Strategies of song adaptation to urban noise in the house finch: syllable pitch plasticity or differential syllable use?

Abstract

The influence of ambient noise in shaping birdsong attributes has received much attention lately. Recent work shows that some birds sing higher-pitched songs in noisy areas, which may allow them to avoid acoustic interference; yet it is not clear how this is achieved. Higherpitched songs may be produced either by using the same syllable types in quiet and noisy areas, but singing them at a higher frequency in the latter (syllable pitch plasticity), or by using different syllable types in silent and in noisy circumstances (differential syllable use).Here we explored both strategies in the Mexico City population of house finch (Carpodacus mexicanus), a species known to possess a repertoire of several hundreds of syllable types. Birds produced songs with higher minimum frequencies in noisy than in quiet areas. This was mostly due to the minimum frequency of some syllable types being higher in noisy areas than in quiet locations. Also, males modulated the minimum frequency of the same syllable type during momentary increases of noise. Our results can help explain the high success of house finches at colonizing urban areas, while providing evidence of syllable pitch plasticity.

Experimental evidence for real-time song frequency shift in response to urban noise in a passerine bird

“…Additionally, birds can increase the redundancy of signals so that the message has an increased chance of getting across in noisy environments [6], or sing at times when noise level is lower [7]. Another possibility is to sing higher pitched songs to reduce their acoustic overlap with low-frequency noise [8][9][10][11]. A recent study has shown that urban populations of great tits (Parus major) have an increased minimum frequency in comparison to the countryside populations, and that this modification is best explained as a response to noise perturbation [12].…”

Anthropogenic noise affects song structure in red-winged blackbirds (Agelaius phoeniceus)

“…Many species improve signal detectability by increasing the minimum frequency of their songs, which, because of the low-frequency nature of anthropogenic noise, can reduce masking effects (e.g. Bermúdez-Cuamatzin et al, 2009;Kirschel et al, 2009;Ripmeester et al, 2010;Verzijden et al, 2010). In our study, the minimum frequency of trills did not differ between treatments, perhaps because the frequency range of red-winged blackbird trills (2.75-5.0kHz) exceeded the frequencies contained in our experimental low-frequency white noise (0-1.83kHz) and exceeded the majority of frequencies produced by traffic (again, traffic noise is concentrated below 3kHz) (Cornillon and Keane, 1977;Halfwerk et al, 2010;Wood and Yezerinac, 2006).…”

“…Finally, some species increase signal detectability in noisy environments by producing an alternative type of signal with better transmission properties (e.g. Bermúdez-Cuamatzin et al, 2009;Dunlop et al, 2010). Red-winged blackbirds have only a single song type, however, so this strategy is not an option for this species.…”

Immediate spectral flexibility in singing chiffchaffs during experimental exposure to highway noise

“…The latter result in particular is novel in methodology and conceptual implications, as it strongly suggests the general ability to rapidly respond to fluctuating noise conditions. Although the underlying causal mechanism may vary, such an immediate spectral shift may also explain correlative patterns in other studies on other species (Slabbekoorn and Ripmeester, 2008;Bermudez-Cuamatzin et al, 2009;Parris and Schneider, 2009;Ripmeester et al, 2010). Without experimental data we are currently unable to ascribe those correlative patterns in other species to an evolutionary, ontogenetic or immediate adjustment of singing (Patricelli and Blickley, 2006) (but see Halfwerk and Slabbekoorn, Singing flexibility and highway noise 2009).…”