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article imageUrban birds sing louder, longer, to overcome city noise

By Igor I. Solar     Apr 18, 2011 in Environment
Toledo - A team of Spanish scientists has found that birds increase the amount of time they spend in vocal activities to counter the sound intensity from human activities, especially the noise caused by city traffic.
The researchers recently published the results of their study in the March-April issue of the journal “Behavioral Ecology”. The report describes the singing behaviour of the European serin (Serinus serinus) in a suburban area of the city of Toledo, where the species is common and experts were able to carry out controlled measurements of the bird’s singing activity.
The study led by Dr. Mario Díaz of The Spanish National Research Council (CSIC) revealed that, as the city noise increases, the serin spends up to 60 percent of the time singing. The response to noise pollution correlates with environmental noise level up 70 decibels (dB). When the city noise increases beyond that level, the serin’s singing effort no longer adjusts. The flexibility of the serins also allows adjustment of vocal activity taking into account the noise levels in different days of the week. On weekends, when the noise level in the city is lower, the birds sing less.
A European serin in water
A European serin in water
J. Coelho
The ecological significance of bird singing relates to territorial marking, attracting females and deterring potential competitors. Another function of singing, which even involves the recognition of “dialects” within species, allows birds to stay in touch with their own kind.
The fact that the serins suspend their effort to compete with environmental noise levels beyond 70 decibels suggests that the strategy has a physiological and survival cost. The serins are able to recognize that attempting to overcome noise levels higher than 70 dB is not worth the effort.
A male nightingale
A male nightingale
J. Dietrich
"The bird has to spend some time monitoring the environment. While singing they are less aware of predators or the arrival of competitors," said Diaz to ElMundo.com (in Spanish).
“Because singing time may trade off with vigilance time, our data suggest that bird populations in noisy city environments may face an increased challenge for survival compared with quiet areas,” say the researchers in their report.
The serin, a small bird closely related to the canary, inhabits lands around the Mediterranean Sea, Central Europe and North Africa. For long time it has been regarded as mostly adapted to gardens and rural environments. However, more recently has been found successfully expanding its range to occupy city environments.
An urban great tits (Parus major) on a branch
An urban great tits (Parus major) on a branch
Luc Viatour
The results of this research support previous studies on the adaptation in singing behaviour of songbirds, such as the “nightingale” and the “great tit”, in response to anthropogenic noise.
Noise pollution in urban areas has long been an increasing problem for city dwellers. The World Health Organization (WHO) has determined that night-time noise level beyond 30 dB can interfere with sleeping, and 70 dB, commonly found in industrial, commercial shopping and traffic areas, is enough to cause hearing impairment in humans. A vuvuzela, the plastic horn instrument popular at soccer matches in South Africa, can generate sound levels as high as 130 dB.
More about Songbirds, City noise, environmental noise, sound pressure, decibels
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