Ian, Many thanks for your prompt reply and answer to my tweeters
question. Iridescence is a concept that I try to read a textbook
explanation of annually, and one day I hope to be able to explain it to my
grandkids! On this male's head there's no green color at all, and then he
turns it and BINGO! I see it also as our Anna's hummer males suddenly
flash their heads from black to flaming red. They seem to be able to
turn the color on and off, perhaps related to aggression or seeking a
mate. I wonder if the ducks (e.g. Mallards or this wigeon) are able to
use any similar control over their head color.
Fran Wood (male)
Seattle (Madrona)