Northern waterthrush
At Dr. Aborn's study site in Tennessee, it was very busy. The most numerous birds around were Northern waterthrushes, the first ones he'd seen this spring. They are known for bobbing the rear half of their body as they walk. Watch and listen for them now during migration where you might spot them on the the ground or wading in shallow water, feeding on insects, snails, arthropods, and sometimes small fish.

Dr. David Aborn