How Do Birds Know When to Fly South? | Easy Science Reading

This short science reading passage is for English learners. Read the passage, learn key vocabulary, and answer the questions.

Birds use natural signs like daylight, food, and weather to know when to migrate.

Reading Level

A2-B1

Word Count

286 words

Reading Passage

Many birds fly south before winter arrives. But how do they know when it is time to leave? Birds do not use calendars. Instead, they notice natural signs around them and inside their bodies.

One of the most important signs is daylight. As autumn comes, the days become shorter. Birds can sense this change. Shorter days tell many birds that winter is getting closer.

Weather also gives birds information. The air may become cooler, and storms may become more common. These changes can be a signal that it is time to prepare for a long trip.

Food is another important sign. Many birds eat insects, seeds, or berries. When the weather gets colder, insects disappear and food becomes scarce. If birds stay too long, they may not find enough food to survive.

Birds also have instinct. Instinct helps them begin their journey even if they have never migrated before. Some young birds can travel long distances without being taught the route.

Scientists also think birds have an internal clock. This clock helps them respond to seasonal changes. Together, daylight, weather, food, instinct, and internal timing help birds know when to migrate.

Bird migration is one of nature's most amazing events. It shows how animals can respond to changes in the world around them.

Shorter days, weather changes, scarce food, and instinct help birds begin migration.

Key Vocabulary

Word	Meaning	Example
migrate	to travel from one place to another at a certain time of year	Many birds migrate before winter.
daylight	light from the sun during the day	Shorter daylight can signal autumn.
instinct	a natural feeling that helps animals know what to do	Instinct helps birds begin migration.
scarce	hard to find or not enough	Food can become scarce in winter.
internal clock	a natural timing system inside a living thing	A bird's internal clock helps it notice seasons.

Reading Comprehension Questions

1. What happens to daylight in autumn?
2. Why is food important for migration?
3. What is instinct?
4. What does an internal clock help birds do?
5. Name two signs that help birds know when to migrate.

Answers

1. The days become shorter in autumn.
2. Birds need enough food to survive, and food can become scarce in cold weather.
3. Instinct is a natural feeling that helps animals know what to do.
4. An internal clock helps birds respond to seasonal changes.
5. Daylight, weather, food, instinct, and internal timing can help birds know when to migrate.

Short Summary

Birds know when to fly south by sensing shorter days, cooler weather, less food, instinct, and internal timing. These signs help them begin migration before winter becomes too difficult.

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