[The Language of Birds] Listen! The world is full of sounds. [Laughing] [Airplane noise] [Symphony tuning up] Many sounds are familiar to us [phone rings] and when they’re familiar [phone rings] you know what to do when you hear them. [phone rings] Hello? [foreign language] Nature is also full of sounds. Though these sounds may not be familiar to most people, they can be understood by other animals. When you hear this [Thrush bird call], it’s not just in noise; it has meaning that the bird is trying to communicate. In this case the Thrush is saying: hello, I’m here. I’m alright. Each bird can communicate several different messages. For instance, the common Northern Cardinal can say, This means, I’m hungry; the children are hungry; bring food. In a Cardinal family, parents and young make this soft chipping sound to coordinate movements in vegetation without giving their location away to predators. An adult male uses this call to shoe fledglings away from a nest when a new brood of eggs hatches. And this male is singing to attract a mate. Of course, there are many, many different species of birds. Each communicating with different sounds. Here for instance is a Swamp Sparrow singing for a mate. [Bird song] This trilled song is extremely difficult to make. The healthier the male, the wider the pitch range and the faster the trill. So female Swamp Sparrows can tell from the song which bird is in the best physical condition and thus most desirable. [bird song] Northern Mockingbirds know hundreds of different songs. A typical male will sing one song three to four times, switch to the next song without pause, and so on for long periods. The more songs he can sing the older and more established he is likely to be. [Bird song] The song of the Veery is a haunting two-toned descending spiral [Bird song] How does it do that? Birds can make such complicated sounds because of the unique structure of their instrument. [Music] We humans push air from along through vocal box call a larynx that vibrates making a single sound. [Singing] We adjust pitch and tone both at the larynx and by the shape of the mouth. [Singing] Birds have a similar structure, but it’s doubled. The syrinx of a song bird has two membranes allowing it to make separate sounds at the same time. [Bird song] Every species has its different physical variation that helps it make it song. [Bird song] In the cloud forest of Central America, the three-wattled Bell Bird makes itself heard by swelling and contracting the muscles on its neck and back. Heaving its chest, opening its beak incredibly wide, and releasing a “bonk” that can be heard for more than half a mile. [Bird song “Bonk”] [Bird song “Bonk”] [Bird song “Bonk”] The sounds that birds make also relate to their environment. A bird who lives in open fields can have a fast complicated song like this Bobolink. [Bird song] A bird that lives in a forest needs a sound that can project through trees and branches; sometimes loud and piercing; [Owl hooting] sometimes deep and low. [Bird song] But where is the bird? Is it in a tree or on the ground? Sometimes you can hear birds before you see them. Sometimes your ears are better tools in your eyes. Here in the rainforest branches are so thick that you can’t even see birds when they’re flying. So we listen to know who’s there. There’s this duet between a pair of Grey-breasted Wood Wrens. [Birds singing] A Black-faced Solitaire whistles this serial song. [Bird song] If you listen very carefully, you could identify more than fifteen species here even though you couldn’t see a single one. [Birds singing] [Music] The same is true in your neighborhood. [Dog barking] [Cars, honking] [Birds singing] [Baby crying] Sometimes you have to use your ears to know who’s there. Like this Bluebird. [Bird song] Some species don’t even sound like birds. This is a cat bird. [Bird call sounds like a cat meow] You have to listen well to hear the different types of bird sounds and just as you have learned to understand that this, [Phone rings] means you should answer the phone. Or that this, [Sirens] means you should get out of the way, you can learn to understand the sounds that birds make. Like this scream of the Red-tailed Hawk which means, this is my territory keep out! [Red-tailed Hawk call] When you understand these sounds you know more about the world around you. It all starts with listening. [Various bird calls] [Music]

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When you hear that “tweet, tweet” up in a tree, it’s not just a pretty noise—the bird is trying to send a message. This animated video explores how and why birds communicate using sound. From the soft notes used by Northern Cardinals to keep in touch, to the fast trills of a Swamp Sparrow attracting a mate, birds use sound to send all sorts of messages. Their specialized voicebox, or syrinx, helps them do it, allowing birds to sing complex songs quickly. From the woods to the grasslands you hear birds wherever you go, and once you tune in you can begin to decode the language of birds.