BRC-BIO: Looking beyond the calorie: Nutritional ecology in a generalist predator

Calories are often treated as the primary unit of nutrition, but a growing body of evidence suggests that the specific nutrient composition of food may be a more important driver of foraging behavior in wildlife. Because nutrient composition varies with environmental conditions, climate change is likely to affect nutrient content of food. For predators, this means that a changing climate could alter the nutrition of their prey, and therefore, what prey they select. However, without baseline knowledge of how nutrients shift in response to changing environmental conditions, it is difficult to make predictions about predator behavior. Songbirds are common predators in many ecosystems that prey on a variety of insects and can easily be captured and observed for behavioral studies. This project will 1) assess macronutrients (protein, carbohydrate, lipid) in prey and identify specific ratios of macronutrients that maximize nestling growth, 2) examine how the nutritional value of prey changes when reared in experimentally manipulated environmental conditions, and 3) examine whether changes in nutrition affect birds’ preference for prey. Because insects are consumed by many animals outside of birds, this work will have conservation implications for a wide range of taxa. The research team will include undergraduate students enrolled in relevant biology courses and paid undergraduate assistants. Students will develop independent projects related to the broader theme and travel to national conferences to present their work. This research experience will equip participants with skills in laboratory and field work and build students’ confidence to persist in STEM careers. Using a combination of manipulative laboratory experiments and an existing network of 100 Eastern bluebird nest-boxes, the researchers will examine how environmental conditions affect prey nutrient composition and whether these changes impact predator preference. This work will test the use of the nutritional geometric framework: a tool for assessing nutrition by utilizing ratios of nutrients to model how foods are combined to reach multidimensional nutritional targets that maximize organism performance. This framework is useful in modeling how diet changes as different food items change in availability or quality. By measuring the impact of prey macronutrients on nestling development in Objective 1, the researchers will identify multidimensional nutritional targets that maximize growth in nestlings. In Objective 2, these data will be used to test whether the environmental conditions of prey meaningfully impact their nutrient content. Although some studies investigate how nutrients change in response to temperature or diet shifts, very few examine these in combination, even though climate change is predicted to simultaneously affect both. Experiments in Objective 2 manipulating diet and rearing temperature will advance our understanding of how multiple environmental changes interact to determine nutritional value. Finally in Objective 3, researchers will examine bluebird nutritional preferences using field-based choice assays with nutritionally altered insect prey. The experiments in this project will advance basic science of nutritional ecology by examining hypotheses from the nutritional geometric framework and life history theory, the outcomes of which will inform conservation applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.