First off I would say feed you hawk a healthy balanced diet and don't waste your money on supplements. Next, before you head out trapping, make sure you know where your closest avian vet is located. Then as yosemity suggested, get some mite and lice spray. A good number of wild red tails your going catch are going to have flat flies. I've been doing this over 30 years and it still makes my skin crawl when I catch a bird and see the flat flies. Other than that, most of the things you would use for first aid on you bird you are likely to already have in the house.