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Posted by Alex on 19:27:50 07/19/04
In Reply to: Come on now... posted by Steve Pagliughi
Okay, okay, I'm coming out of hiding ;)
I'll give my two cents
I was waiting for a response myself since I don't have any experience with any juvenile cuckoo of any sort. However, I did find in Sibley's a "head shot" of a juvenile Yellow-billed Cuckoo. First off, the Yellow-billed Cuckoo young juvenile is very pale, about as pale as a Black-billed, aka your knee-jerk bird. I am not sure how pale a juvenile Mangrove Cuckoo is, but I would imagine a darker brown than the juvenile Yellow-billed. I will also guess that some really young Mangrove juveniles might lack the dark mask. Most importantly, I don't think the young Yellow-billed would display that much rufous.
So, bottom line is, it would be really helpful for a field guide to at least mention the differences of a juvenile in flight to an adult, but they are not going to make it that easy.
Both young Mangrove and Yellow-billed Cuckoos would be paler than their parents, Mangrove might lack the mask when it first fledges, and the Yellow-billed juveniles might lack the rufous under the wing. However, the belly color could be something that does not change from the moment the bird fledges to adulthood. The Mangrove Cuckoo juvenile SHOULD (I'm not saying a Yellow-billed juvenile could have a buffy color on the breast from when in the nest, like a downy feather) have a brown or buffy brest, while I suspect the Yellow-billed juvenile would have a white belly. I'm sorry I could not have any info on a juvenile in many terms. So I guess, unless you can find a good resource, it all comes down to the color of the belly.
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