The minutes of peaceful feeding usually end with the noisy arrival of a family of Blue Jays. They are molting in late August and every year one or two sorry-looking individuals show up bald - with few feathers, or may be just a stubble on their heads. Fortunately that's only a temporary state lasting about two weeks until the feathers have regrown.
Although adult, they often look immature because their large eyes are more characteristic of chicks:
Others have more reptilian features:
The naked heads remind us that their ancestors are dinosaurs, not mammals, and that their closest living relatives are the crocodiles. They usually reach maturity within 12 weeks, but retain the large eyes characteristics of juvenile dinosaurs.
In a study published in the journal Nature on 5/27/12 examining this curious fact the authors conclude that
"We have provided a powerful new example of how heterochronic changes, paedomorphic" (retaining juvenile characteristics) "and peramorphic" (early development of adult characteristics) "were crucial in the origin and evolution of birds. We further demonstrate that these changes were driven by an extreme degree of elaboration in vision-associated areas of the brain that parallels the olfactory elaboration of mammals, and possibly by the evolution of the face into a precision grasping mechanism as the hands were co-opted for flight."
There is a very readable illustrated summary of the study in ScienceDaily: Evolution of Birds Is Result of a Drastic Change in How Dinosaurs Developed
they do look rather prehistoric. :)ReplyDelete
I'd never thought about their prehistoric characteristic before but you make a good point. Great photos as well.ReplyDelete
These are some great photos.
Great pictures and great information Hilke. We tend to forget the origin of species ;-)ReplyDelete
That's fascinating Hilke. I've never seen that before!! Well doneReplyDelete
there birds need help..ha ha.. great info and photos!ReplyDelete
Wow, you caught one looking at its absolute prehistoric worst! Our Florida Blue Jays have now finished the molt and are once more looking just fine.ReplyDelete
Sad it is, though the pictures are excellent, cheers Hilke.ReplyDelete