Cardinals Change Their Tune During Rush Hour
Northern cardinals, like other songbirds, change their tune when confronted with noise pollution. During rush hour and in other noisy environments, the birds will increase the frequency of their calls. But these strains sung over the din aren't as effective, say biologists at George Mason University in Virginia.
Using a computer, the biologists generated two cardinal songs -- identical except for normal and high frequencies -- to match what birds would hear in the wild. By hooking up an iPod to a speaker, the biologists then played their synthesized tunes to 26 cardinals.
The birds were less engaged in their responses to the higher-pitched warbles -- they sung back fewer times and did not fly past the speaker as frequently. Any benefit to being heard over rush hour traffic and other noise, the authors write, "might be lost" by these lower response rates. Not even the birds, it seems, like hearing one another shout over honking horns.