I finally got a chance to go up to Columbia University to see what was happening with the Havemeyer Hall nest. When I arrived a hawk was sitting on the nest. After about fifteen minutes, a hawk with a brown tail arrived and landed in a tree near the nest. The hawks did an exchange, and the young hawk sat on the nest.

There were reports of an injured hawk being picked up from the campus a few weeks ago, and I suspect this young hawk took advantage of this opening to quickly mate with the established female.