To build on the previous suggestions, I would suggest that baseball caps in black for the crow, and brown for the fox would be a great starting point. If they are not available in those colours, you can certainly paint the caps with acrylic paints. (Very inexpensive and quick drying.) A black cap for the crow could have the bill painted yellow to represent the bill of the bird, and the fox's cap could be all brown-red with a pink or black triangle nose on the very tip. You could dress the crow in black sweatshirt and pants. On the arm of the black sweatshirt you could glue, (with hot glue, I'm thinking) some black feathers, just a few, along the top of the arm. I would take some thick black felt, draw a tail, and glue some black feathers to that and attach it to the black sweatpants with a large pin. (So as to leave the sweatpants viable.) The fox could wear brown and you could freehand a fox's tail from felt, being the least expensive material and overlay a white tip of felt on the end. This can be glued too something stiffer, as in the material that makes hat brims stiff, or you can just use a couple of layers of felt. Again, I would pin the tail to the bottom, but in the case of the fox you may wish to pin his tail up at least halfway with another pin. Children seem to really be amused by having an animal tail, it seems to really put them in the little animal mood. (LOL, I can't tell you how many Pikachu costumes my children have asked me to make them, and that's a tough one.) I hope that helps in some small way. Sorry this is so long, but I love making costumes. I made my dear friend in Carolina a Queen Amidala costume, and she actually won a prize.
Take care,
miraged,