In the column Since You Asked in every issue of BirdWatching, Contributing Editor Julie Craves answers readers’ questions about birds and bird behavior. Here’s a question from our August 2017 issue.
Why do some diurnal birds sing at night? — T. N. Roman, Columbus, Georgia
In North America, mockingbirds are famous nighttime songsters, as are Common Nightingales of the Old World. A primary reason male birds sing is to attract mates, and it has been found that unmated mockingbirds and nightingales sing at night more frequently than mated males. Until relatively recently, not too many other species of diurnal songbirds were known to regularly sing at night.
In the last decade or so, researchers have determined that more bird species are singing at night in urban areas so that they do not have to compete with ambient noise such as traffic sounds that are more common in the daytime. In addition, some species have started singing earlier in the day or have increased the volume of their songs in noisy places.
Not only is human-created environmental noise often simply loud, but it tends to be generated at lower acoustic frequencies. A number of species, including Song Sparrow and House Finch, have been found to sing with modified acoustic frequency in response to human-generated lower-frequency noise, reducing the masking of their lower-frequency notes by ambient clamor.
Being heard clearly is important to birds for mate attraction, territory defense, and communicating threats to other individuals. Noise pollution has had similar impacts on other types of creatures, including amphibians and insects.
About Julie Craves
Julie is supervisor of avian research at the Rouge River Bird Observatory at the University of Michigan Dearborn and a research associate at the university’s Environmental Interpretive Center. She writes about her research on the blog Net Results, and she maintains the website Coffee & Conservation, a thorough resource on where coffee comes from and its impact on wild birds.
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