Golden-cheeked Warbler Population Viability and Habitat Suitability Within the Balcones Canyonlands Preserve

Golden-cheeked Warbler Monitoring Our permit requires that we protect habitat and conduct long-term monitoring to assess population viability. Photo by John Ingram Photo by Gil Eckrich

5-Year Study (2011-2015) Conducted under contract with the U.S. Forest Service/Univ. of Missouri and with BCP partners and many volunteers. 4 key questions: How many Golden-cheeked Warblers are there on the Balcones Canyonlands Preserve and within individual macrosites? How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? How viable are these populations? How do various management scenarios influence viability? Photo by John Ingram

Methods: Intensive Territory Monitoring Modeled after Fort Hood’s monitoring program Color-banding Average >70% adult males banded per plot Intensive territory mapping March 15-May 25, 10-20+ visits Typically 2 people per plot Average >130 hours/100 acres Nest monitoring, productivity March 15-June 15

Photos by volunteer Nancy Norman Resighting Photos by volunteer Nancy Norman We enlisted an enthusiastic corps of ~40 volunteers each year to search for banded GCWAs in areas outside the intensive monitoring plots.

Point Count Surveys 5-minute surveys on a grid of points with 250-m spacing across the Balcones Canyonlands Preserve Designed to allow rapid assessment of large areas Study design includes comparisons with intensive study plots 1,507 points surveyed from 2011-2014

Vegetation Measurements Point Count Stations and Nests 5 m radius 11.3 m radius Canopy cover Ground cover Shrub Grass/forb Bare (ground, rock, debris) Litter Small stem density Ashe juniper Live oak Other oak/hardwood Other deciduous shrub Other exotic Avg juniper height Avg non-juniper height Tree DBH Ashe juniper Live oak Red oak Shin oak Cedar elm Other Slope & aspect

Study Results Predicted Density of male GCWAs Question 1: How many Golden-cheeked Warblers are there on the Balcones Canyonlands Preserve and within individual macrosites? Answer: Current estimate is ~2,000 male Golden-cheeked Warblers, with highest densities in the Bull Creek and Cypress Creek macrosites.

Caution: GCWAs immigrating from other areas due to habitat loss can “mask” population declines – which emphasizes the importance of documenting return rates

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: Large tracts of closed-canopy forests of Ashe juniper and oak are critical for GCWA conservation.

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: More large Ashe juniper trees support higher GCWA densities. Photo by John Ingram

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: GCWA density increases with increasing canopy height.

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: GCWA nest survival tends to be highest in Ashe juniper trees. Photo by Gil Eckrich

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: Nest survival increases with higher densities of Ashe juniper trees.

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: Nest survival is highest on uplands and decreases on steep slopes.

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: Understory is important for nest survival (and for fledglings!).

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: Nest survival tends to vary within and among years.

Estimated dispersal distances of males (2011-2015) Study Results Question 3: How viable are these populations? Answer: The USFS/Univ. of Missouri are currently running the PVA models. However, we do know that adult and juvenile survival, productivity, and dispersal are all critical and need to be as high as possible to ensure long-term population viability. Estimated dispersal distances of males (2011-2015) Over 90% of the banded GCWA males returning from their wintering grounds are observed on or near the same territory as the previous year.

Study Results Question 4: How do various management scenarios influence viability? Answer: Need to provide large forested tracts of Ashe juniper and oaks with minimal edge, and manage for mature forest with closed canopy and diverse understory. Photo by Gil Eckrich

References Reidy, J.L., F.R. Thompson, C. Amundson, and L. O’Donnell. 2016. Landscape and local effects on occupancy and densities of an endangered wood-warbler in an urbanizing landscape. Landscape Ecology (DOI 10.1007/s10980-015-0250-0). Reidy, J.L., F.R. Thompson, and L. O’Donnell. In review. Density and nest survival of golden-cheeked warblers varies with plot, forest, and landscape characteristics. Working on two more manuscripts: GCWA adult/juvenile survival Population viability analyses

Acknowledgments U.S. Forest Service University of Missouri City of Austin Travis County LCRA Travis Audubon Society The Nature Conservancy Many volunteers!! Photo by Volunteer Misa Soliz

Any Questions? Golden-cheeked warbler fledglings taking a bath Photo by: John Ingram

Study Results Question 2: How do demographics (e.g., density, productivity, survival) vary with landscape and habitat factors? Answer: GCWA density declines with increasing urbanization.