06/05/2026
On this World Environment Day, we are highlighting some neat field work from the Oklahoma Biological Survey!
Dr. Jeremy Ross, OBS Ornithologist, and his team have been busy this field season with surveys for the Black-Capped Vireo in southwestern Oklahoma. This little migratory bird overwinters in Southern Mexico and returns each year to north-central Mexico, Texas, and Oklahoma to breed. Black-Capped Vireos are extremely picky about nest sites, typically selecting small deciduous trees in successional sloped landscapes. Male Black-Capped Vireos are extremely aggressive, and will tirelessly defend a territory around their nesting site from other males. Due to the extent of territory required to support a population, specificity of nesting conditions, and habitat loss, there are just two known populations of these vireos in the state of Oklahoma.
In 2018, Black-Capped Vireos were delisted as a federally endangered species, and since then Jeremy and his team have been keeping an eye on both Oklahoma populations to ensure they remain stable. A key objective in recent years is monitoring recovery and distribution of the vireo's territories after a wildfire burned through much of one of the Oklahoma nesting locations in 2022. In the first years after the fire, these highly territorial birds were nesting closer than usual in marginal habitat. However, it appears that as new growth matures, the vireos are moving back into the burned areas.
Long-term monitoring efforts like these help us better understand how species respond to environmental disturbance and give us a more nuanced understanding of what Oklahoma's wildlife needs to thrive.
