I got my degree in wildlife and fisheries management and the one thing that the professors constantly stressed when referring to "habitat" was the importance of food. In reality you could probably use the terms "habitat" and "food" interchangeably. Mammals, birds, fish, and pretty much everything make food their #1 priority. Sure they need shelter and reproduction as well, but they look for those in place near available food. The only exceptions I can come up with are maybe a buck during the rut or a salmon in freshwater, they forget about food temporarily