Who's the Hawk?

I have recently been paid a pair of puzzling visits by an as-yet-unknown hawk. He looks like he could be either a sharp shinned or a Cooper's hawk, but the two are so similar that identification is gravely challenging (see this lovely comparison by Project Feederwatch). At first glance he bears characteristics similar to both hawks, and it's maddening trying to ascertain which he really is. The only positive characteristic I can note is age; he has lighter colored, nearly yellow eyes, which according to CapeCodAlan of ebirdseed.com, indicates the bird is a juvenile.

His behavior also indicates inexperience. Twice in the past two weeks he has arrived with great fanfare at our backyard feeders, but neither time has he been successful in securing a meal. The first time he landed near the hopper feeder and waited there for a minute or two, stretching his wings and looking about as if wondering where the buffet had disappeared to. The second time, just this past weekend, I went to our patio doors to look out at the yard and he was perched on the platform feeder we keep just a few inches from the house. He stayed there for a period, eyeing me with caution but not concern.

Unfortunately, I have no superb pictures by which to determine a clear identification. I am wondering if indeed this is the same bird -- I believe so, but the first to visit may have been larger. CapeCodAlan believes he may be a sharp shinned hawk, and any fellow birders who have leads as to his identity are welcome to chime in; I'd love to know for certain who is preying in the backyard.

Which brings up the question of welcome. To some backyard birders, these birds of prey are most unwelcome -- our neighbors would prefer to chase him away when he frightens the smaller species. To me, however, it is a rare treat and privilege to have this unusual visitor grace my yard. And if, in doing so, smaller birds fall victim to his dives, then that too is a type of backyard birdfeeding. Perhaps not what I'd intended when refilling the seed feeders, but it is all part of the migration of life I'm happy to be a part of.