Nutritive value of two important prey species 

Sebastian worked with us through the Raptor Research REU Program at Boise State University and aimed to understand the nutritive value of two important prey items for Gyrfalcons. This is an important piece of information because not all food is equivalent. Eating 5 g. of chicken isn’t the same as five grams of Twinkies, but most diet studies only consider the living biomass of prey species. So since Arctic ground squirrels and ptarmigan are of similar size – they are considered similar value in the models describing diet. But we wanted to dive deeper and understand the true nutritive value of these species. He found that in fact the living body mass was similar between squirrels and ptarmigan but that the Edible biomass ptarmigan was double compared to squirrels – due to the squirrel’s heavier skeleton, guts, and hide that the gyrfalcons do not eat. Ptarmigan also contained higher amounts of protein and similar levels of energy and fat compared to squirrels suggesting that overall Ptarmigan provide more meat per prey item and are more nutritious than squirrels. Sebastian learned a lot about raptor handling, sample collection, and rappelling and he is now planning on becoming a raptor biologist, which I am sure he will be great at.