Avian Conservation and Ecology (Dec 2021)
Rat snakes, cowbirds, and vines lower passerine nest survival in remnant bottomland hardwood forests in east-central Arkansas, USA
Abstract
Predation is often the leading cause of nest failure among passerines; however, specific causes are often unknown or can be misidentified in the field. Therefore, it is critical to improve our understanding of causes of nest predation and factors that influence passerine nest success. In the remnant bottomland hardwood forests of east-central Arkansas, we monitored 282 passerine nests during summers 2010-2012, including 81 nests at which we deployed video cameras. We calculated daily survival rates (DSRs) across species, locations, and years and determined which temporal, biological, and habitat variables correlated with nest success. We also estimated predation rates by specific predator groups. Our largest sample-sized species, Indigo Buntings (Passerina cyanea, n = 143 nests) and Northern Cardinals (Cardinalis cardinalis, n = 97 nests), had similar mean DSRs (0.932 ± 0.01, 0.924 ± 0.01, respectively). Predation by all species and parasitism by Brown-headed Cowbirds (Molothrus ater) together were the most frequent causes of nest failures (29% and 33%, respectively), although black rat snake (Pantherophis obsoletus) was the most frequent predator (37% of known predation events). Nest stage and number of vine tents best explained variation in DSRs; however, predictors of predation rates varied across predator groups. For example, vegetation density negatively influenced the probability of nest predation by snakes and mammals, but positively influenced the probability of nest predation by cowbirds and did not influence the probability of nest predation by other avian predators. Using camera systems can help elucidate nest fate patterns and predation trends across species and highlight factors such as time of predation, accurate nestling age, and interspecific interactions. Importantly, our predator-specific results suggest managers should consider techniques suitable for the suite of passerines and predators in their local ecosystems to alleviate high predation pressure, facilitate successful reproduction, and ultimately, population persistence.
