The Influence of Nest Site Characteristics on Nest Success and Parasitism of Black-capped Vireos (Vireo atricapilla) in the Southwestern Edwards Plateau




Mulhall, Brendan

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The Black-capped Vireo (Vireo atricapilla) was delisted from the U.S. Endangered Species List by the United States Fish and Wildlife Service (USFWS) in 2018. As part of the USFWS Post-Delisting Monitoring Plan, nest searching and monitoring of vireo nests were completed in 2021 and 2022 to provide an estimate on parasitism and nest success in the region. Field work for this study took place in Kickapoo Cavern State Park in the western Edwards Plateau of Texas. The two field seasons were characterized by mild drought conditions in 2021 and exceptional drought conditions in 2022. The logistic exposure method was used to quantify the relative success vireo nests had in each year. Nests found in 2021(n = 18) had a daily survival rate (DSR) of 0.96 and an overall chance of survival from nest building to fledging of 40.5%. Nests found in 2022 (n = 15) had a DSR of 0.88 and an annual survival rate of 4.6%. Additionally, in 2021 vireos only nested in Ashe Juniper (Juniperus ashei) 16% (n = 3) of the time while in 2022 juniper was utilized in 46% (n = 7) of nests. This is of particular importance because juniper removal is one method used to help enhance potential Black-capped Vireo habitat. Black- capped Vireo nests were parasitized by Brown-headed Cowbirds 33% (n = 6) and 47% (n = 7) of the time in 2021 and 2022, respectively. The results of this study will help inform management decisions for Black-capped Vireo populations as historic drought conditions likely become more common under changing global climates.



avian, ecology, conservation, ornithology


Mulhall, B. (2023). The influence of nest site characteristics on nest success and parasitism of black-capped vireos (Vireo atricapilla) in the southwestern Edwards Plateau (Unpublished thesis). Texas State University, San Marcos, Texas.


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