A flagship species found in Nagaland, also the state bird, is the:

The correct answer is: a) Blyth’s Tragopan.

Blyth’s Tragopan is a large pheasant found in the eastern Himalayas. It is the state bird of Nagaland, India. The male is a colorful bird with a blue head, red breast, and green back. The female is brown with a white belly. Blyth’s Tragopan is a shy and elusive bird that lives in forests. It is threatened by habitat loss and hunting.

The other options are incorrect because:

• The White-winged Wood Duck is a duck found in Southeast Asia. It is not found in Nagaland.
• The Hoolock Gibbon is a gibbon found in the eastern Himalayas. It is not the state bird of Nagaland.
• The Golden Langur is a langur found in Southeast Asia. It is not found in Nagaland.