What specific feathers on the adult Whooping Crane are typically black, contrasting with its snowy white plumage?

The primary flight feathers at the wing tips

While the body plumage of the adult Whooping Crane is predominantly snowy white, crucial identification markers exist on the extremities. Specifically, the primary flight feathers, which are the largest feathers located at the outer tips of the wings, are black. This black coloration is highly visible when the bird is in flight, serving as a key field identifier against the stark white body. However, when the crane is stationary on the ground with its wings folded, these black tips can sometimes be concealed, potentially complicating identification if other markers are obscured. The alula, a specialized set of feathers on the leading edge of the wing, can also be black or grayish, but the most consistent and defining black markings associated with its standard plumage are those on the wing tips.