Listen to the fluted chorus of a Wood Thrush, a beautiful song known to inspire artists and enliven eastern forests each summer. Now hear the gruff squawk of an American Crow.
Which is the songbird? If you said both, take a bow.听
鈥淪omething can be a songbird and not be an impressive singer,鈥 says 探花精选 field editor Kenn Kaufman. So, if singing ability doesn鈥檛 make a songbird a songbird, then what does?听That question is actually a lot trickier to answer than it might seem.听
The general public might throw the term around loosely, but for scientists, 鈥渟ongbird鈥澨齢as a more detailed meaning: It refers to a specific suborder of birds.听All songbirds are perching birds, an order called passerines that share a distinct toe arrangement that helps them grasp branches. Passerines are separated into three suborders, the largest of which is Passeri. Birds in the Passeri suborder are called oscines, or songbirds. The suborder includes more than 4,000 species that range听from the compact Golden-crowned Kinglet to the much larger Common Raven.听
Despite their variety in size and musical talent,听all songbirds do have听something in common: precise control of a highly specialized vocal organ . Almost all birds use a syrinx to produce sound, but oscines have superior mastery of theirs. 鈥淭he big difference is not the syrinx itself, but the muscles around it,鈥 Kaufman says. 鈥淭he oscines have a whole series of really complex muscles attached to the syrinx and it gives them much greater control.鈥澨
When a bird exhales, it can engage muscles inside the syrinx that control a . As air flows over these membranes, they vibrate to create a specific tune. Because songbirds have the most control over their vocal organ, they can produce the most dramatic ballads.
Another trait that sets oscines apart is that, while other perching birds produce their songs from instinct alone, songbirds learn theirs. Research shows that听听but need adult tutors to become expert vocalists. Young songbirds on their parents and other adults as nestlings. Some have a window of just a few months to learn their songs, while others, such as European Starlings, can add to their setlists听through adulthood.听鈥淪ongbirds have taken advantage of this ability to learn songs to produce very complex and large reportoires,"听says Donald Kroodsma,听a retired ornithologist who studies birdsong. Other passerines听only have a handful of tracks at their disposal.听
That said, birds don鈥t always fit into tidy categories; Kroodsma's听听shows that the听鈥攁 Central American passerine belonging to a different suborder鈥攎ight also rely on learning to hone its tune, suggesting song learning exists outside of oscines.
While there is no authoritative听definition of what听constitutes a bird鈥s song versus its听call or other noises, most experts agree on two key functions听of birdsong: defending territory and wooing a mate. The better a songbird can show off vocally, the more likely it is to achieve its goal. In the Northern Hemisphere, male songbirds do most of the singing. Tropical species , as males and females often share performances.听
Although most songbirds usually stick to the same basic template for a song, individuals occasionally throw in an additional note or a change in pitch. These variations might sound novel and exciting, and help draw more mates. 鈥淭here鈥ll be an innovation, which is apparently quite attractive to females, and that innovation will then spread like wildfire through the whole population,鈥 says Heather Williams, a biologist at Williams College. 鈥淟ike anything trendy in human culture, they can shift things from generation to generation, or within generations for birds that keep on learning as adults.鈥澨
As a result, songbird melodies are always evolving. Most White-throated Sparrows in western North America used to sing Oh sweet Canada Canada Canada until a new tune took off over the past two decades. Now, they sing Oh sweet Cana Cana Cana.
On the flip side, some songbirds don鈥檛 have songs at all, says Kroodsma, who points to the example of a Common Raven. 鈥淚t belongs to the songbird taxonomic group, but it really doesn鈥t have a song.鈥 To make matters more confusing, there are non-songbirds with elaborate vocalizations. 鈥淚 hear flycatchers doing a lot of things that sure sound like songs to me,鈥 he says.听
So, to recap, not all songbirds are talented vocalists or even sing, and not all birds that sing are songbirds. If you want to听impress your friends, however, you can tell them that true songbirds are also called oscines, and听they have exceptional control of a special organ called the syrinx. Or,听instead, just relax, don't overthink听it all,听and enjoy nature's symphony.听