When you take a picture, you own the copyright. In almost every scenario that you can think of. If you want to maximize something called "Statutory Damages", however, and really get the money out of your stolen images that you feel you deserve, you need to properly copyright your work.
The difference can change an award from a few hundred dollars to $150,000.00
The below video will show you exactly what to do. To skip past the normal show stuff, head to time index 2:50.