Why do birds sing? To warn and woo

In 1956 Frankie Lymon and the Teenagers took "Why Do Fools Fall in Love?" to No. 6 on the U.S. popular music charts. In 1981 Diana Ross took the same tune to No. 7. I can't imagine there's anyone unfamiliar with this popular song, and I suspect it's at least partly responsible for the widespread misunderstanding of the meaning of bird song.
No, I haven't lost my mind; there is a strong (though misleading) connection between birds and fools falling in love. The second verse begins by asking, "Why do birds sing so gay?" Is it unreasonable to assume that after hearing this question hundreds, if not thousands of times, hormone-driven teenagers might conclude that birds sing because they're happy? I think not.
But contrary to what may seem intuitively obvious, birds do not sing for joy. They sing for two very specific, serious reasons. But before we get to that, let's examine bird vocalization in general.
Throughout the year birds vocalize to communicate everyday information. Ornithologists label these sounds "calls." They convey information between members of a flock on location, food sources and social position. Calls also communicate alarm, danger, aggression and annoyance. In human terms, calls are the sounds of daily conversation.
Bird song, on the other hand, is typically limited to the breeding season, though there are exceptions. I often hear white-throated sparrows and Carolina wrens sing in January. And songs are usually sung by males, though our understanding of that continues to evolve. Females of many species, including cardinals, sing, though their songs are typically more subtle than males'.
Marking territory
Males sing for two reasons, and the message depends upon who is hearing the song. Male birds establish and defend a territory from other males of the same species by singing from perches around and within the territory. In this sense, song is a keep-out signal. Other males know that if they violate a territory's boundary, they will be attacked. So they respect a territory holder.
Furthermore, a single male can create the illusion that a territory is overrun with competing males, and therefore undesirable, by singing from many perches within the territory.
Mockingbirds, for example, which have an extensive repertoire of songs, sing a different song whenever they move to a new perch. To outsiders, it may sound as if many males occupy the area, so they look for areas where there might be less competition. Thus, the territory holder defends his space by deceiving potential rivals. Why battle many males, the logic goes, when unoccupied and undefended habitat may be over the next hill?
Mockingbirds sometimes take this deception to extremes by singing all night long. If you hear a bird singing between dusk and dawn and it's clearly not an owl or a whippoorwill, it's likely a mockingbird or a yellow-breasted chat. During the nesting season, males of these two species can be heard any time of day or night. It may seem like overkill, but wandering males cannot mistake the keep-out signal.
Attracting mates
On the other hand, male song is also an invitation to females. It says, "I'm available, I've got a nice territory, I can provide for you, let's become a couple." It might be tempting to call it a love song, but biologists prefer to keep emotion out of the equation. It's just part of the pair-bonding process.
Vocalizing may seem a dangerous way to communicate because it calls attention to the singer. Hawks, owls and other predators might use sound to zero in on tasty song birds. But part of the beauty of voice is its brevity. Sound leaves no evidence behind. Once uttered, songs and calls vanish into thin air, so predators can't use sound to locate vocalizing birds. And if danger threatens, birds simply stop talking until the threat passes.
So as you enjoy the spring chorus with your morning coffee, resist the reasonable urge to assume that birds sing because they're happy or because they're in love. Frankie Lymon's lyrics notwithstanding, birds sing to communicate, to defend space, and to attract mates. And on the wild side, it doesn't get more serious than that.
Send questions and comments to Dr. Scott Shalaway, R.D. 5, Cameron, WV 26033 or via e-mail to sshalaway@aol.com.