Biology Reference
In-Depth Information
uropygial gland (also preen gland).
A gland found at the base of the tail that produces
drops of oil used by birds to keep their feathers in good condition.
vanes.
The webbed sides of the feather.
Wulst.
The area ofthe brain that processes information frombotheyes toprovide stereo-
scopic vision.
Zugunruhe.
Migratory restlessness in response to changing day length and/or the chan-
ging angle of the sun in the sky. Virtually all migratory species experience this urge, in-
cluding individuals that have been hatched and reared in captivity.