New answers tagged ornithology
Wild ducklings, like these baby Mallard ducks, are in fact typically only partly yellow: Photo by TheBrockenInaGlory via Wikimedia Commons, used under the CC-By-SA 3.0 license. While I'm no expert, I would guess that the mottled yellow-brown coloring of the juveniles is, at least partially, protective coloration, just like the somewhat similar pattern on ...
It doesn't need to help it survive, evolution has no intent and not all traits are advantageous. It might just be random, genetic drift or something, a bottleneck effect, any of these things. In the wild the yellow ones will hardly live long enough to reproduce though.
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