Yellow-crowned Night Herons are spotted regularly during migration in southern Wisconsin, and may even breed rarely in the state, with a few reports in the Wisconsin Breeding Bird Atlas.
Cuckoos are secretive, so spotting them and making an identification only by their bill color is difficult. Both can be found in the same habitats which adds some complication to ID, but there are a couple other good ways to tell them apart.
A stout songbird that commands attention with its striking appearance, the Eastern Kingbird sports a black head, back, and tail, contrasted by a crisp white underbelly and a distinct white band on the tail.