This is a note from the guy who lives on Sycamore Island.

Speaking of nesting pairs, I saw the two peregrine falcons that are 
likely nesting under the beltway bridge. On Friday afternoon I went 
over to Turkey Run Park, (I had to drive there instead of my usual 
canoe route), to take a hike and look for any ice climbing 
possibilities. The trail was sheer ice when I got there, smooth and 
untrampled, but luckily I came prepared. I put on my crampons and 
grabbed my ski poles and trudged the two miles through the snow to the 
beltway. Then something in the sky at the head of Plummers Island 
caught my eye. I knew immediately that it was some kind of bird-of-prey 
when I saw the flap-flap-flap-soar flight pattern, but when it banked 
at mid-river and showed me its long pointed wings and slate grey color 
I knew it was one of the perigrines that I had heard about. I watched 
until the bird came to rest on a tree limb on Plummer's, very close to 
and level with the bridge. Then I saw the mate perched on a limb 
nearby.