As part of her research, Dr. Steffi LaZerte recorded both natural singing patterns of black-capped chickadees in quiet and noisy areas in different cities across B.C.
Just like humans learn to adapt communicating in urban noise, so too do black-capped chickadees.
Birds’ vocalizations play an important role in mate attraction and territory defence in a noisy, city environment.
As part of her PhD thesis in 2015, UNBC researcher Dr. Steffi LaZerte discovered that black-capped chickadees, which sing a single song type, can learn to pitch-shift this song up and down in frequency to compensate for noise from traffic in cities.
LaZerte’s findings have been published in a top-tier evolutionary biology journal, Proceedings of the Royal Society of London B. Her co-authors on the paper are her PhD supervisor from UNBC, Ecosystem Science and Management professor Dr. Ken Otter and their collaborator Dr. Hans Slabbekoorn from Leiden University in The Netherlands.
LaZerte was using different chickadee species to investigate a general phenomenon seen in how birds respond to urban noise which was first described by Slabbekoorn. He found that urban noise from traffic tends to be in the low-pitch register, and he also noticed that birds in cities tend to sing songs that are higher-pitched than birds in quiet, rural areas, presumably so that their songs are not masked as badly by the underlying noise.
Many studies have shown since then that this is a common trend for birds to converge on higher-pitched songs in cities.
“Black-capped chickadees are pretty unique in that while they sing a single song type, they naturally pitch-shift this song up and down in frequency,” said Dr. LaZerte. “But, what's really interesting is that birds in noisy areas have learned to do this deliberately to compensate for urban noise.”
LaZerte recorded both natural singing patterns of black-capped chickadees in quiet and noisy areas in different cities across B.C. In addition to simply recording them, she also set up speakers and broadcast synthetic traffic noise at them to see how they would respond to sudden increases in noise.
She discovered that birds do shift the frequency of their songs upwards in the face of low-frequency song, but that birds appear to need prior experience with noise in order to respond correctly to it. They need to learn how to cope.
When she played artificial noise to males in quiet habitats, they changed their songs in response, but they shifted them down a pitch (the wrong way) which would actually make them harder to hear.
Only those birds who were already living in noisy environments and who had prior experience dealing with noise showed the appropriate response when presented with artificial noise – they shifted their songs up in pitch.
A link to the paper can be found here: http://dx.doi.org/10.1098/rspb.2016.1058