English — Language and Literature (184) — CBSE Class 10 board question

Each year, thousands of birds migrate southwards to avoid the harsh winter, embarking on an incredible journey that spans thousands of miles.

• Migrate means to move from one region to another seasonally — used for birds, animals, and fish. It is the correct word here as birds travel southwards and return, implying seasonal, cyclical movement.
• Immigrate = to come into a new country to settle permanently (used for people/animals entering a place).
• Emigrate = to leave one's own country permanently (also used for people).
• Neither "immigrate" nor "emigrate" fits birds' seasonal, round-trip journeys. The textbook activity also lists "Migratory Birds — Tracing Their Flights" as a topic, confirming "migrate/migratory" is the standard term used in this context.