What physical feature of the Rose-breasted Grosbeak heavily influences the required feeder design?
Answer
Noticeably large, thick, conical bill
The bird possesses a noticeably large, thick, conical bill, which is a robust feature suggesting it is built for cracking hard shells, thereby influencing the need for feeders that can accommodate this physical characteristic.

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How to attract Rose-breasted Grosbeaks - Basic tips - YouTube
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