干旱区生态环境知识资源中心

Worthen’s Sparrows (Spizella wortheni) are endemic to the Mexican Plateau and have been listed as globally endangered. The breeding biology of these sparrows is poorly understood, and nesting is only known to occur at three locations (Las Esperanzas, Nuevo Leon, and La India and Tanque de Emergencia, Coahuila). In June and July 2006, we searched for nests of Worthen’s Sparrows and located three new breeding localities: La Carbonera and San Rafael in the state of Nuevo Leon, and San Jose del Alamito in the state of Coahuila. We subsequently sampled vegetation where nests were located and, on 26 August 2006, conducted surveys along 1-km transects at the three new breeding locations as well as at El Erial-La Casita, Nuevo Leon. We recorded the most Worthen’s Sparrows at El Erial-La Casita (N = 33), followed by San Jose del Alamito (N = 9), San Rafael (N = 6), and La Carbonera (N = 3). No nests were located at El Erial-La Casita, but small groups of sparrows that included juveniles were observed. At the three breeding locations, shrub strata were dominated by tarbush (Flourensia cernua; San Jose del Alamito and La Carbonera) and Berlandier’s wolfberry (Lycium berlandieri; San Rafael). Most (68%) recently recorded nests for this species have been found in tarbush. Historical and recent data (including our study) suggest that Worthen’s Sparrows typically breed in grassland habitat where shrubs of some type are also present. Because conversion of land to agriculture continues to be a major threat to grasslands in northeastern Mexico, we recommend that conservation efforts be implemented to protect the known breeding areas of Worthen’s Sparrow.