Physiological, Behavioral and Reproductive Responses of Black -Capped Vireos and White -Eyed Vireos to Human Disturbance
Hayden, Timothy J.
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https://hdl.handle.net/2142/85361
Description
Title
Physiological, Behavioral and Reproductive Responses of Black -Capped Vireos and White -Eyed Vireos to Human Disturbance
Author(s)
Hayden, Timothy J.
Issue Date
2006
Doctoral Committee Chair(s)
Martin C. Wikelski
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Physiology
Language
eng
Abstract
I conducted research on effects of human activity on a federally-listed endangered bird species, the Black-capped Vireo (Vireo atricapilla ) and a closely related congeneric, the White-eyed Vireo ( Vireo griseus) on Fort Hood Military Reservation, Texas. My research determines effects of human disturbance in wild bird populations by evaluating a variety of response measures at several levels of biological organization including behavioral, physiological, and reproductive variables. In 2001 and 2002, I measured baseline and capture-induced corticosterone levels in white-eyed vireos during the breeding season at sites with heavy military training activities and sites where training activity was restricted on Fort Hood, Texas. Plasma corticosterone concentrations <4 minutes post-capture (baseline) and capture-induced corticosterone concentrations were not significantly different between areas with heavy military training and sites where training was restricted. I quantified nest attendance and song rate in response to repeated human intrusion at nests or approach to singing territorial males of both vireo species in 2003 and 2004. At the first intrusion, mean flush distance of incubating adults was 0.89+/-0.32 (SE) m for Black-capped Vireos (n = 25) and 0.53+/-0.10 m for White-eyed Vireos (n = 27). There was a significant interaction of sex and trial on flush distance in Black-capped Vireos with female flush distance decreasing with repeated trials and male flush distance remaining the same across trials. Song rate of Black-capped Vireos declined with human intrusion during the first two days of disturbance trials, but there was no significant effect on days three and four. White-eyed Vireo song rate had no significant response to human intrusion. I compared reproductive success in a region where restrictions remained in effect during 1997-2003 (control region) and an area where military training activity was restricted in 1997-1999 and unrestricted during 2001-2003. I found significant decreases in the number of young hatched and the number of young fledged from nests where young hatched between periods in the region where training restrictions were lifted in 2001-2003. My results have important implications for endangered black-capped vireo management and protection on Fort Hood and for the efficacy of protective measures for other species of concern.
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