Monday

Rocket finds a single feather on the sidewalk. He holds it up to the light. "It is so light!"

Raven looks closely without touching. "Notice the tiny branches. They hook together like a zipper."

Rocket blows on it. It barely moves. "How does something this light keep a bird warm?"

Nova hovers near. "Light, strong and layered," she says. "Ask what each part is for."

Scientists use two words a lot this week.

A structure is a body part. A function is the job that part does.

A wing is a structure. Flying is its function.

Every structure on a bird has at least one function that helps it survive.

Our job is to look at a part and ask: what is this for?

Birds are the only animals with feathers.

Feathers have more than one function.

Flight feathers on the wings and tail are long and stiff. They push against the air.

Soft, fluffy feathers close to the body trap warm air. They keep the bird warm.

Many birds spread oil over their feathers with their beaks. The oil helps water roll off.

Feather colors can help a bird hide, or help it stand out to other birds.

Wings are the structures that let most birds fly.

Flying helps birds find food, escape danger and travel long distances.

Wing shape matters. Broad wings help a hawk soar and glide with little effort.

Short, rounded wings help a small bird dart quickly between branches.

Many bird bones are hollow and light. That makes flying easier.

Structure, function, feathers! Tomorrow you look at beaks, the tools birds carry on their faces.