When it gets too noisy, male eastern bluebirds (Sialia sialis) will alter the loudness and pitch of their songs. Like us, they start shouting, and in real-time too, according to new findings published in Integrative and Comparative Biology.
Previous studies have shown that birds in noisy places tend to sing differently than their counterparts living in quieter areas. But it’s been unclear just how immediately these shifts happen. Can birds make quick vocal adjustments when, say, a truck or a plane passes by? To investigate, University of Exeter’s Caitlin Kight and John Swaddle from the College of William & Mary recorded songs produced by 32 male breeding bluebirds. They analyzed two songs from each male – one sung during the quietest moments of ambient noise in his nest box, the other during the loudest – to observe what changes occur between the different noise levels.
Male bluebirds, they found, were able to both perceive and respond to changes in noise level. As it increased, the birds produced songs that were louder and with a higher pitch, making them more likely to be heard by potential mates and rivals alike. Furthermore, they would modify their songs immediately after the clamor intensified – the first time real-time modifications have been observed in a member of the thrush family Turdidae. So far, we know of only five other birds that can do this.
"Although many manmade noise regimes are often very different from those found in nature, there can be surprising similarities in certain features, including volume, pitch, or timing," Kight explains in a statement. Traffic sounds share a lot in common with waterfalls and strong winds, for example. "Animals that evolved in habitats with those natural features may therefore already have, within their existing repertoires of behaviors, the flexibility to respond to noise pollution." But that doesn’t mean the impacts of noise pollution aren’t adverse. "Unfortunately," adds Swaddle, "the world is getting so noisy that even the most flexible of species will eventually reach a threshold beyond which they will have difficulty communicating, which will impact their ability to breed successfully."