Go ahead and place your cut Christmas tree outdoors either in it's stand or in a pot full of sand and rock. Then re-decorate the tree with lots of bird treats such as orange halves, pine cones covered in peanut butter and bird seed, or even small bird feeders. The tree adds for protection and a great food source for so many birds.
You can also cut up your Christmas tree and lay the branches over your roses, tender perennials, or any plant to help protect and insulate against a harsh winter. I find that these branches also help provide protection and shelter for critters.