BCP biologists briefed the committee on Nov. 14 about multi-year monitoring and 2024–25 results for golden-cheeked warblers and black-capped vireos on the Balcones Canyonlands Preserve.

"We band males and track return rates and nesting outcomes," said Bill Reiner, who described intensive monitoring across 13 study plots and volunteer field support. He reported that in 2024 the city had 141 banded male golden-cheeked warblers and 66 of those returned in 2025, a 47% return rate that is better than the 15-year mean of 43%. Reiner said preliminary nest monitoring found 67 fledged of 120 nests with known outcomes, a preliminary nest success rate of about 56% for warblers.

Reiner said the 2025 breeding season showed more territories (about 150 territories on the plots, ~20 more than the prior year) but that early-season nest failures occurred more often, likely from predators (Texas rat snakes, Woodhouse's scrub jays, fox squirrels) and possibly reduced insect prey during dry conditions. "There were many early nests that failed just before the birds fledged," he said, noting that food scarcity may have increased predator pressure.

For black-capped vireos, city staff banded 15 individuals in 2024 and recorded nine returns in 2025 (a ~60% return rate); preliminary nest monitoring counted 34 nests on city sites with 10 fledged of 31 known outcomes, a preliminary nest success of ~32% that is lower than the prior year.

Reiner described long-term methods—color and U.S. Geological Survey metal bands, volunteer search areas, and intensive five‑year studies used to estimate preserve-wide abundance (previous intensive work estimated roughly 1,700 male territories across the preserve). He and staff emphasized that multi-year monitoring is necessary to detect trends and that factors such as El Niño-driven conditions on wintering grounds have previously driven population dips.

The presentation concluded with discussion of banding methods, dispersal distances (typical males show high site fidelity; rare dispersals up to ~60–80 miles recorded), and continued volunteer support for monitoring and nest surveys.