Research Objectives:

1. Identify the nest predators for black-capped vireos (Vireo atricipilla), [BCVI]  and white-eyed vireos (Vireo griseus) [WEVI] on multiple public and private lands in southwest and central Texas.
   
   
2. Identify the temporal and spatial predator activity of potential BCVI and WEVI nest predator species within the central TX study area.
   
   
3. Examine the correlation between vegetation characteristics and nest predators
   
   
4. Determine the relationship between nest predation and  parasitism by brown-headed cowbirds (BHCO)

Management Implications:

1. This study will provide additional information regarding the nest predator assemblage, predator foraging patterns, and abundance of nest predators for BCVI and WEVI in the region.  Understanding which potential predator species are present, how the predator numbers change through time, and how these spatial-temporal dynamics might relate to nest predation within the region is essential to future management efforts for endangered species.
   
   
2. The majority of nest predator research on BCVI has been conducted on public lands within a small region of the species’ range.  Since 95% of land in Texas is privately owned, the majority of BCVI habitat management must occur on these private lands.  As a result, it is important to conduct research on these properties to determine if previously completed research on public lands is applicable to private properties. If private land management practices (ranching, predator culling, etc) affect nest predator assemblages or activity patterns then nest failure due to predation may be altered, and alternative management plans may need to be considered.
   
   
3. This study also aims to increase our knowledge of nest predator species by collecting data from multiple locations across the range of the BCVI. As a result, this nest predator research will further our understanding of black-capped vireo and white-eyed vireo nest predator assemblages and provide important knowledge to increase the effectiveness of future management directed at recovery of the endangered black-capped vireo.

Project Summary:

Predation is a primary limiting factor of nest success, including for endangered black-capped vireos (Vireo atricapilla), and sympatric white-eyed vireos (Vireo griseus) that breed in central and southwest Texas. I investigated predator assemblages in black-capped vireo and white-eyed vireo habitat and identified primary nest predators throughout the black-capped vireo range in 2008 and 2009. Study areas were located on private lands in Coryell, Hamilton, and Bosque Counties, Texas, and State-managed public lands at Kerr Wildlife Management Area (Kerr County, Texas), and Devils River State Natural Area (Val Verde County, Texas-2009 only).

We identified breeding pairs of both WEVI and BCVI and obtained nest locations through observations and systematic searching.  If nesting BCVI were not present in the patch, we conducted nest searching solely for WEVI.  For black-capped vireo nests at all study sites and a subset of white-eyed vireo nests on private lands, I used continuous recording digital video cameras with infrared to identify nest predators and nest fate.  We placed cameras1-2m from nest location and utilized a 15-m cable to connect camera to the DVR and 12-v battery, which allowed for minimal nest disturbance during battery changes.  We visited properties every 2–3 days to replace data cards and batteries as needed and left cameras in place until the nest fledged or failed.  We also collected at-nest vegetation data to identify nest substrate species, nest concealment, vegetation height, visual obstruction, and distance to edge at the end of each season.   
To determine predator activity, we sampled a subset of WEVI and BCVI nests on private lands in Coryell county using bait stations with infrared game cameras and a large funnel trap for sampling the herptofaunal population.  We also conducted avian point counts at active nests (in 2009) to sample for potential avian predators.