Figure 1. SongMeter SM4 units were installed along a transect running perpendicular to Capital of Texas Hwy within the riparian corridor of Bee Creek.

Dr. Amy Belaire
St. Edward's University, Wild Basin Creative Research Center, Austin, TX

Background

Wild Basin Wilderness Preserve is a 227-acre protected natural area located just 10 minutes from downtown Austin, Texas. With 3 miles of public hiking trails, it serves as a rare and accessible green space in an increasingly urbanized environment. In spring 2017, a biodiversity monitoring project was launched at the preserve, with a particular focus on avian species during their breeding season. The study was conducted by three St. Edward’s University student interns—Gabby Macias, Olivia Leos, and Anne-Marie Walker—under the mentorship of Dr. Amy Belaire.

The primary goals of the project were to:

  • Monitor the impact of urbanization on bird and amphibian populations.

  • Detect and map the presence of the endangered golden-cheeked warbler (Setophaga chrysoparia).

  • Test and refine acoustic monitoring techniques in a real-world field setting.

Study Design and Methodology

To achieve its objectives, the team deployed Wildlife Acoustics SM4 Song Meter recorders using a transect approach:

  • Transect Design: A straight-line transect was established perpendicular to Highway 360, extending deeper into the preserve along Bee Creek, a riparian corridor. This design was chosen to examine how anthropogenic (human-generated) noise from the highway influences wildlife presence and behavior.

  • Acoustic Units: Three SM4 units were spaced ~300 meters apart along the transect. A fourth unit was rotated among various locations, targeting areas likely to be inhabited by the golden-cheeked warbler.

  • Recording Schedule: Each unit was programmed to record one hour post-sunrise (to detect birds) and one hour at night (to detect amphibians such as frogs and toads).

  • Calibration: Before deployment, all recorders were calibrated using pink noise in the University of Texas's anechoic chamber. This ensured consistent data quality across all units.

  • Anthropogenic Noise Measurement: An iPad with an external microphone was used to measure noise levels along the transect, capturing baseline data on urban soundscapes.

Field Implementation and Observations

The project combined hands-on fieldwork, data analysis, and skill development in acoustic ecology:

  • Testing and Training: Interns field-tested the units by playing recorded cardinal calls at different distances and analyzing spectrograms using Kaleidoscope software. This software grouped similar calls into clusters to facilitate identification.

  • Songbird Identification: Students trained using online tools like the Cornell Lab’s Bird Song Hero and mobile bird ID apps to recognize and categorize calls by ear—skills they later used to verify software-generated clusters.

  • Urbanization Gradient: By placing recorders from a high-traffic area near the highway to quieter interior habitats, the team began identifying shifts in bird presence and behavior along the urbanization gradient.

Key Findings and Insights

  • Successful Detection of Golden-Cheeked Warblers: The rotating fourth unit proved effective in detecting the elusive and endangered golden-cheeked warbler, confirming that the species continues to breed within Wild Basin.

  • Multiple Species Detected: The SM4 units detected a wide variety of songbirds including Northern Cardinals, Carolina Wrens, Blue Jays, and others. Kaleidoscope software enabled sorting and long-term tracking of individual species’ presence.

  • Noise Influence Observed: Preliminary analysis suggested that species richness and vocal activity decreased near the highway, highlighting the potential impacts of urban noise pollution on wildlife.

  • Enhanced Awareness and Education: Interns reported a dramatic increase in awareness of bird sounds in their daily lives, turning background noise into a meaningful aspect of the natural world.

Conclusions

This project demonstrated the effectiveness of acoustic monitoring in assessing biodiversity in urban-proximate natural areas. It also served as a powerful learning opportunity for undergraduate researchers, providing hands-on experience with fieldwork, calibration, spectrogram analysis, and bioacoustic interpretation.

Notable takeaways:

  • Passive acoustic monitoring is a low-impact, scalable method for tracking wildlife in sensitive habitats.

  • Student involvement in citizen science contributes meaningfully to both conservation and education.

  • The transect design offers valuable data on how urban pressures influence species distribution over short spatial gradients.

  • Data collected has laid the groundwork for long-term monitoring of avian and amphibian communities in Wild Basin and other urban preserves.

Future Directions

  • Expansion of monitoring to include seasonal variations and additional taxa (e.g., bats, insects).

  • Development of a long-term acoustic database for trend analysis.

  • Public engagement initiatives using citizen science apps and acoustic stations to connect urban communities with local biodiversity.