The weather gets colder，the days get shorter and the leaves change colours and fall off the trees.Soon，winter is here.Snow c（1）

overs

overs

the ground.People live in warm h（2）

ouses

ouses

and wear heavy coats outside.Our food comes from shops，but what happens to birds？
   Birds do many different amazing things to get t（3）

hrough

hrough

the winter.Some of them migrate.This means they travel to other places where the weather is much w（4）

armer

armer

，or where they can find food.
   Many birds migrate in autumn.Some travel in large groups，because the trip can be d（5）

angerous

angerous

.For example，wild geese fly in noisy V-shaped groups，while some other birds fly a（6）

lone

lone

.
   How do they know when it is the time to l（7）

eave

eave

for the warm place？Scientists are still studying this.Many scientists think migration is part of a yearly cycle of changes that a bird goes through.The cycle is controlled by changes in the amount of daylight and the weather.
   Birds can fly very l（8）

ong

ong

distances.For example，the Arctic terns live close to the North Pole（北極）in summer.In autumn，they fly south，all the way to the South Pole.Each spring they r（9）

eturn

eturn

to the North Pole.
   Most birds migrate shorter distances.Do you know how they find their way to the s（10）

ame

ame

place each year？Birds use the sun，the moon and the stars for the direction.