Reproductive Success of a Rapidly Declining Blackbird (Quiscalus quiscula) in Central Illinois

The common grackle (Quiscalus quiscula) was once one of the most abundant bird species in the Midwest. As recently as 1960, the global population was estimated at almost 200 million individuals (Sauer et al. 2017). However, steady declines over the past 40 years have reduced their population by 58%, to roughly 73 million. This makes the common grackle one of the most rapidly declining common birds in North America (NABCI 2014). Interestingly, this decline has intensified in the eastern tallgrass prairie region since the turn of the century. Around the same time, U.S. agriculture began the mainstream adoption of neonicotinoid seed treatments (NSTs). Neonicotinoids, a class of neuro-active insecticides, are currently applied to 94-98% of corn seed and 34-44% of soybean seed in the U.S. and are linked to avian declines across Europe and North America (Hallmann et al. 2014, Stanton & Clark 2018). The exact mechanism of neonicotinoid exposure and action in birds is complicated, poorly understood, and expensive to test, so my work aims to take preliminary steps towards causation by first examining the reproductive success of a declining species with high predicted exposure to neonicotinoids: the Common Grackle. Over two years, I have monitored 196 nests across two sites in Champaign County, IL. From these nests, I have banded and tracked the activity and survival of 56 fledglings using hand-held and automated telemetry. I estimated nest success at 0.572 (SE = 0.002) and 20-day post-fledging survival at 0.662 (SE = 0.006). Moving forward, I will be expanding upon this analysis to investigate post-fledging activity, habitat use, and movement, as well as constructing a population viability analysis using my values for reproductive success and established adult survival values from the literature. My work on common grackle reproductive success may inform and direct future studies in their investigation of neonicotinoid insecticides, as well as other mechanisms of decline affecting common birds across North America.