Singing under glass: rapid effects of anthropogenic habitat modification on song and response behaviours in an isolated house sparrow (Passer domesticus) population

Anthropogenic noise pollution and the introduction of novel infrastructure
can impose strong selective pressures on avian communication by affecting
the efficacy with which acoustic signals are transmitted and received.
Many species have now been shown to sing at higher frequencies in noisy
urban environments. However, few studies have investigated the effects of
signal modification on the response behaviours of receivers, and fewer
still have been able to indicate the timescale over which these changes in
pitch have occurred. We compare vocal communication between house sparrows
(Passer domesticus) that reside within the world’s largest, single-span
glasshouse (completed in the year 2000), and house sparrows directly
outside this glasshouse, in open farmland. The glasshouse contrasts both
acoustically and physically with the external environment, low frequency
background noise being significantly louder inside than outside. We show
that minimum song frequency was significantly higher inside the glasshouse
than in surrounding farm habitat. Using song playback, we also found that
birds within the glasshouse reacted more strongly to playbacks from the
glasshouse habitat than they did to playback of song from farm birds
outside. The degree of difference in frequency is similar to that shown
for other bird species between urban and rural environments, demonstrating
that such behavioural differences may arise over a relatively short time
period (14 years in this case)