Structure of the avifauna during the winter-spring season in Estero Rancho Bueno, Baja California Sur, México

Abstract

PERIODIC SURVEYS WERE CONDUCTED FROM NOVEMBER 1993 TO JUNE 1994 IN ESTERO RANCHO BUENO, A MANGROVE LAGOON ENVIRONMENT ON THE WEST COAST OF BAJA CALIFORNIA SUR. WE FOUND 5,65 BIRDS (56 SPECIES). THE AVIFAUNA INCLUDED 31 RESIDENT, 22 MIGRATORY, AND 3 SPECIES OF UNDETERMINATED MIGRATORY STATUS. MOST OF THE SPECIES WERE COASTAL AND ESTUARINE BIRDS; HOWEVER THERE WERE SOME TERRESTIAL AND WIDE-RANGING BIRDS. THERE IS EVIDENCE THAT AT LEAST 2 SPECIES BREED IN THE AREA; 4 SPECIES ARE PROTECTED BY MEXICAN LAW AND 5 SPECIES HAVE COMMERCIAL VALUE. DIFFERENT INDICES SHOW THAT THE BIRD COMMUNITY DIVERSITY IS LOWER BY THE END OF SPRING AND THE DOMINANCE OF THE BROWN PELICAN (PELECANUS OCCIDENTALIS), THE WESTERN GULL (LARUS OCCIDENTALIS), AND THE RING-BILLED GULL (L. DELAWARENSIS) INCREASES IN THIS TIME OF THE YEAR. COMPARISON OF SPECIES RICHNESS BETWEEN AREAS WITH AND WITHOUT MANGROVE HABITAT INDICATES THAT EQUITY IS HIGHER IN AREAS WITH MANGROVE.