Urbanization alters the song propagation of two human-commensal songbird species: Active space, amplitude, and attenuation code

Urban expansion has increased pollution including both physical (e.g.,
exhaust, litter) and sensory (e.g., anthropogenic noise) components. Urban
avian species tend to increase the frequency and/or amplitude of songs to
reduce masking by low frequency noise. Nevertheless, song propagation to
the receiver can also be constrained by the environment. We know
relatively little about how this propagation may be altered across species
that (1) vary in song complexity and (2) inhabit areas along an
urbanization gradient. We investigated differences in song amplitude,
attenuation, and active space, or the maximum distance a receiver can
detect a signal, in two human-commensal species: the house sparrow (Passer
domesticus) and house finch (Haemorhous mexicanus). We described
urbanization both discretely and quantitatively to investigate the habitat
characteristics most responsible for propagation changes. We found mixed
support for our hypothesis of urban-specific degradation of songs. Urban
songs propagated with higher amplitude; however, urban song fidelity was
species-specific and showed lowered active space for urban house finch
songs. Taken together, our results suggest that urban environments may
constrain the propagation of vocal signals in species-specific manners.
Ultimately this has implications for the ability of urban birds to
communicate with potential mates or kin.