The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Snails, fish, insects, weather, meteorites, climate, birds and/or flowers. All are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located.
April 2013
Pacific Northwest
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Cormorants are black. And blackbirds are black, right? Well, not exactly, especially if you are lucky enough to see them close by, in the sun.
April 26
Freshwater wetland
I stopped by a wetland nearby and saw this lone Brewer's Blackbird (Euphagus cyanocephalus) standing on a fencepost. Usually I see them in big flocks, plain dull black, perched on a power line, or scavenging in fields. But this is breeding season, and this fellow was the only one around that I could see. He sang quietly, a light squee, and preened, showing off his shiny plumage of iridescent green, blue and purple.
Then he puffed himself up, fluttering his colorful plumage. A mating display for sure. I did not see a female but I kept walking. Mr. Blackbird's display was not for me!
April 30
Anacortes Ferry Dock
This afternoon the pilings and wingwalls were crowded and busy with Pelagic Cormorants (Phalacrocorax pelagicus). These are the smallest of the cormorants we have in the Northwest, and, in spite of their oceanic name, prefer nearshore waters, diving after small fish and crustaceans in shallow water. The books say they are less sociable than our other cormorants, but that's not the case with this group. There are at least 30 or so I can see in one view, some perched on the structures that guide the ferries in, or flying around in the vicinity. They used to nest in the wing walls too, on the steel and wood open shelves that are like seabird condos, but the Department of Transportation put a stop to that, stringing wire to block their access. Not sure why, probably some safety issue. Even so, the birds are thick up there, preening, oblivious to the big boats coming in and out all day long with cars and people within a few feet.
In the sun, their glossy purply-blue necks and green backs dress up the usual silhouette-like black plumage. These colors are not due to pigments, any more than the blackbird's are. This is
iridescence, or "
structural color", caused by light bouncing off feathers that have a multi-layer structure. Light is composed of a range of rainbow colors, that looks white when we are seeing all the wavelengths at once, but breaks into colors when the wavelengths arrive at our eyes separately, each wavelength being perceived as a particular color. Feathers, and quite a few other materials, have microscopic structural complexity that refracts and reflects light, reinforcing some wavelengths and canceling others. The net effect is to appear colorful in certain shades when viewed at a particular angle. An extreme example of this is a hummingbird's throat: brilliant red when viewed face on, and black when seen from the side. We see the light wave interference pattern from cormorants and blackbirds as shades of glossy green to blue.
Since we're in the breeding season, these cormorants have even more colors brightening up their basic black right now too. White patches on their rear, red around their eyes, and white hairlike feathers called filoplumes adorn their necks. Some individuals are more flamboyant than others among these several photographed preening on the wingwall as my ferry pulls away from the dock.
Just because, I'm adding one more bird, my favorite duck, the Bufflehead. Though only partly black, take a look at the iridescence on these males. This is the real color! Aren't they gorgeous!
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Birds in the Bucket today, and colors. What's going on in your neighborhood today? What's colorful? Any and all observations are welcome in the Bucket.