17", hmmm...that's probably almost 2x as long as a Shrike (i'm assuming 17" is the length & 30" is the wingspan - not sure the proportions are right, or did you mean it was b/t 17" and 30" in length, or is that the wingspan? i'm quite confused now). So, it can't be a Shrike if it was that long, but it sure looks like one. Normally, kites have deep set eyes with a ridge over them. Sometimes the recessed areas around the eyes and under the ridge can appear darker, either from shadows or from an actual darker coloration. Occasionally, the head can be a bit grayish on the top and back instead of all pure white. Still, even taking all this into consideration, i first felt that it was a Loggerhead Shrike (it looks so much like one), but now with the size as you stated, it simply can't be one. I think that 17" might be just a bit long for even a White-tailed Kite, but i'm not sure since it has been so long since i studied birds.
Did you see it hover in flight, looking down trying to spot prey or home in on moving prey that it spotted? Kites can do this when they're hunting. I don't remember the wing markings that might help identify it as a Kite. Oh,...did it soar with its wings in a dihedral (similar to a Turkey Vulture's soaring)? White-tailed Kites can soar in this fashion.
Let me think on this. Where was the pic taken?