Birds use vocalizations and songs to communicate with each other. But is there a universal language that all birds share? Scientists have been studying bird vocalizations for decades trying to answer this question.
How do birds communicate?
Birds primarily use vocalizations, or bird calls, to communicate. Some examples of reasons birds vocalize include:
- Defending territory
- Attracting mates
- Warning others of danger
- Identifying themselves to others
- Keeping groups together
- Coordinating hunting
- Communicating at the nest
Bird species have specific repertoires of calls that they use. However, there are some commonalities across species in the types of calls used for certain behaviors.
Evidence for universal features
Studies have found some evidence that birds may have universal ways of conveying certain messages, even across species. Some examples include:
- Alarm calls – Many species have specific alarm calls that signal danger. These calls tend to be short, loud, and high-pitched.
- Food calls – Some species have distinct food calls that attract others to a food source. These tend to have a repetitious quality.
- Contact calls – Birds use contact calls to keep groups together and signal individual identity. These tend to be simple, quiet, and frequent calls.
- Parent-offspring interaction calls – Many species use common sounds like twitters and whisper songs to communicate at the nest between parents and chicks.
Researchers have experimented with playing calls of one species to another and observing the reactions. For example, many species will react to another’s alarm call by scanning for danger, even without prior experience with that particular species’ calls.
Evidence against universal language
While there seem to be some universal patterns, there is also substantial evidence that birds do not have a fully shared language:
- Songs are learned, not innate – Songbirds learn their species-specific songs from adult tutors while they are young. This learning is critical for their courtship songs.
- Calls vary across species – While there are similarities for types of calls, the details of the calls vary enormously across species. Each species has its own dialect.
- Meanings can differ – Calls that are used in similar contexts, like alarm calls, may convey subtly different meanings between species. So the calls are not perfectly interchangeable.
- Local dialects – Bird calls vary not just at the species level but also geographically within a species, akin to local dialects.
Taken together, this evidence indicates birds do not have a universal shared language. While there are universal patterns, particularly for basic call types, the specifics differ across species and locations.
Case study: Chickadee mobbing calls
Research on chickadee mobbing calls provides an example of how birds combine universal signal types with species-specific differences.
Many bird species make “mobbing calls” – loud, frantic calls – when they detect a predator and move to harass it. This recruits other birds to mob the intruder.
Black-capped chickadees have a simple mobbing call that sounds like “chick-a-dee”. They use this alongside other vocalizations and nonvocal sounds like wing snaps.
Experimenters have played mobbing calls of other species to chickadees. The birds react as if their own calls were played. However, their response is stronger when hearing a chickadee call compared to another species’ call, indicating they do distinguish between them.
Other studies found geographical variation in chickadee mobbing calls across North America. Calls vary in features like pitch and note duration. This local signature information could allow birds to distinguish familiar and stranger birds.
So while chickadees identify mobbing calls of other species as signaling danger, they still prefer their own dialect over others. This shows how a universal call type interacts with species and geographic variation.
Neural basis
How do birds’ brains enable learning complex communication signals? Songbirds like sparrows and finches have provided insights.
Parts of the avian brain are specialized to learn and produce songs. Forebrain song nuclei control song learning, while motor nuclei control the physical production of song.
Birdsongs originate in the syrinx vocal organ but are controlled by neural circuits between forebrain and brainstem regions. Juveniles require auditory experience to shape their developing neural circuits.
While we still lack a full understanding, the neural specializations for vocal learning may enable songbirds to both learn species-specific songs and identify universal signals like mobbing calls.
Implications for evolution
The origins of avian vocal communication have been traced back over 50 million years. Studies suggest vocal learning originated just once early in songbird evolution.
If most songbirds possess the same brain structures for vocal learning, how did such diversity in birdsong evolve? One theory is that small initial differences in calls were exaggerated over time via sexual selection or dialects. Regions of the brain dedicated to vocal learning allowed birds to expand beyond innate calling types.
Researchers propose that vocal learning was crucial in enabling diversification into the thousands of songbird species that exist today. It allowed greater flexibility than innate call systems. This may have facilitated adapting to new environments and social interactions as species spread geographically.
Conclusion
In summary, evidence shows birds use some consistent vocalizations like alarm and food calls across species. However, they lack a true universal language. Complex learned songs and local call variations are specialized to species and populations.
Universal signal types may reflect ancestral starting points that evolved into diverse, specialized dialects and songs. This diversity underscores birds’ vocal flexibility, which continues to inspire human engineers seeking to mimic avian vocal abilities.