Mary:
I love raptor discussions but this is a tough one to say for sure. Adult Red-tailed Hawks can look like they have dark flight feathers sometimes (I read it one of the guide books), and the mention of black wingtips doesn't fit for Swainson's Hawk and fits better for Red-tailed Hawk. But who knows, it can be tough to say what a bird is for sure, but always great to discuss them. I have seen two Swainson's Hawks in Western WA over the years and both were high flying birds going north on a spring migration -- I'm guessing?