Assistant Professor Texas A&M University, United States
Background/Question/Methods:
The years following an acute disturbance event provide a valuable opportunity to understand the dynamics of avian communities. In this study we investigate the avian community dynamics at the Welder Wildlife Refuge in central, coastal Texas in the three years following the local impact of Hurricane Harvey in August 2017. We implemented an array of 45 avian point counts in addition to 18 autonomous recording units to monitor breeding bird activity in 2018, 2019, and 2020. Each point was sampled three times during each breeding season, with an unlimited distance-based survey protocol. Autonomous recording units were deployed along a wetland gradient and set to record daily from May-July of each year for a one-hour period immediately post-sunrise. We conducted diversity analysis within, and across, all points each year and calculated occupancy rates for the most frequently detected species. In addition, we conducted annual 100ft linear vegetation surveys at each avian point count location. We then built a series of linear mixed models to disentangle the impacts of vegetative cover and vegetative species composition on avian occupancy and diversity in this coastal mesquite-huisache ecosystem, and how those impacts have changed within this three-year period.
Results/Conclusions:
A total of 71 species were detected through avian point count sampling across all years and all point visits. The three most commonly detected species, across all distance bands, were northern cardinal (Cardinalis cardinalis; n = 1264), painted bunting (Passerina ciris; n = 1164), and white-eyed vireo (Vireo griseus; n = 774). After adjusting for “flyovers”, or species that were detected while not actively utilizing the habitat present at a given point, a total of 12 species exceeded 75 total detections across all point visits and years. Notably, three species with total detections < 75 experienced large differences in detections between years: greater roadrunner (Geococcyx californianus; 42 in 2018 and 2 in 2019), brown-crested flycatcher (Myiarchus tyrannulus, 30 in 2019 and 7 in 2020), and dickcissel (Spiza americana, 24 in 2019 and 0 in 2020). Preliminary results suggest that groundcover density, overstory density, and overstory diversity exhibit a positive relationship to avian diversity within a 125m radius, while their relationship with occupancy rates of frequently detected species is species-specific and differs little between years, as expected. Results of this study provide additional insights regarding the community structure, temporal dynamics, and habitat relationships of an avian community in coastal Texas.
