A new study that examined the effects of urban cacophony on house sparrows drew a pretty depressing conclusion — urban noises can interfere with the calls between songbirds and their chicks, meaning that chicks reared in the city are less healthy than their counterparts chirping and fluttering around in bucolic bliss.
David Lofink of Discovery Magazine writes about a study performed by the University of Sheffield's Julie Schroeder, who found that loud noises drown out communication between mother house sparrows and their chicks, including the calls chicks make to beg for food. Lofink explains that only a handful of other studies have examined the effect of loud noises on songbirds mating and nesting habits, though none have quite tackled the serious maternal questions raised long ago in Are You My Mother?
The other thing that makes Sheffield's study unique is that she focused on a well-known group of sparrows living on Lundy Island. These sparrows regularly trade swap their eggs among nests, which results in some sparrows becoming unwitting surrogates for chicks they're not related to. This phenomenon helped Sheffield separate the effect of a sparrow's parentage from the effect of its environment, just in case the genetically weaker sparrows were somehow more prone to live next to a roiling electrical generator, which, conveniently, is exactly what some of them were doing. The generators on Lundy Island (built in 2001) run continuously from 6 to 9 pm and emit 70 decibels of noise, "about as much," muses Lofink, "as a rowdy primary school classroom."
Schroeder compared the nest boxes located in the generators' noise zone to nests located in a quieter zone. She figured out that, while the noise has no real effect on the health of adult birds (female birds could even lay the same number of eggs), it did adversely affect chicks. Though chicks in quiet areas had a 25 percent chance of living long enough to fledge, the chicks in noisy areas had only a 21 percent chance. Plus, those urban chicks weighed less than their country counterparts, most likely, Schroeder believes, because mother birds visited their chicks less often and provided them with less food.
If right about now you're picturing a forlorn little baby bird wailing in his nest, sorry — it's a total bummer. The fact that adult birds seemed in fine health led Schroeder to single out noise as the culprit in the weakness of urban chicks, since, say, if pollution had been stunting chick growth, adults would have been unhealthy too. Schroeder thinks that her findings may help explain the house sparrow's sudden disappearance in Western Europe and North American. "If what we suggest takes place in big cities too," she says, "it is likely to play an important role in the sparrow population dynamic, and is probably one cause of the dramatic population crash that we are currently observing."
Lofink reminds us that the exact cause of the chicks' undernourishment is still uncertain — there may very well be a barrier between mother and chick communication in urban areas or loud noises may scare off all the delicious insects. It's probably pretty important, though, for us to keep track of the plight of these songbirds, lest the hideous pigeon become the only bird we can look forward to seeing on our stroll to work in the big city.
Urban noise can turn sparrow females into bad mothers [Discovery Magazine]
Image via David W. Leindecker/Shutterstock.