Demographic Response of Breeding Grassland Birds to Keystone Effects of Black-tailed Prairie Dogs

Background/Question/Methods

: Grassland birds are the most steeply declining group of birds in North America, but we lack demographic data needed to improve conservation efforts. Black-tailed Prairie Dogs (Cynomys ludovicianus) are a keystone species that structure bird communities on the Great Plains by generating heterogeneity through ecological disturbance, specifically, grazing and burrowing within colonial “towns.” However, prairie dog effects on nest demography have only been assessed with artificial nests, which suggested higher predation rates on prairie dog towns. To better inform Great Plains community ecology and inform conservation management, we are actively researching the keystone effects of prairie dogs on Horned Larks (Eremophila alpestris) and Chestnut-collared Longspurs (Calcarius ornatus). Working on public land in central MT, we used quasi-random selection to establish 1100 x 300 m transects that span a gradient of prairie dog disturbance, from active colonies (treatment) to surrounding grassland (control), where the transect midpoints fall on colony borders. Within transects, we systematically searched for nests of both species and monitored demographic parameters every 2-3 days. We also collected data on arthropod communities, vegetation characteristics, and prairie dog abundance for future analyses. Here we report preliminary demographic patterns in relation to prairie dogs from our 2021 pilot season.

Results/Conclusions

: We found no difference in clutch size on and off prairie dog towns for either species, nor was there a difference in nest success on and off prairie dog towns for either species. We did not expect to find Chestnut-collared Longspurs nesting on prairie dog towns, and visual assessment of nest sites in relation to prairie dog town edges suggests that nests for both species are distributed closer to prairie dog town edges. Despite a limited sample size of preliminary results, our results indicate that 1) prairie dogs may have neutral effects on predation risk and nest success both species, and also 2) nests for both species appear to be distributed closer to prairie dog town edges than expected. These findings run counter to knowledge from artificial nests. Forthcoming research will explore these patterns in greater precision, test the mechanisms responsible, and provide practitioners with data to better integrate the effects of prairie dogs into bird conservation planning.