do birds have a language

The grammar of bird calls

Semantics, the relationship between words and meanings, is a fundamental component of human language. Scientists had long believed that animal vocalizations, in contrast to human speech, were involuntary and simply expressed the animal’s emotional state without providing any additional information. However, a wealth of research conducted in the past forty years has demonstrated that different animals have unique calls with distinct meanings.

Many bird species use different alarm calls for different predators. Japanese tits, which nest in tree cavities, have one call that causes their chicks to crouch down to avoid being pulled out of the nest by crows, and another call for tree snakes that sends the chicks jumping out of the nest entirely. Siberian jays vary their calls depending on whether a predatory hawk is seen perching, looking for prey or actively attacking — and each call elicits a different response from other nearby jays. And black-capped chickadees change the number of “dees” in their characteristic call to indicate the relative size and threat of predators.

According to two recent studies, some birds’ vocalizations may have meaning depending on their order. This could represent a basic version of the rules governing the arrangement and combination of words and elements in human language known as syntax, though the idea is still controversial. This is demonstrated by the well-known “dog bites man” vs. “man bites dog” example.

In addition to alert calls, many bird species use recruitment calls that summon other members of their species. Both Japanese tits and southern pied babblers appear to combine alert calls with recruitment calls to create a sort of call to arms, gathering their compatriots into a mob to harass and chase off a predator. When the birds hear this call, they approach the caller while scanning for danger.

Researchers at Kyoto University, led by ethologist Toshitaka Suzuki, found that the Japanese tits are affected by the sequence in which the combined calls are made. An artificially reversed “recruitment alert” call did not cause the same level of mobbing response as when Suzuki’s team played a recorded “alert recruitment” combo to wild tits. The scientists devised a cunning method to test this theory, though it could just as easily be explained by the fact that the birds responded to the combined alert recruitment call as their own signal without understanding the components of the combination.

Japanese tits are also able to recognize and react to the unique recruitment calls made by willow tits in the wild. The Japanese tits reacted with the same combined scanning and approaching behavior when Suzuki’s team combined the willow tit recruitment call and the Japanese tit alert call, but only if the calls were placed in the proper alert recruitment order.

“These results demonstrate a new parallel between animal communication systems and human language,” Suzuki and colleagues wrote in Current Biology in 2017.

But behavioral neuroscientist Adam Fishbein of the University of California, San Diego says it depends on how one interprets the call combinations of the tits and babblers in relation to discussions of human language, which involves more complex sequences.

According to Fishbein, “you would get a whole bunch of different combinations of things if they were doing something more like language.” “It’s such a restricted system within the birds. ”.

According to Fishbein’s own research using zebra finch song, birds may not value syntax as highly as humans do. He remarks, “It seems like people are trying to impose this human conception of communication on what the birds are doing.”

Birdsong often follows typical note, syllable, and motif sequences and patterns, and it can be extremely complex. As a result, singing birds may be a more accurate representation of human language than tits’ alert and recruitment calls. Birdsong has parts that sound to the human ear like word syllables, so it’s natural to assume that the message depends on the order in which those parts appear. However, it may surprise you to learn that we have very little knowledge of how bird ear perception works with birdsong sequences. According to Fishbein’s research, humans may not always perceive the same sounds that birds do when they sing.

For his graduate work at the University of Maryland, Fishbein studied zebra finches that had been trained to press a button when they heard a change in sounds played to them. When the birds correctly identified a change, pressing the button got them a food reward. If they guessed wrong, the lights in their enclosure went off briefly. Fishbein tested what differences the birds are actually able to decipher, helping scientists understand what aspects of birdsong are important to the birds.

In one experiment, Fishbein and his associates repeatedly played the finches’ typical song at predetermined intervals before interspersing a syllable-rearranged version of the song. Although it is obvious to humans that something has changed, the birds’ ability to recognize the shuffled sequence was surprisingly poor.

The birds performed much better at another test Fishbein gave them. Within each song syllable, there are higher-frequency details called “temporal fine structure” that may be something like what humans perceive as timbre or tone quality. When the scientists messed with the song’s fine structure by playing one of the syllables backwards, the finches were “exceedingly” good at catching it.

They’re significantly more adept at hearing this aspect of sound than humans are, according to Fishbein. Therefore, when we merely listen to birdsong informally, we may not be tapping into this level of sound that they are. ”.

As with much scientific research, our comprehension of what birds hear and what matters to them is constrained by what we hear, and in this case, statistical analyses employed to parse birdsong, according to linguist Juan Uriagereka, who collaborated with Fishbein at the University of Maryland. “We had no idea what the units they were merging were ten years ago,” he claims. “And naturally, it’s our estimation as to what the units are, right?”

Despite the fact that male zebra finches only learn one song, researchers have discovered that there are differences in the temporal fine structure of different renditions of the same song, suggesting that the birds may have a far more complex communication system than previously thought. According to Fishbein, “it’s possible that the individual elements hold the majority of the meaning, so their arrangement may not have as much of an impact on meaning as it would otherwise.” ”.

Some of the best recent evidence for intentional communication in birds comes from observations of wild Arabian babblers at the Shezaf Nature Reserve in Israel. A team led by ethologist Yitzchak Ben-Mocha recorded adult babblers coaxing fledglings to move to a new shelter. Adults call and wave their wings in front of fledglings and then move toward the shelter. If a youngster doesn’t follow immediately or stops along the way, the adult comes back and does the song and dance again and again until the fledgling complies.

Signs of intentionality have been shown in many animals. Ground squirrels, Siamese fighting fish, chickens, and even fruit flies change their signals depending on who is around to receive them, an indication that they have some voluntary control over those signals. Other animals seem to intentionally “show” others something, like a dog who looks back and forth between a human and a bag of treats or a hidden toy, perhaps even adding a bark to get the human’s attention first. Ravens also appear to show objects to other ravens by holding them in their beak—usually only if the other bird is paying attention.

Jarvis examines songbird brains to learn more about the evolution of language. The brain stem, a region close to the spinal cord that controls automatic processes like breathing and heartbeat, contains a circuit that allows animals that only produce involuntary sounds to control the musculature that produces those sounds. “This new forebrain circuit for learned sounds has evolved in humans and songbirds, and it has taken over the brain stem circuit for innate sounds,” explains Jarvis.

Even though humans and birds are extremely different from one another—their last common ancestor lived over 300 million years ago—their vocal learning brain circuits are strikingly similar. Since our closest relatives, nonhuman primates, do not have a specific circuit for mimicking sounds, scientists have concluded that this ability did not originate from a common ancestor. In birds, it must have evolved independently; this is an illustration of evolutionary convergence.

His theory for how similar vocal-learning circuits evolved multiple times in distant species is that they were built from an adjacent circuit that controls the learning of some movements. “The spoken-language brain circuit in humans and the song-learning circuit in birds,” Jarvis argues, “evolved by a whole duplication of the surrounding motor pathway.”

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