M: Autumn, or fall, is the season between summer
and winter. The days become shorter, and the air
gets cooler. Trees sense these changes, so they
start preparing for colder weather.
Trees that have leaves block water and food
from coming through the branches to the leaves.
When this happens, the leaves die. They fall off
the tree or the wind blows them away. This is
why autumn is usually called fall in America. As
the leaves start to die, they appear to change
from green to red, yellow, orange, or brown.
Actually, the leaves are really these colors all
year long. They look green because of a chemical
called chlorophyll. Chlorophyll works with the
sun to help the trees make food. In autumn,
when there is less sun, the tree cannot make
chlorophyll, so the green color fades. This
reveals other colors, like red and yellow, that
were always in the leaves.
Like trees, animals also sense changes in the
cooler autumn climate. Animals that hibernate
eat a lot during autumn. They gain weight to store
energy in the form of fat. They use this energy to
survive the winter while hibernating. Many birds
survive the cold in a different way: they leave.
Each year, many birds migrate south to warmer
climates during autumn. They migrate north
again in the spring. Not a bad idea if you ask
me! After all, who would refuse a mid-winter trip
to sunny Thailand?