LeConte’s thrasher monitoring at Tule Springs Fossil Beds National Monument: A three-year report (2022–2024)

Simmons, John

doi:10.36967/2306923

LeConte’s and Bendire’s Thrashers (LCTH and BETH, respectively) are recognized as some of the most rapidly declining bird species in the American southwest. Tule Springs Fossil Beds National Monument (TUSK) contains a mosaic of different habitats favored by LeConte’s Thrashers (LCTH). At the same time, Bendire’s Thrasher has never been recorded on TUSK. These habitats exist in a spectrum of disturbance regimes, from pristine habitats (found in the northeastern parts of the park) to more disturbed habitats (found along the entire southern border near the urban interface). The precipitous decline of thrashers has called the Desert Thrasher Working Group (DTWG) into action across these species’ ranges to collect distribution data and create habitat suitability models. Area search surveys have been implemented on TUSK for three seasons, beginning in 2022. Following the protocol outlined by the DTWG and Great Basin Bird Observatory (GBBO) (DTWG 2018), 33 plots, sized at 300 × 300 meters, were visited a total of 8 times each. Vegetation data were also collected at each plot using the point-centered quarter method to determine dominant cover species, percentage of bare ground (important for ground-foraging arthropod hunters like LCTH), vegetation height, wash coverage, and presence of invasives. A total of 88 bird species were recorded. Survey data reveals that LCTH, which were detected on 20 out of 33 plots, prefer nesting sites in or near saltbush dominated habitats while occurrence differed across areas experiencing different levels and types of human disturbance. Human disturbance refers to anthropogenic activities and infrastructure that may negatively affect habitat and LCTH. At the same time, distance from human disturbance does not appear to play as significant a role as the type and intensity of disturbance, as thrashers inhabited quality habitat in close proximity to humans while disregarding poor quality habitat at similar distances. Areas with a mosaic of saltbush, soft alkaline soils with a moderate number of rocks, and creosote bush also usually indicated thrasher presence.

LeConte’s thrasher monitoring at Tule Springs Fossil Beds National Monument: A three-year report (2022–2024)

Series