Its no more usual than for any other endangered species - the peregrines may be fast like cheetahs but their numbers and therefore their genetics aren't that bad. There is some research being done on genetic bottlenecks in peregrines but haven't heard of anything published yet.
As for Ivy, I think Ivy wants a territory and the women are getting there first. Lucy then Princess. It was Lucy's first attempt at nesting and then she was gone, was it because she died, or did she realize that she could potentially have more and more robust offspring with an unrelated male. Who knows. Princess has only ever mated with Trey but its possible that she could go through a couple of mates if she avoids an accidental death. In 2008 she actively avoided Ivy. From what I've seen on the cam, she doesn't seem any more enamoured of him this year ... but if Trey doesn't return and no other, likeley candidates come around, she might take him up on the offer. It really is just wait and see what happens I'm afraid!!
