Last week, I wrote about the noted affects of noise on the iconic pinyon tree of the American Southwest Mesas. In all, the deterioration of the pinyon is already adversely affecting about 1,000 species of fungi, insects, arthropods, mammals and birds depend on tree for their survival.
This week, new findings are beginning to prove that noise pollution is interfering with the reproductive choices of birds as well. Male birds are the crooners in nature; the tone of their song plays a critical role in the mating protocol of most feathered species. Birds in urban communities and communities exposed to high decibel traffic and industrial noise are singing and chirping in a different tune than that which nature provided, in order to be heard above the din of the manmade noise with which they must now compete. In the process of changing their singing tone to be able to hear one another, they are losing their natural key - their specific mating call that serves to attract females. If they were to quit fighting the noise and maintain their natural singing voices, chances are they won’t be heard by potential mates at all.
According to Wouter Halfwerk, a behavioral ecologist at Leiden University in the Netherlands, lower frequency singing among male song birds has the vibe that brings the lady birds calling. Let’s call it the Barry White songbird vibe. When given the choice between a low pitched Barry White vibrato and, say, a high pitched Barry Gibb staccato, the lady birds choose Barry White every time.
“If females can hear all song types equally well, they will go for the sexy ones,” Halfwerk says. “But if they cannot hear the sexy ones well anymore, then they might just go for the songs they can still hear.
"It could very well be that noise pollution is interfering with reproductive decisions by females."
However, females are working a little harder than they used to, to identify quality mates who are practicing their sexy voices and keeping them in tune. Halfwerk, along with a group of scientists studying the effects of manmade noise on animals, did some spying and discovered that certain females may be canoodling with another male on the sly if their own mate’s singing tone isn’t doing it for them.
Apparently these untrustworthy female birds are sneaking out of the nest in the early morning hours, chasing after a nearby Barry White crooner – a rendezvous which for birds only takes about 60 seconds – and she’s back in the nest, never missed. That’s right – researchers surmised that the males that sang in higher (Barry Gibb) registers were more likely to be cuckolded than the low-throated crooners.
Since they wouldn’t be real researchers if they didn’t consider every opportunity to challenge their hypothesis, the scientists conducted paternity tests on the offspring and discovered that about 30% of the nest-dwelling partner males were not the baby daddy. Overall, the males that sang in new, high pitched frequencies to be heard above the manmade noise – most notably around the time that the lady birds were at their most fertile – were the males that ended up unwittingly helping to raise another bird’s offspring.
Next, these same researchers fitted nests with microphones and speakers, and tracked the females while they were subjected to different recordings of their mates’ calls. The researchers also funneled in noise that mimicked traffic sounds to see if it had any effect on the females.
With urban noise in the mix, the females responded to their mates' high-pitched calls more often than the lower, sexier (Barry White) calls — probably because they could hear them better.
The results of these studies have confirmed that while noise pollution does interfere with the birds' ability to communicate during their high-stakes mating games, they’re still managing to mate. Still, previous studies have shown that a variety of birds can suffer when they change their songs, according to Erin Bayne, an ornithologist at the University of Alberta. The new study is one of the first to explain why.
As more research data is completed on the effects of manmade noise on animals, nothing is being done to temper noise pollution, which is as insidious to human health as it is to a bird on the wire.