In flight, the black centre of the underwing is diagnostic.

They are best distinguished by the pattern of the underwing.

"But through showing the white underwing they made quite a difference.

However, that species has a darker head and all grey underwing.

The underwing is pale and the wing tips are dark.

It flew pretty close to the hotel, giving us a chance to see some underwing which helped with the identification.

When flying, the female has a broad white bar visible on the underwing.

Their wings are long and dark with a distinct white patch on the underwing.

The underwing is white with a dark trailing edge.

It also seems to lack the underwing of gray squirrel tail.

The underwing is largely white with some black spots and brown coloration.

But alas, we illustrated it with a picture of a light crimson underwing.

The underwing is predominantly white with broad, irregular, black margins.

In flight, it shows a green speculum and pale underwing.

The underwing has a black and white pattern which is visible during the undulating flight.

A dark carpal patch on the underwing visible in flight.

Another useful feature is a large whitish panel on the underwing.

The English name derives from the bird's red underwing.

The underwing is chestnut brown and blackish on the edges.

Females are slightly smaller with a yellow stripe on the underwing.

But the underwing glowed like a stained-glass window: deep red, picked out with black.

Perhaps it was just a common yellow underwing.

It is probably under recorded, being very difficult to separate from Copper Underwing.

In flight, the whitish underwing contrasts with the darker body.

When circling overhead, the white underwing of the bird becomes conspicuous.