I'm not sure I'd say clutter. The colour of the background both repeats the colour of the bird but also disguises it. The background does distract from the bird which looks very sharp to me.
This would be a killer background had you had more separation. if you are handy in PS, maybe try and blur it a little bit to avoid distracting from the beautiful bird.
Welcome, Bill! This must have been one of the few days of the year when the plumage of the cardinal works as perfect camouflage. :) I like the alert pose but find the bird a bit too centered.
Welcome, Bill! This is a nice image, your subject is sharp and well exposed. I agree with some of the previous comments. Taking the bird out of center and perhaps working a little PhotoShop magic to blur out your background would add a lot to this image. Keep 'em coming!
Too much clutter if it's a portrait of a bird. Not too much clutter if it's a portrait of a bird and an environment, IMO. If it's too much clutter to suit you, then a lasso of the bird in PS, inverting it and then applying gaussian blur to taste will separate the cardinal from the BG.