NESTING ECOLOGY OF THE NORTHERN BEARDLESSTYRANNULET (CAMPTOSTOMA IMBERBE) IN THE LOWER RIO GRANDE VALLEY OF TEXAS, U.S.A.

Abstract

During 2002–2003, we studied the breeding ecology of the Northern Beardless-Tyrannulet (Camptostoma imberbe), a poorly known and rare permanent resident in the Lower Rio Grande Valley of Texas, United States of America. We found 28 nests in clusters of Spanish moss (Tillandsia usneoides) or ball moss (T. recurvata), 93% of which were in cedar elm (Ulmus crassifolia) trees. Nest-building, incubation, and nestling periods averaged 7.0, 14.0, and 18.5 days, respectively. Of the 28 nests, 43% were successful, while 38% of the failed nests showed obvious signs of depredation. Nests were located in areas with denser Tillandsia growth and with taller trees than nearby non-used areas. Availability of this habitat may limit the population size of Northern Beardless-Tyrannulets in the Lower Rio Grande Valley.