Noise pollution can harm birds even before they hatch

The raucous din of modern life can seriously mess with animals (SN: 2/9/15). Traffic noise can drown out mating calls, spike stress hormones and even increase mortality. Now, new research suggests some critters can be harmed by this noise even before they can hear it.

Zebra finch eggs and nestlings exposed to everyday traffic noise experience significant, lifelong reductions in health and reproduction, researchers report in the April 26 Science. These harms stemmed from direct exposure to the sound itself, the researchers say, suggesting noise pollution poses a more pervasive threat than previously thought.

“We were really surprised,” says Mylene Mariette, a behavioral ecologist at Deakin University in Geelong, Australia. “Not just because the effects were strong, but they lasted a long time.”

Earlier research linked noise exposure during development to health problems later in life, but scientists couldn’t rule out whether it was because noise messed with parenting. 

Mariette and colleagues manipulated the sound environment of zebra finches (Taeniopygia guttata castanotis) pre- and postnatally, exposing them overnight to traffic noise or birdsong as either eggs, chicks or during both life stages. Crucially, nestlings were separated from their parents for the sound treatments.

Traffic noise at only the egg or hatchling stage had detrimental effects, and it was worse for birds exposed to the sounds at both stages. Noise-exposed eggs hatched less often than song-exposed eggs. Twelve days after hatching, noise-exposed birds were 14.5 percent lighter, on average. And telomeres, the repetitive sequences of DNA at the tips of chromosomes, were also 38 to 46 percent shorter, on average, for noise-exposed birds. Shorter telomeres can indicate higher physiological stress (SN: 7/9/16).

The impacts extended to adulthood. In an enclosure where zebra finches were allowed to breed freely, noise-exposed birds produced 59 percent fewer offspring — roughly four fewer birds — than those raised amid natural sounds. The effect was attributable mostly to prenatal exposure, the team found.

Altogether, the results suggest “an innate and spontaneous response to noisy stimuli,” Mariette says. Precisely what underlies this response remains unclear, she says, but “it’s something that’s likely shared across species.”