It has white primary feathers that form a crescent in flight.

He looked to the metre-long primary feathers at my back.

The wings are long, pointed, and have nine primary feathers.

The plumage is white except for black on its back and in the primary feathers of the wings.

The first couple of their primary feathers are gray.

The quills of the eleven primary feathers appear to be white when seen from above.

The long fingers of the primary feathers can be opened or closed (C).

Members of the family have long, broad wings with 11 primary feathers and about 20 secondaries.

The underparts are white with dark bases to the primary feathers.

The primary feathers range from dark grey to brown.