The impact of natural selection on the feeding preference of birds in northern Michigan.

Abstract

Natural selection may influence feeding preference by selecting for levels of nutrients that may be beneficial to survival and reproduction. We hypothesized that this force may be acting on bird feeding preference by associating taste with high levels of nutrients. We observed bird feeding preference in northern Michigan and compared it to the nutritional content (protein, lipids, carbohydrates, and calories) of ten food sources. We found a difference in feeding preferences of the male and female Red-breasted Grosbeak (Pheucticus ludovicianus) (X2 = 57.9777, d.f. = 4, p<0.001), possibly due to the demanding reproductive costs of the female. We also found a difference in the feeding preference of small birds and large birds; smaller birds preferred foods with intermediate carbohydrate levels and high lipid levels, whereas, larger birds preferred foods high in carbohydrates and low in lipids. Overall, we found no evidence that birds in general chose foods based on nutritional content.