One who specialises in the study of birds

A. Biologist

B. Naturalist

C. Zoologist

D. Ornithologist

Answer: Option D

Solution(By Examveda Team)

One word substitute is Ornithologist.

Biologist: an expert in or student of the branch of science concerning living organisms.
Naturalist: an expert in or student of natural history.
Zoologist: an expert in or student of the behaviour, physiology, classification, and distribution of animals.
Ornithologist: a person who studies or is an expert on birds.