The sharp-eyed chickadees in our yard have something to say when I come out to fill our bird feeders. “Dee-dee-dee!” they call. “Dee-dee-dee-! Dee-dee-dee!” as they land on a branch directly over my head. As it happens, they are most likely speaking in “Chickadese”, a highly-evolved bird language with “words” arranged in sentences.
Animal communications researcher Todd Freeberg, of the University of Tennnesee-Knoxville, has discerned words and sentences uttered in context by Carolina Chickadees, close cousins of our Black-capped Chickadees. The two species have similar repertoires of songs and calls. Chickadees have a high diversity of calls and Freeberg identifies seven known note types, three of which are “D”, “A” and “C”. Those birders attempting to learn bird calls known that it is best to be able to identify a chickadee voice, rather than a specific song, since individuals sing a variety of songs.
Chickadees hang out in conspecific flocks and often mixed-species flocks. In our yard this winter, we have five chickadees that visit our feeders together, and usually appearing with white- and red-breasted nuthatches, downy woodpeckers, house finches, goldfinches and juncos. Thus, if they want to communicate, there is always an audience.
Freeberg discovered that the D “word” is uttered when a predator appears. A repeated D, like “dee-dee” means that a perched predator is around. Small predators, like screech owls, pose a greater threat to tiny chickadees than big predators (like a great-horned owl) and their presence renders a more emphatic “Dee-dee-dee!” than a big one, which might only get a “dee!”
But Ds also indicate food sources, and a food source new to a flock triggers many Ds: Dee-dee-dee! Dee-dee-dee! And this call quickly attracts more birds than a single dee! Freeberg thinks that Ds are a signal for recruitment, calling other chickadees to a spot, either to feast on the food, or to mob a sitting hawk or owl.
The “A” word is given when a hawk flies through a flock, and increases with escalating danger. Freeberg labels this an alarm call. It is a signal for birds to scatter. Freeberg has run experiments with hawk models flown overhead, and harmless blue jay models by comparison. Hawk models elicit more “As.”
The “Cs” are produced when the chickadees are in flight. Freeberg has released captured chickadees and recorded the Cs as the birds fly away. The C note indicates a bird is moving.
All these notes can be combined to encode information about movement, recruitment and predator presence simultaneously. Chickadees rely on a highly-evolved, complex communication system to help them navigate their world. Furthermore, these “words” are arranged in “sentences” following strict rules of “grammar.” “A” and “C” notes are always at the beginning of a sentence; “D” notes are only at the end. Chickadees don’t break these rules. Less than .4% of all calls recorded arranged the notes in a different order.
Freeberg asks other questions of his Carolina Chickadees: What are the social dynamics of their mixed flocks? Do the sentences change in different habitats? Do they distinguish between different predators—Cooper’s Hawks versus Shrikes? What drives the evolutions of this language?
Perky little chattering chickadees are some of my favorite birds. In the future, I will listen carefully to understand what they are telling me.
Information for this article was taken from a blog post by Harrison Jones, Masters student in the Wildlife Ecology and Conservation Department at the University of Florida, available at <blogs.ifas.ufl.edu>
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