Tyler and Karl both have good points about the clothing and the lens. As I'm not a "birdwatcher" as much as I am a "photograper", I'm out to get photos, which means I have to get close - much closer than just to watch with bins or scope. And camo WILL make a great difference (in this sense camo also includes Blinds or "hides' as they call them in merry old England). I've had birds land right next to me, and birds and varmints swim right past me not 3 feet away while I was sitting on a canal bank in home-made "camo". I've even fed wild birds sitting right in my hand while camoflaged. They simply did not see me (or perhaps did not recognize me as an intruder). In fact, I've had people completely overlook my presence as well. It's rather amusing to see and hear the surprise people have when they suddenly realize they're standing 2 feet from somebody sitting out in the open taking photos and they weren't even aware of it until I moved.
Being able to take photos so close to wild creatures, as if you're just another part of nature is also a rather exilerating experience. But to accomplish this you have to consider not only your clothing, but also shoes, face, hands, head and camera gear (camera, lens and tripod, bags, etc.)
The real trick is not so much to look just like your surroundings, as it is to blend in and break up your shape/pattern (blur is perhaps a good analogy) against your surroundings. Surplus military camo clothing is a good start, and often they carry surplus camo netting you can use. Hunting/sports supplies will have camo gloves, masks/balaclavas, hats, boots and clothing. In the fall/winter, places like Walmart in the US carry blinds, camo burlap, gloves and other hunting type clothing and accessories in camo. My camera bags are actually camo bags use for duck hunting to carry gear. Works great too. If anyone is really interested, I'd be glad to share details of the stuff I use. My camera and tripod camo covering are homemade, as is my face mask and "ghille" drape, and portable blinds, but I won't bore you with such details unless there is an interest.
I should think for birding, using good stalking technique, combined with basic simple camo clothing would be an improvement over not using such. But for photography, camo (sometimes combined with a "blind") is practically a must for getting close. It simply depends on what you're after.
(I've had several inquiries since this initial post, so I've created these web pages with "how to's" and photos that cover the stuff I've made and use - http://www.outerbanksguidebook.com/ToolsIndex.htm - if this doesn't answer all your questions, then please feel free to email with specifics)
OBXGuide (Fred)
OuterBanksGuidebook.com & NCBirds.com
