As mentioned in February, the National Wildlife Federation holds an annual photography contest, which includes categories for pros, amateurs, and children 13-17.
This year's contest just began accepting submissions. The deadline is July 14. Along with submitting, you can also vote for the People's Choice Award.
Check out the Web page here.
Children 12 and under can submit to the Ranger Rick photo contest, which has winners announced every four months with deadlines January 31, May 31, and September 30.