They like my feeder, and though they vanish from late autumn to midwinter, right around January they always return, and kick around for awhile, snagging suet and flaunting grumpy little bluebird butts from the railing. For a considerable chunk of the year, I see them daily.
Despite all this, on a sunny day, the blazing denim blue of a male bluebird's back can still stop me in my tracks.
I think it's because it's blue. Blue is hard-wired somehow. Cardinals are just as intensely colored, often moreso, but while I enjoy them, and will stop to admire a vivid male, the color doesn't go straight to the back of the brain the way the blue does. I know there are no natural blue foods (NO, BLUEBIRDS DO NOT COUNT AS A BLUE FOOD!) and I wonder if, like black and yellow being the most eye-catching color to humans, there's something about blue, if the fact that we eat nothing blue has been etched in our mental circuitry, and seeing it, even on a bird, sends chemicals screaming through the brain going "Look! Pay attention! This is important! Look at this carefully!" Maybe the bluebird's aesthetics are somehow benefiting from the desire of ancient primates to avoid tainted meat. I don't know, probably a stretch.
On the other hand, I have no desire to stick a bluebird in my mouth, so hell, maybe it works.