Preen gland occurs in

If a bird is transferred from $30^oC$ to $10^oC$,its body temperature will change to:

"Telescopic vision" is found in .........

Identify the correct statements regarding class $Aves$.
$I$. Forelimbs are modified into wings and hindlimbs are modified for walking and swimming.
$II$. Heart is completely four-chambered.
$III$. They are homeotherms.
$IV$. They are oviparous and development is direct.

The skull of a bird is

Flightless birds belong to: