Do you know Mark Herrera?
As of an hour before, I did not know.
He sent an email to me about zeably.com which is actually big database of images that we all can use.
I tested it by searching for some of my favorite birds by name and I got them all right. I am sure not many bird lovers are aware of them.
Mark's email said, " Zeably is one of the largest image galleries on the world wide web with
unique access to greatest collection of images. With archives holding
millions of images, our aim is to make this incomparable collection
accessible to all. You can find images for millions of topics".
Unlike Google images, there is no choice image sizes here. You have to use whatever is shown to you.