December 20, 2008
Blue Christmas
It has been snowing all day. We have at least 6 inches of snow on the ground. Astoria does not usually get this much snow all at once, and it is equally unusual to have a week's worth of the stuff. This is shaping up as an unusual winter. The long-term forecast for the remainder of the week depends, in part, on which service one chooses to believe. The National Weather Service is calling for snow on and off through Christmas Day. The Weather Channel folks are somewhat more optimistic, calling for rain on the coast and a "wintery mix" inland...
At any rate, my day has been spent watching the birds coming to the back yard. Michelle and I even built a new bird feeder. I've also been taking a few photographs through the kitchen window (which could use a good cleaning).
Which brings me to "blue" birds. Most blue colored bird appear so because of how white light is refracted through the feathers. The structure of the feathers causes the color, so the colors produced are call structural colors. If you watch jays and bluebirds, you'll notice that the deepness of the blue changes depending on the relationship between the bird, the light source and the observer. Sometimes a Steller's Jay seems almost black, other times very blue.
The blue of a Scrub Jay is different than the blue of a Steller's Jay because of a difference in colors produced by pigments, rather than structure. The principle pigments in jays are melanins which produce, blacks, grays and browns. Steller's Jay feathers have more melanins in them, so they appear darker blue.
On a day with good light Varied Thrushes will show a structural bluish sheen to their back feathers. The orange color is produced by a different class of pigments called carotinoids. These pigments produce red, yellow and orange colors.
Which also explains flickers...
Posted by mbalame at December 20, 2008 3:15 PM