High levels of environmental noise erode pair preferences in zebra finches: implications for noise pollution

Male–female pair bonds are common to most bird species, and these bonds affect fundamental aspects of mating systems and the strength of selection, for example, by limiting extrapair paternity. Therefore, understanding factors that strengthen and erode pair bonds are important in elucidating the selection pressures that avian populations will experience. Here, we studied the effects of environmental noise on pair bonds and the strength of pair preferences (i.e. preferences for a pair-bonded partner versus an unfamiliar individual) in the monogamous zebra finch, Taeniopygia guttata, a model species in studies of sexual selection. Based on a previous study, we hypothesized that high-amplitude environmental noise would decrease the strength of pair preferences. Explicitly, we tested whether females' relative preference for their pair-bonded males, compared with extrapair males, decreased as the amplitude of environmental white noise increased. Our results generally supported our hypothesis, as females' preference for their pair-bonded males significantly decreased under conditions of high environmental noise. This erosion of preference may result from the masking or distortion of the paired males' pair-bond maintaining call, although the decrease in preference could also occur because a female cannot recognize her pair-bonded male. Our findings suggest that songbird populations in areas with high environmental noise may have (temporarily or permanently) weakened pair bonds, suggesting that extrapair behaviours could increase in areas of greater environmental noise.