Question

Which of the following characteristics is found in all birds including flightless birds?
A) Well developed wings for flying
B) Presence of feathers on the body
C) Only right ovary
D) Syrinx and oil glands at the base of the tail.

Answer 1

Hint: It is key to note that the shape and size of the breast will be greatly different between flightless birds and those that are fabulous flyers. The streamlining also differs depending on the flight range of the species.

Complete answer:
All species of birds do have wings, whether or not they can fly. This includes the flipper-like wings of penguins. However, flightless birds have greatly underdeveloped flight muscles – chest and pectoral – and they lack the carina which is needed to anchor these muscles in place. Option A is incorrect.

The correct answer is option B. All birds have feathers on their bodies. These include flight feathers, decorative plumage, tiny feathers which are insulating like the penguins, plumage like the ostrich, spiky feathers of the kiwi, and so on.

Female birds do have only one ovary, but this is the left ovary, not the right. Thus option C is incorrect.

Most species of bird do have the oil or preen glands at the base of the tail, but it is missing in some like the members of the dove family. Option D is not correct.
Though the preen gland is missing in birds like the ostrich and kiwi (flightless land birds), it is greatly developed in aquatic species including the osprey and pelicans.

Hence the correct answer is OPTION(C)

Note: The use of the oil glands differs from species to species of birds. They could be used to maintain the bill, keep feathers waterproof, and also be a precursor to vitamin D, which after preening is absorbed by the skin.