Recent bioacoustic studies of urban house finches (*Haemorhous mexicanus*) observe that males in noise-polluted city centers sing at significantly higher minimum frequencies than their rural counterparts. Ecologists hypothesize that urban finches elevated their vocal pitch to avoid acoustic masking by low-frequency traffic rumble, thereby maintaining effective mate communication. To test whether finches dynamically adjust pitch in response to ambient sound levels, researchers recorded urban finches before and during a temporary two-day highway closure. Despite a dramatic reduction in low-frequency background noise during the closure, urban finches continued singing at elevated frequencies. Defenders of the acoustic masking hypothesis maintain that this result does not disprove the hypothesis, suggesting that pitch elevation may reflect permanent structural adaptations or early developmental learning rather than real-time vocal modulation.
Consider each of the choices separately and select all that apply.
Which of the following, if true, would provide additional support for the defenders' explanation of the highway closure results?
- Finch nestlings exposed to played-back traffic noise during early developmental learning windows permanently adopt higher minimum song frequencies, regardless of ambient noise levels in adulthood.Answer
- BUrban finches singing at higher minimum frequencies attract fewer potential mates than rural finches singing at lower minimum frequencies.
- Anatomical examinations reveal that adult urban finches exhibit syringeal muscle modifications that physically constrain their ability to produce lower-frequency vocalizations.Answer