1. Hickory Dickory Dock: The Biological Clock Interactive Slide Show

2. Ahhh … the sun! Did you know that the sun is what makes an animal ’ s biological clock go tick tock?

3. That ’ s right … it tells some fish, like these salmon, when it ’ s time to grow big! It also tells them when it ’ s time to swim upstream, to go lay their eggs so they can hatch their babies:

4. It tells chickens like these …. When to lay eggs like these in the summer … And it tells them when to stop laying eggs in the winter, too!

5. It tells a big hawk …. And a little hummingbird …. When it ’ s time to fly south for the winter!

6. But just how does the sun tell animals these things? Here are some hints …

7. Hint 1: This is what eastern Washington looks like in the summer, when the hawk is there: And this is what pictures of the sky might look like throughout a summer day: 5:00 a.m.7:00 a.m.12:00 noon4:00 p.m.9:00 p.m.

8. Hint 2: This is what eastern Washington looks like in the fall, when the hawk is just leaving to fly south: And this is what pictures of the sky might look like throughout a fall day: 5:00 a.m.7:00 a.m.12:00 noon4:00 p.m.9:00 p.m.

9. Hint 3: And this is what eastern Washington sometimes looks like in the winter. The hawk is long gone by now! And this is what pictures of the sky might look like throughout a winter day: 5:00 a.m.7:00 a.m.12:00 noon4:00 p.m.9:00 p.m.

10. So now, can you figure out how this: can tell these: when to do these things? Lay eggs Fly south

11. Now you know how the sun makes their biological clocks go tick tock!