Theses and Dissertations - UTB/UTPA

Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Timothy Brush

Second Advisor

Dr. Frank W. Judd

Third Advisor

Dr. Robert I. Lonard


During 1997–99, brood parasitism by the Bronzed Cowbird ( Molothrus aeneus), nest predation, and nest sites were examined in selected songbird species in southern Texas. I found a significantly lower parasitism rate in the Long-billed Thrasher (Toxostoma longirostre ) and Olive Sparrow (Arremonops rufivirgatus) than did Carter (1984) at the same site in the early 1980's. High rates of cowbird visitation to Altamira Oriole (Icterus gularis) nests suggest that cowbirds frequently attempt to parasitize this species. However, orioles probably puncture-eject cowbird eggs from their nests most of the time. Orioles experienced a significantly lower incubation-stage daily nest predation rate (DNPR) than did thrashers and sparrows, and a significantly lower nestling-stage DNPR than did sparrows and Red-winged Blackbirds (Agelaius phoeniceus ). These differences may be explained by oriole nest placement (high, on the tips of branches), which probably keeps the incidence of non-avian nest predation extremely low in orioles. Implications of parasitic behavior, nest predation, nest-site availability, rainfall levels, and nesting biology for host reproductive success are discussed.


Copyright 2000 Christopher R. Hathcock. All Rights Reserved.

Granting Institution

University of Texas-Pan American