For instance, courtship and mating involve a complex series of displays and vocalizations, and the result of courtship is frequently the formation of a pair-bond. In some species offspring from previous years assist their parents in rearing younger siblings, seemingly models of altruistic cooperation. Birds feed on a wide variety of animal and plant material, and all have specialized ways of obtaining food. Most species migrate to some extent, even if it is only from areas of little food to richer foraging places. Some migrations are amazing feats of stamina and navigation.
Many species live in flocks, although some are typically solitary.
This variation and complexity of behavior and ecology provides much fodder for field biologists. Studies of bird biology have resulted in many general evolutionary, ecological, and behavioral principles. These studies of learning were extended to the natural setting with Lorenz's studies of imprinting, and with later studies of learning of song in many species of birds. Recent studies have shown that many bird species are capable of long-term spatial memory, for instance species that cache food for use during the winter, most notably jays and their relatives. The methods by which birds obtain food are as diverse as the types of food they prefer.