Preen glands occur on

Which of the following characteristics is applicable to birds $(Aves)$?

Students of class $XII$ were given a list of the following characters: clawed toes,curved beak,feathers,pneumatic bones,wings,and fur. In this list,how many are volant adaptations?

Which of the following is $NOT$ found in birds?

Pneumatic bones are found in

In birds,the urinary bladder is ..........