Date of this Version
Environmental Studies Undergraduate Student Thesis, University of Nebraska-Lincoln, 2021.
Wintering birds are particularly susceptible to predation while foraging at feeders. The ‘starvation vs. predation’ survival trade-off is felt most acutely in winter because energy demands are higher compared to milder seasons. This study investigated sense of predation risk experienced by members of a wintering mixed-species flock. The objective was to determine which species take on increased predation risk in order to forage at feeders, and if there was bias for one species over another. A raptor (experimental) and non-raptor (control) model were presented to a mixed-flock at feeders within Pioneers Park Nature Center. The first species to return to a feeder after a presentation and the time for that species to return were recorded. Out of 43 trials, the top three returning species were Black Capped Chickadees (32.1%), Downy Woodpeckers (28.6%), and White Breasted Nuthatches (21.4%). The other winners were Red Bellied Woodpeckers (14.3%) and a Goldfinch (3.6%). Among the top three, no significant bias for one species over another to return first was found (p-value > .05). The number of flight responses and return times were significant at p < .05, suggesting the flock perceived the experimental model to be a greater risk than the control. These results are intriguing because BCC are known as mixed-flock leaders whose alarm calls are closely followed by satellite species like NH and DWP. But the statistical results of this study do not provide direct evidence of this. Any large-scale negative impacts of supplementary feeding on avian ecology, like the effect of predation on mortality rates, are not well understood. Further research is recommended in order to understand the implications of supplementary feeding on conservation.