If an observer notices consistently bright red males in the spring, what can they generally infer about the local food supply?

Answer

The local seed offerings are rich in carotenoids

The brightness of the male's red coloration is an indicator of his recent dietary intake; specifically, bright red plumage suggests that the available food sources have been rich in the necessary carotenoid pigments.

If an observer notices consistently bright red males in the spring, what can they generally infer about the local food supply?
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