Spring is a season full of bird song. Just before sunrise each morning, the air is usually filled with the sounds of birds. Birds often sing almost all day long in spring. What have they got to sing about? What are they doing? Let's see what we can learn about bird song.
In New York State, spring is when most migratory birds are nesting. They have spent the winter somewhere farther south where milder winter weather makes it easier to find food. Now that it is spring, they come back north where there are not as many birds looking for space in which to raise a family.
Most birds defend an area big enough to have enough food for young birds when they hatch. This area is called a territory. Some kinds of birds have a pretty small territory while others might need a much larger area to feed their young. Most birds will only defend their territory against birds that are the same kind that they are. That means that a Northern Flicker
will only chase away other Northern Flickers, a Song Sparrow
will only defend its territory from other Song Sparrows. After all, only another Song Sparrow would be looking for exactly the same kind of food to give to its young. Defending a territory only against other birds that are the same kind saves a bird a lot of time and energy. It would be much harder to defend a territory against every other kind of bird that might wander in. For many kinds of birds, the job of defending a territory is usually done more by the male bird than by the female.
How does a bird defend a territory? Mostly by singing. A bird song tells other birds in the area what kind of bird is singing. In fact, each bird song is unique enough that it tells both the kind of bird and which individual bird is singing. So a Song Sparrow’s song tells other Song Sparrows not only that a Song Sparrow is singing, but also which Song Sparrow is singing. Early in the season, there may be chases and fights as territories are being set up. Before long, each Song Sparrow can recognize all the other male Song Sparrows in the area by their songs. If a song he hears is from a neighbor he knows, singing just outside his territory, the Song Sparrow that lives there doesn’t have to fly over and try to chase it away. So bird songs are a way of making sure that a pair of birds have a large enough area to feed their young without having to waste a lot of time and energy chasing competitors away.
There are still a couple of problems here. If a bird chases away all other birds that are the same kind, how will he get a mate? Any Song Sparrow that comes into a male Song Sparrow's territory would get chased away.
First, the female bird decides if she is interested in a male. His song tells her a lot about him – how healthy he is, how big his territory is, and a little bit about how good he might be at helping bring up a nest of healthy baby birds. This helps her decide if he might be good as a mate. If a female Song Sparrow likes a male’s song, she has to get him to let her stay long enough to get to know her. She does this by acting a lot like a baby bird. She will flutter her wings and cry like she is begging for food. By doing this, she keeps the male bird from chasing her. After a while, he may accept her as his mate and they can start to build a nest.
So a bird’s song both helps him to set up a territory and to attract a mate. Other sounds made by birds help to keep flocks of birds together when it is not the nesting season, to warn other birds that there is danger, or to beg food from a mate or parent. Anything that an animal does that helps it meet one or more of its life needs is called an adaptation. Bird songs, and other sounds made by birds, are very important adaptations that help birds survive.
Below are a few common birds you might listen for around your neighborhood or school this spring*. How many can you hear? How many individuals of each kind do you hear?