Beautiful photos here guys. As a professional photographer, I'd like to mention something contrary to what the original poster has said. This may have been covered and if so, I apologize.
I merely want to point out that ALL photographs are copyrighted, not just some. Posting them does not make them a part of public domain either. Nothing need be done either to copyright images. The Library of Congress recognizes that a work is copyright as soon as the image is recorded (shutter button released and written to card or recorded on film) so my just pressing the shutter release, my work is copyrighted.
If a hobbyist were to catch someone using an image without permission, then they would have the right to sue for actual damages based on the value of their work. The burden of proof lies with the photographer to prove the images belong to him. If that person has also taken the time to send the images to the Library of Congress to register them then he can also sue for punitive damages as well up to $10,000 per image and there is no burden of proof because they are already registered.
When using someone else's work, please make every effort to contact them. Most photographers are just hobbyists and would enjoy sharing their work with people who ask. This is all just FYIO.
Enjoy and keep the great photos coming.