I sit corrected! 
.5% of a red-tail's diet can be fish.
Diet: mammals including mice, rats, moles, shrews, squirrels, pocket gophers, cottontails, opossums, muskrats, weasels, how cats (70-85%); birds including ducks, coots, pigeons, quail, rails, gallinules, doves, woodpeckers, songbirds, pheasants, crows and rarely poultry (10-15%); reptiles and amphibians (3-10%); fish (.5%); invertebrates (1-5%)
I have a pair of red-tails that nest in an old oak here on the property and raise their young here every year. One of the fledglings got off to a hard start this season and I had to bring it in to play catch up with the others. S/he had no attraction to fish at all, but man, you should have seen its eyes pop when I offered a mouse! They've never attacked my chickens or cats in the years they've lived, bred and hunted here, but they do a great job on the furry vermin the kitties miss!
Marie
