Wild birds need the best possible territory for feeding, mating and raising young, and they claim that territory in a variety of ways. This type of bird behavior can be valuable for birders to understand, because knowing how birds claim territory will help birders understand the great lengths birds go to in order to raise their families.
Birds choose a territory because it can meet their needs for food, water, shelter and nesting sites. The size of the territory will vary by species. Some bird species need large territories with little competition, while other birds have much more communal needs and are more apt to share territory with larger flocks. The size of a bird's territory can also vary from year to year depending on how viable and productive the land is. In a year when there are excellent food sources, for example, a bird may claim less territory than in years when food is scarce.
The amount of aggression birds show defending their territory also varies based on the species and their interaction with one another. An American robin, for example, will chase away other robins from its territory, but it won't mind a white-breasted nuthatch sharing the same space because the two species do not compete for food sources.
How Birds Claim Territory
Migratory birds may begin to claim territory in late winter or early spring as mature males arrive from their wintering grounds and seek to find the best places where they hope to attract a mate. Non-migratory birds will also renew their claims on territory at this time, in part to attract their own mates and renew bonds but also to let arriving migrants know that the territory is already spoken for.
Birds claim territory through a number of behaviors, including:
- Singing: Singing is one of the most common ways birds advertise that a territory belongs to them. Songs will carry quite far, and birds will perch near the edge of their territory to broadcast their claim to the maximum range. At the same time, a strong, vibrant song will help attract a mate. For some species, such as the northern mockingbird, a more complex song will help birds defend a larger territory and is more attractive to females.
- Nest Building: Some birds, such as different types of wrens, will claim territory by taking advantage of the nesting sites it offers. The males will build multiple nests in suitable locations throughout their territory. The females will then investigate those nests and choose the one they prefer, even if they eventually rebuild the male's construction to suit their preferences.
- Drumming: Woodpeckers and several types of game birds claim territory by drumming as an alternative to singing. These low-pitched, rhythmic sounds – whether made by pounding on a hollow tree or by using air sacs – will carry great distances. This alerts competing birds that the territory is not available, as well as lets potential mates know that a strong, healthy bird has claimed the location.
- Visual Displays: Visual displays such as puffing up colored feather patches, tail flicking or fanning, wing spreading and other behaviors are all part of claiming territory. These postures and actions also show off a bird's strength and health to a potential mate. These behaviors are commonly a part of courtship rituals between opposite sexes as well as territorial displays between two male birds.
- Chasing: As a last resort, aggressive birds may directly chase intruders or competitors out of their territory. This is frequent in areas where many birds are seeking to claim the same space, or when a dominant male is discouraging younger males that are struggling to claim their first territory. In bird species where family groups remain together in the winter, the male parent may chase away his mature offspring the following spring so they do not infringe on his territory.
Most birds will use a combination of different behaviors to claim and defend territories, particularly in competitive seasons. Understanding this type of behavior can help birders better appreciate the birds they see and learn more about how birds strive to survive.
When Territory Doesn't Matter
There are two instances when territory is less important to birds. The first is when a bird species is not territorial at all, such as with communal nesting birds. Swifts, swallows, herons and many waterfowl are communal nesters and will have only very small territories directly around the nest site that they may defend.
Birds are also much less territorial after the breeding season ends. At this time, many birds that would have aggressively defended their space just a few weeks earlier are now gathering together for migration and are less apt to be aggressive. Even non-migratory birds are less aggressive at this time, since competition is easing for food sources and they no longer have the demands of growing chicks to meet.
Understanding bird territories and how they claim those territories helps birders better appreciate birds in the spring and summer, and territorial behaviors are always astonishing to observe.