One of the great enjoyments for me as a relatively new birder is the thrill of seeing and observing new species. I love to sit and observe, learn the biology if you will. One of my mentors in photography calls this "putting in your time" and I think that is a very good description. The best photographers are visual communicators and you can't possibly be a good visual communicator unless you understand the intimacies of your subject. The best place to start with wildlife is learning the biology.
A few months ago I had this little fellow visit my feeders. Fortunately I was home at the time and was able to make my way outside quickly with my 600mm lens in tow. It ends up this Yellow Shafted Northern Flicker was only around for a few hours. My observation time with him was only about 15 minutes and I have not seen him again :-(.
Looking at the top image, you will notice the underside of his tail is yellow. These are in part what are referred to as "flight feathers". There are 2 easily distinguishable species of Northern Flickers in the U.S. The yellow shaft which finds itself in the eastern half of the U.S. has yellow flight feathers while the red shaft found in the west has red flight feathers. The other major difference between the two species is their mustache! You will notice on the bird above that there is a black mustache coming from his beak. In the red shaft variety, this mustache is red and in the yellow shaft variety the mustache is black. Its amazing what you can learn from a short visit by a new species in your own backyard!