It looks fairly simple to construct. I would assemble the body out of PVC and use a fake pumpking for the head (can usually be picked up at michaels during the fall but are a tad $$$) A few black sheets and some old dry sticks. THat would be the quickest and easiest way to construct it. But if you are looking to imitate the one from the movie to a T. Then It will take some more time and few extra supplies (wire, tape, paper mache, airbrush). Tim Burton has the amazing ability to create some really great scarecrows.
I just noticed that nyhaunter has Vicious Dog Wrangler under their name, but then has a picture of the cutest little dog I have ever seen as the avie!!! That is just cracking me up I love that Just wanted to say that!