The Costa's is one of our most spectacular hummingbirds down here in southern Arizona. The problem is, it's practically impossible to photograph in such a way as to show it. Right now (in mid winter creeping towards spring), the male is in its brightest plumage. Here is an example of a photograph of a prime male. It's a perfectly nice bird, but that is all you can say about it. The top of the head, and the throat are dark, but sort of purplish underneath. But if this were the real bird in the flesh that you were looking at, here is the experience you would have: First the bird would appear more or less black on the throat and crown, then it would glance towards you and the color would suddenly flash up brilliantly. Then it would turn away, and the color would dull down again.
Now, I think two things are operating. First of all, the bright colors on a hummingbird's throat are not real colors (not, in other words, created by a pigment). They are created by narrow microscopic ridges which from a certain angle split up their basic colors into a prism as oil does when its individual colors break up in water or ice crystals in a rainbow. When you are looking at the bird's feathers from just the right angle they shine, from any other angle they are likely to show up as black.
Now if it sounded like I didn't know what I was talking about there, I really don't understand this second part. Someone recently explained to me why, when you take a photograph of a rainbow, or a brilliant fiery sunset, it comes out so disappointing, with all the color washed out of it. Well, that's another reason it's hard to get a picture of a Costa's that does it any justice, and apparently you can do something or other to overcome the failing, or maybe it takes a special kind of lens, but I don't remember.
But I've taken so many picture's of Costa's Hummingbirds that some of them have got a little color into them. Much of the color on them is on phalanges that stick way out on either cheek, and the rest on the throat and crown.
The first picture here shows some color, the next one from nearly the same position, show the color reduced to black. Note the famous "ear flaps" on these.
And here is the female Costa's, pretty in her own way
