Comment by mime454 on 20/04/2022 at 00:04 UTC*

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View submission: The long-held theory, first suspected by Darwin and Humboldt, that tropical birds at the equator are more colourful than non-tropical birds has been proven analyzing 24,000 photos of birds. The new study suggests dietary differences, as well as the influence of their habitat, could play a key role

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This actually is one of those cases where the exception proves the rule.

The male cardinals are red because the ability to generate red plumage in winter suggests good nutritional status during the pre-breeding season and the ability to avoid predators while being conspicuous (resulting in young that likely have those traits as well). The red signal is honest specifically because it is hard to maintain.

There’s another line of explanation that states the male cardinals are red in the winter because it activates the female nervous system with a powerful sensory stimulus. These explanations don’t have to contradict. They probably just each tell us something different about how this trait was originally evolved and maintained.

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There's nothing here!