Thanks to great detective work by Nina Wolf and other birders in Riverside Park, the new nest site of the Riverside Hawks has been discovered. I was able to confirm the nest location on Saturday, but wasn't able to see the hawks in the nest until Sunday morning.
The nest is on a traffic island at the next exit north from their old nest. It is on a strip, that due to heavy traffic, is cut off to humans, dogs and raccoons. Best of all, there are a row of benches for any and all hawk watchers to sit on!
Update: March 22nd. The Hawks ended up choosing a nest site a few blocks north of the Boat House Café. This is not unusual. Hawks may build an alternate nest, and then not use it.