This is bird node.

On a northern lake,

on a northern lake surrounded by dense evergreens,

a large water bird rests on the surface. Its long slim body, more than two feet of it, appears mostly white. The back black, the head a deep green, and all of it glistens.

The bird dives under a graceful sliding motion,

then returns to the surface with a fish grasped firmly in its beak.

The bird's shape and behavior spell loom.

But this is a male common merganzer, a very large duck that hunts fish for a living.

The common merganzer is one of our biggest ducks, about the size of some lunes, or even a small goose.

Although it's not closely related to lunes, it has evolved a similar overall structure and predatory behavior.

But a merganzer has a unique feature that a loon lacks.

Tooth-like serrations along the edge of the bill that help the bird grasp slippery fish.

Common merganzer's nest in the northern states in Canada. So do lunes. But lunes nest on the ground, while mergansers nest mostly in tree

cavities and rock crevices.

Cavities big enough to house a hefty three and a half pound female,

plus about a dozen jumbo eggs.

For Bird Note, I'm Michael Stein.