How can one not be outright ecstatic about this special group of birds that comprise about 60 percent of all bird species in the world? They adorn our planet with their sheer numbers, their looks, and their songs; the natural world is so much richer with them as our fellow travelers on this earth.
WITHIN THE PASSERINE GROUP ARE TWO SUBGROUPS, one of which is called the songbirds. Numbering about forty-five hundred species, the songbirds’ Latin name is oscines, literally translated as “birds with voices.” These are the wrens and warblers, thrushes and thrashers, sparrows and tanagers, cardinals, blackbirds, and many more—so many of them terrifically accomplished songsters. They sing because they are designed to do so, with especially complex voice boxes (called syringes) that can deliver intricate sounds precisely. Their specialized brains have vast neuronal networks to control their singing routines; these networks also enable young birds to memorize the intricate details of adults’ songs, beginning at about two weeks of age. By three weeks, just out of the nest, the baby songbird begins to babble just like a human child, and as he babbles away, he listens to himself, trying to match his scratchy, uneven attempts to the song memories he has already stored in his brain. In most species, by the time he is a year old, he will have perfected the songs that he will sing for the rest of his life. Dialects also occur in their songs, just as in our speech. And in the same way that our ability to learn has enabled us to acquire large vocabularies, songbirds can, too, some of them learning the nuances of hundreds or even thousands of different songs.
The songs in most songbirds’ repertoires are multipurpose songs; they’re used both to impress females and defend territories, and no particular song has any special meaning. Singing is more specialized among some warblers, however. For these species, males use one song (or group of songs) largely during the daytime to address females, and another song (or group) when arguing with males, especially during the dawn chorus. To be successful, a male must learn not only the form of the song but also when to use it.
The songbirds appear last in this book, reflecting their relatively recent (in a geological time frame) success and proliferation. Birds of the other passerine subgroup—typically called the “sub-oscines”—are equally fascinating. The roughly eleven hundred sub-oscine species occur mostly in the tropics of Central and South America; just a small handful of flycatchers have made it to North America. In general, sub-oscine voice boxes are simpler and their brains lack the special wiring for song learning that is found among the songbirds. Because their songs are inborn, they tend to be relatively simple and the repertoires relatively small. The accounts for five of these flycatcher species are next; following the flycatchers are the accounts for the fifty-four songbirds.