Tree Swallows. Photo: Jerry Amende/Audubon Photography Awards Most kinds of birds defend territories during the breeding season, driving away other birds of their own kind. Tree Swallows don’t defend large feeding territories, since they range widely in pursuit of flying insects, but they can be very aggressive in defense of their nest site. Early in the season, when the swallows are choosing nest cavities, they often engage in spectacular aerial skirmishes over choice sites.
