In the city of Pittsburgh there’s a delta where waterfowl gather all year.
Nine Mile Run empties into the Monongahela at Duck Hollow to form a mud bar and shallows that attract a permanent collection of dabbling ducks. In the summer the flock is mostly mallards. In the winter gulls join the crowd. During migration anything can show up.
Last Sunday the river was running high when I stopped by to see who was new. As usual the flock was dominated by dabblers — all of them mallards — but there were three birds who didn’t fit in. All of them dive underwater to catch fish and crustaceans: a pied-billed grebe, a hooded merganser (I thought it was female. I hear it’s an immature male), and a common merganser (female).
The common merganser has been there for months. Birders have noticed she can’t fly but she can fish and has found safety in the mallard flock.
When the other two birds arrived the three formed a trio that cues on each other for feeding locations. They even hang out together when resting.
They know they have something in common. They’re divers in a dabblers’ world.
(Thanks to Thomas Moeller for the photo and history of this trio.)