Saturday, October 6, 2012

Bald heads reveal dinosaur ancestry

I took the feeders down this past spring to keep the bears away and instead have been scattering black oil sunflower seeds on the broad railing and picnic table on our porch. In the summer I was doing it at dawn, but now, with the shorter days, it's closer to 6. As soon as I step out on the porch I hear the Chickadees calling to each other, announcing that breakfast has arrived. They are landing even before I am finished. In a nearby tree I hear the resident Cardinal alerting his mate. They are a little bit more cautious and wait until after I have gone back inside.

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

17 comments:

  1. Look at the eye of a Pileated Woodpecker. I realize this is not scientific, but tell me you don't see the v-raptors in Jurassic Park.

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  3. how lovely to have the birds right near to your back door (shame about the bears though). You shared some lovely photographs of another phase in their lives; they're still beautiful

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  4. Interesting stuff, Hilke! I agree, they do look like dinosaurs, but pretty pitiful in this state I think!

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  5. I really enjoyed this post, Hilke!

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  6. Very interesting post filled with great photographs of Blue Jays in their molting stage. Quite a sight those bald jays are! They really do look rather dinosaur-like!

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  7. Interesting info Hilke! The poor jays don't look so good in this state

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  8. Poor little thing. Looking very sorry for himself.

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  9. I posted one last year. They are so incredible looking. Great shots. Boom & Gary of the Vermilon River, Canada.

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  10. They sure do look different without their feathers!

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  11. I feel sorry for the birds with their naked heads. The jay looks almost sickly!

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  12. Our Blue Jays are finally back in full feathers. They can really look motley for a while!

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  13. Great photos and very interesting to see birds moulting like that.

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  14. They do look reptilian without those lovely feathers.

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  15. Poor guys were not ready for picture day;')~

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  16. Hi there - great pictures of a less than great looking birds. The evolution of birds is such an interesting topic.

    Thanks for linking to WBW

    Stewart M - Australia

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  17. Beautiful colour on the birds.

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