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As anyone who has tried to hold a conversation in a noisy room knows, it is sometimes easier to rely on hand gestures than to shout over the din. White-throated dippers face a similar challenge along the fast-flowing streams they inhabit, where the roar of fast-flowing waters can sometimes drown out their melodic songs. Rather than trying to out-sing the river to defend territory or attract mates, these plump, endearing birds sometimes switch strategy entirely—turning to sight instead of sound, by flashing their bright white eyelids in a striking visual display.

A new study led by researchers from the Max Planck Institute for Biological Intelligence and Lancaster University is among the first to document this kind of sensory shift in a wild bird. The findings shed light on how dippers adapt their communication depending on social and environmental cues—and how such flexibility may have evolved in response to noise. The paper is in the journal Current Biology.

In the upland areas where white-throated dippers live, their varied, high-pitch metallic song is one of the earliest signs of spring. Sometimes seen perched on river rocks or skimming low over the water, these birds make their homes beside fast-flowing streams—ideal for feeding, but often difficult for communication, especially after heavy rains.

In a recent study of wild dippers in Britain's Yorkshire Dales National Park, researchers found that when river noise increases and other dippers are nearby, the birds don't necessarily raise their voices. Instead, they may blink more conspicuously, fluttering their white-feathered eyelids, which stand out against their dark-brown plumage. These visual cues, the authors suggest, may help attract mates or signal presence to rivals that might otherwise miss them—and reveal how the birds can fine-tune their use of sound and sight in real time to navigate their noisy world.

"Dippers don't just add visual signals on top of their songs—they seem to switch between them depending on the situation," says Léna de Framond, first author of the study.

"When the river gets louder and other birds are nearby, they blink more often. We even found that birds that blink most often don't sing as loud– suggesting a shift to visual communication. But when they are alone, we saw they actually tend to sing louder to rise above the noise. That contrast tells us the behavior is social, not just a response to sound, and is a rare example of a noise-induced multimodal shift in a wild animal."

Evolution shaped by river noise

Using more than one sense to communicate can be a big advantage in noisy environments. However, while many animals are known to adapt within a single sense—for example, by singing louder, changing pitch, or repeating themselves—clear evidence of animals switching between senses to send messages, like moving from sound to sight, or touch to smell, is still surprisingly rare.

The white-throated dipper made an ideal test case: it lives year-round beside fast-flowing rivers, where background noise is often high, and it has bright white eyelids that can act as a visual signal. If any species had learned to shift between senses to get its message across, the researchers reasoned, the dipper would be a great candidate.

The team spent more than 300 hours observing wild dippers, some marked with colored rings for identification. Through detailed observations, calibrated audio recordings, and statistical analysis, they uncovered one of the clearest examples yet of animals switching between senses to communicate.

"The study sheds light not just on how dippers communicate, but on how environmental challenges—like noisy rivers—can shape the evolution of signaling," says Henrik Brumm, whose group at the Max Planck Institute for Biological Intelligence led the research. "What's particularly interesting is the complexity of the dipper's behavior and its ability to adapt to changing conditions.

"It also raises new questions about how species balance clarity and complexity. More signals can help get attention, but also increase the risk of being misunderstood—and signals need to match the senses of the animals they're meant for. Now that we've seen this ability in dippers, it suggests that switching between senses may be more common in nature than we realize. In that sense, we may be seeing just the tip of the iceberg—and it's exciting to think about where this research could go next."