Q. Which of the following is not a bird? (UPSC Prelims 2022)
Answer: Golden Mahseer
Notes: The correct answer is [A] Golden Mahseer. This question tests your ability to distinguish between different taxa of Indian wildlife.

• Golden Mahseer (Statement A – Correct): The Golden Mahseer (Tor putitiora) is a large, iconic species of fish found in the Himalayan rivers. Known as the "Tiger of the Indian Rivers," it is an endangered species highly prized by anglers. It is the State Fish of several Indian states, including Uttarakhand and Arunachal Pradesh.
• Indian Nightjar (Statement B – Incorrect): The Indian Nightjar (Caprimulgus asiaticus) is a small, nocturnal bird known for its camouflaged plumage and distinctive "churring" call. It is commonly found across the Indian subcontinent in open scrub and forest edges.
• Spoonbill (Statement C – Incorrect): The Eurasian Spoonbill (Platalea leucorodia) is a large wading bird. It is easily identified by its long, flat, spatula-shaped bill, which it swings through shallow water to catch small fish and crustaceans.
• White Ibis (Statement D – Incorrect): The Black-headed Ibis (often referred to as the Oriental White Ibis) is a large water bird with a white body and a prominent, down-curved black beak. It is a common sight in Indian wetlands and marshes.

While all four are part of India's rich biodiversity, the Golden Mahseer belongs to the class Actinopterygii (ray-finned fishes), whereas the others belong to the class Aves (birds).