONS. THE SPECIES RICHNESS WAS SIGNIFICANTLY HIGHER IN TROPICAL DECIDUOUS FOREST, WHICH ALSO HAD THE GREATEST NUMBER OF SPECIES RESTRICTED TO A SINGLE VEGETATION TYPE. 72% OF THE SPECIES ARE RESIDENTS AND THE 28% REMAINING ARE MIGRATORY. A MAJOR PROPORTION OF THE SPECIES ARE RARE (37.5%) AND UNCOMMON (38.2%), IN CONTRAST TO THOSE THAT ARE ABUNDANT (2.12%) AND COMMON (3.5%). THE ENDEMISM IN THE REGION IS HIGH, WITH 28% OF THE SPECIES ENDEMIC TO MEXICO. SIX SPECIES ARE CONSIDERED THREATENED.