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Wednesday, October 2, 2013

The only two reasons why birds sing

Harris' Sparrow
The only two reasons a bird sings are (1) defining and protecting its territory, and (2) attracting a mate.  It’s not meant to disturb your sleep or to complain that a feeder’s empty, though those may be secondary consequences. A singing bird doesn’t really care how a song affects us. He just cares if his message gets through to other birds.

Singing is almost always directed at members of the bird’s own species. Each species has a different song (or songs), and individual birds of the same species sound pretty much alike. However, there is often a slight variation among different populations of the same species; for instance a wren in New England probably sounds strange to a wren from Louisiana. Also, almost all birds have two “voice boxes”, so they can sing intricate and complex songs that you and I can’t possibly imitate.

Typically only the male bird sings, although the female of some species can also sing. The reason is common sense; the males want to draw attention to themselves, whereas females want to remain hidden, since they are often in the vulnerable position of incubating eggs or caring for young.

Most bird songs establish territory. Within this territory a pair of birds will get the bulk of their food, hunt for nest material, raise their young, and so on - so a territory must be aggressively guarded from rivals. The relative size of a territory varies greatly. It depends on the amount of food, shelter and nesting material it contains.

To establish a territory, the male chooses a series of song posts from which to sing (specific trees, fence posts and such).  The borders are invisible, of course, but if a rival male crosses into an occupied territory he will be instantly challenged. When a male challenges, the ensuing fights or chases may involve aggressive bursts of song meant to scare the intruder. The territory’s original “owner” almost always emerges as the winner.

Special attractions that appeal to all birds, like feeders and birdbaths, seem to be excluded from the exclusive territory of just one bird. They’re out-of-bounds or “neutral territory” which all birds can visit with only minimal annoyances from other birds.

A bird’s song means nothing to birds of a different species. The other bird probably has different food and nesting requirements, so different species often live in the same area, ignoring the songs of other species. Within a given territory it’s possible to have a Robin, a Cardinal, a Chickadee, a Mockingbird and Bluebird, all nesting without interfering with each other’s needs. One species eats seeds, another eats insects and so on…each exploiting its own environmental niche. An example is the Brown Creeper, who inspects tree bark for insects while going UP a tree. The Nuthatch does it while going DOWN a tree. So they can both live on the same tree, and not infringe on the other’s environmental niche.

A bird’s song can advertise to a female that an unattached male is present, offering the female a mate and a home. He’s announcing his status and virility (some call this the “shiny sports car” syndrome).  The female is thought to be able to distinguish between the songs of a bachelor bird and one that is paired. 

Some birds also have a sub-song.  It’s usually a quieter and lower version of their normal song. It doesn’t carry very far and is usually only heard in fall and spring. Some sub-songs are almost certainly sung by young birds, so it could be thought of as  ”practicing”.

Bird calls are different from songs. They are quite short, simple sounds and so have only one or two syllables; sort of like a sound you or I might make if startled, punched in the stomach or attacked by a bear. Calls communicate totally different messages from songs – such as signaling that a predator is very near, showing aggression, showing surprise or calling young birds home.

Whatever song a bird makes, it typically sounds pleasant and sweet to us. But to the intended audience, other birds, it may mean ”get out of MY territory” or “I can help raise healthy nestlings” or “watch out for that hawk up there”.


OWEN YOST, in addition to being a blogger, is a licensed Landscape Architect emeritus who has lived and worked in north Texas for over 30 years. He is a member of the American Society of Landscape Architects (ASLA), International Federation of Landscape Architects, National Wildlife Federation and the Audubon Society. His office is at in Denton.


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