Gouldian Finch chicks are born with phosphorescent beads around their mouths which glow in the dark. This helps their parent’s to feed them in the pitch black.
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No, not just for feeding in the dark, but also a defense against
Brood parasites
One of my favorite evolutionary developments! Other species of birds will lay eggs in finch nests, leaving the finches to do extra work raising their young.
This has led to an evolutionary arms race, which has led to extreme gape coloration.
Among the most successful brood parasites is the cowbird. Like most brood parasites, the cowbird chick is larger, has a larger gape and is more likely to get more food than it’s nestmates.
But as you can see, the gape of the cowbird is a slightly different color than the other chicks’. It has a red gap and white rictal flanges.
This difference spurs the evolutionary pressure for parents to see color and fine patterns, so they can select for their chicks when feeding.
Not to be outdone, brood parasites then felt the selective pressure to more closely mimick the nestlings, and the race was ON.
We have such stunning likenesses as the pin-tailed wydah (parasite, left) and the common waxbill (right).
Gouldian finches are among the champions. (The adults are quite stunning, btw)
These guys are parasitized by cuckoos, also champions in the game.
Gouldian finches are cavity dwellers, so their chicks hang out in the dark most of the time.
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