If you see a collared bird and you have a good scope, try to read the numbers and letters and make a note of the color of the neckband. This information is of great value to biologists who follow their migrations and wintering habits in order to better protect them. If the birds' heads are down and you want to see them, wait quietly for them to look up. They will eventually. Don't go onto private property or down private roads to see them.
Wonderful things happen for the polite birder.
I'm about to get myself into major trouble here if I don't preface my tips for telling Trumpeter swans from Tundra swans. This doesn't always occur in the species. Anomalies pop up all the time. Then just go out there and take a shot at a good guess. A good friend of mine tells me that the difference between a novice and experienced birder is that the experienced birder won't say his guesses out loud.