15 March 2019

Bird Talk Revisited

Welcome back. Do you have a pet bird? Are you a birder? At present, I answer no to both. On my last visit to Upstate New York, I did spend time with my brother and sister-in-law, with their cockatiel roaming about. I also toured Cornell’s Lab of Ornithology (wow!), which I hadn’t been to in at least 30 years.

Peacock from
Bird Talk.
I’ve blogged about birds on occasion (see P.S.). One post reviewed a study that found peacocks use their feathers to communicate in the infrasound--frequencies we (i.e., humans) can’t hear (Bird Talk).

But what about the screeching, chirping, tweeting, singing and cawing we can hear?

Bird-Call Syntax
Humans do pretty well with syntax, the sequence in which words (or linguistic elements) are put together to form meaningful sentences. Through compositional syntax, we’re able to express unlimited meanings from a finite number of words.

Japanese tit (Parus minor) (from
The first experimental evidence for compositional syntax in a wild animal species, a passerine bird, the Japanese tit (Parus minor), was provided in a 2016 study by researchers affiliated with Japan’s Graduate University for Advanced Studies and Rikkyo University, Sweden’s Uppsala University and Switzerland’s University of Zurich.

They found the birds produce complex vocalizations composed of different types of notes. When approaching and mobbing predators, for example, their calls contain mainly four notes that might be labeled A, B, C and D. Typically, the bird produces A, B and C notes in combination as AC, BC or ABC calls, while it strings together seven to ten D notes in a D call.

Sound spectrogram of Japanese tit notes in ABC-D
(from www.nature.com/articles/ncomms10986).
Although the D call is produced alone in non-predatory contexts, in predatory contexts, D notes are often combined with other note types, typically at the end of note strings, such as ABC–D calls.

Monitoring the bird response to audio playbacks, the researchers observed the birds scanned the surroundings when hearing ABC calls, approached the sound source (to check it out) when hearing D calls, and both scanned and approached on hearing ABC–D calls, suggesting the D notes modify the meaning of ABC calls as in compositional syntax.

That interpretation was supported when the birds failed to produce a compound response to playbacks of an artificially reversed ABC–D call, produced as a D–ABC call.

Bird Calls Convey Mental Images

The lead author of the 2016 study, now at Kyoto University, took bird communication a step further in a more recent study.

Words often produce mental images. Suppose I told you about the time Vicki and I were walking on the path in the woods behind our house in Northern Virginia, when she stopped and pointed to the slender green snake hanging from a branch, shoulder height, just off the path. Do you picture the snake?

It depends how you feel about snakes and how well I conveyed the image, but it seems that Japanese tit calls convey a visual image when it counts.

The bird is known to produce specific calls when and only when it encounters a predatory snake.

The researcher hung a wooden stick so it could be moved like a snake climbing a tree, or he just pulled the stick along the ground.

Japanese tit on branch approaching snake-like
stick being pulled up the tree
(from video
www.youtube.com/watch?v=1ajyNRqf-fY in www.nature.com/articles/ncomms10986).
When the birds heard an audio playback of their snake-specific alarm call, they became more visually perceptive to objects resembling snakes and approached the wooden stick as if it were a snake. If the birds heard calls other than the snake-specific alarm or if the stick wasn’t moved like that of a snake, the birds did not respond.

In essence, before detecting the snake, the birds retrieved a visual image of the snake from snake-specific alarm calls and used it to search.

Wrap Up

The 2016 study suggests Japanese tits and presumably other birds have developed compositional syntax rules. Should we expect the same from other animals?

Unrelated to syntax, the study of a bird call-induced visual search image opens a new area in animal communication.

Thanks for stopping by. I hope you found it interesting. Feel free to tweet about it.

2016 study on bird syntax in Nature Communications: www.nature.com/articles/ncomms10986
2018 study on bird calls evoking mental image in Proceedings of National Academy of Sciences: www.pnas.org/content/115/7/1541
Article on 2018 study on National Geographic website: news.nationalgeographic.com/2018/02/japanese-songbirds-process-language-syntax/

Warren’s earlier blog posts on birds
- parakeet I had in grade school:
- homing pigeons:
- crows:
- chickens:
- herons drop bait to attract fish:
- peacock communication:
-some of my daughter Rachel’s bird photographs:
- bluebird nesting boxes (sorry, no bluebirds):

A version of this blog post appeared earlier on www.warrensnotice.com.

No comments: