By Thomas Milligan, U.S. Army Environmental Command
JBSA FORT SAM HOUSTON, Texas — The story of the black-capped vireo’s rebound from an endangered species is a true success story – the songbird was listed as an endangered species in November 1987, but due in part to Fort Cavazos’ conservation efforts, the black-capped vireo was delisted in 2018.
The Natural Resources Management Branch staff at Fort Cavazos will tell you, however, that this work doesn’t end with a delisting of a species but continues on, not just for one bird population but for the many different animal and plant species and land that they help to preserve and protect.
In addition to ongoing work to collect data and continue to protect the vireo population, the team is fully engaged in efforts to protect and preserve the golden-cheeked warbler – another small, songbird species facing population challenges.
Fort Cavazos’ research and conservation efforts of the endangered golden-cheeked warbler have included nest survival rates, forest cover and its impacts on density, and nest predation. Since 2003, the team has monitored 1,252 warbler nests and since 1999, they have banded approximately 5,000 warblers. Since 2016, this team has conducted more than 1,000 point transects per year, and have recently collaborated with numerous entities on research projects, to include breeding range wide population survey, radio telemetry study on fledglings, source sink population dynamics, meta barcoding analysis on prey consumption, several modeling efforts and is currently finishing up on a five year study that examined the migratory connectivity for this species, their migratory paths and overwintering locations by using tracking devices. The study is part of a larger study that is conducting a threat assessment on both the wintering and breeding grounds.
“Protecting the environment and supporting the installation and its mission requires painstaking work, and a passion to serve amongst all the land management stakeholders,” said Tim Buchanan, Natural and Cultural Branch chief. “Our team has been successful because of their dedication, skill and expertise. We’re proud of the past accomplishments, and excited to meet the challenges ahead.”
Appropriate stewardship and management practices aren’t confined solely to preservation, but also require population control of invasive or damaging species. For example, brown-headed cowbirds will destroy the eggs of vireos and other songbird species. The team set a goal of reducing parasitism by cowbirds of vireo nests below 10% over a five-year average in managed study sites. To address post-delisting recovery, Fort Cavazos is continuing a 12-year scientific experiment to determine the impact should trapping and shooting activities stop.
One very notable feature of Fort Cavazos’ landscape is the presence of karst features — a limestone landscape that contains sinkholes, caves, rock shelters and springs.
These karst features are ecologically sensitive, often providing very specific habitat and microclimate for karst fauna, including bats (one species soon to be endangered), salamanders and 16 endemic cave adapted invertebrate species. From the 1990s to the present, karst ridge walks, exploration, mapping, inventory, biological surveys and studies have resulted in the discovery of many karst features. At present, 360 caves, 1,035 sinkholes, 320 springs and 890 rock shelters are documented on Fort Cavazos.
Monarch butterfly population
In the last decade, the dramatic decline in the Monarch butterfly population has drawn attention from agencies and environmental organizations around the globe. Because Fort Cavazos is on the Texas central flyway of Monarchs as they return to their wintering grounds, the natural resources team has joined in on data-collection efforts to help preserve the threatened species.
In 2017, Fort Cavazos began a Monarch tagging program. To date, 9,807 Monarchs have been captured, tagged and released. Adhesive tags were provided by Monarch Watch, a nonprofit education, conservation and research program that is based at the University of Kansas and focuses on the Monarch butterfly, its habitat and fall migration. The butterflies are measured for body condition, wing length, weight, sex and nectar source use. Comparing this data over the course of several years will provide valuable insight into species trends.
“Applying insights from this high-quality scientific data to the development of land management practices in collaboration with the Range Operations training area management team has resulted in successfully supporting both the conservation and military training missions,” Buchanan said.