Urban European blackbirds (Turdus merula) have been observed singing at higher minimum frequencies and with shorter inter-song intervals than their rural counterparts. Researchers attribute the shift in pitch primarily to the necessity of overcoming low-frequency anthropogenic background noise, such as traffic rumble, which would otherwise mask lower-pitched vocalizations. Additionally, urban blackbirds frequently sing during nocturnal hours when ambient noise levels drop, a behavior rarely documented in rural populations where artificial nocturnal illumination is absent.
Based on the passage, which of the following statements regarding European blackbirds are supported by the text? Select all that apply.
- Urban blackbirds adjust their vocal pitch at least in part to prevent their songs from being masked by human-generated noise.Cevap
- Nocturnal vocalization occurs with greater frequency among urban blackbird populations than among rural ones.Cevap
- CUrban blackbirds have developed anatomical modifications to their vocal tracts to produce higher acoustic pitches.
- DRural blackbirds completely cease all acoustic communication whenever exposed to human-generated noise.
- EArtificial light pollution is the primary driver causing urban blackbirds to raise the pitch of their daytime songs.
Cevap
The statements indicating that urban blackbirds alter vocal pitch to prevent masking by anthropogenic noise and that nocturnal singing occurs more frequently in urban populations than rural ones are supported by the text.
The passage directly supports two factual inferences: first, that urban blackbirds alter their song pitch to prevent vocalizations from being obscured by low-frequency anthropogenic sounds; second, that singing at night is documented far more regularly among urban populations than rural ones.
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Drawing valid, directly supported inferences from comparative textual details
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