Their back. I thought I was hearing Seagull's. Which we don't really get around here. Then I found out it was two red tailed hawks circling. I've seen one before. But, it didn't make any noise. Must be a couple now communicating as they soar.

EDIT: I notice today the sounds come from the same location all the time. The hawks circle around it. I think they must have nested ~400yards from us and what I'm hearing is their chicks.