How does the European Goldfinch diet specialization manifest regarding beak length?

Answer

The male possesses a longer beak than the female to extract seeds from teasels

Due to their highly specialized seed diet, the European Goldfinch male has evolved a longer beak compared to the female, enabling him to extract seeds from teasels that the female struggles with.

How does the European Goldfinch diet specialization manifest regarding beak length?
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