Downy Woodpecker. Photo by Retriever. Nice catch, R!
Shot with a Canon 7D, with Canon 300mm f2.8 vr lens with a 1.4 extender. A sharp hand-held shot is almost impossible with the lens at 300mm never mind 600mm equivalent with extender.
I should explain a bit for those unfamiliar with lens differences. This was shot with an extreme telephoto lens. It super magnifies, thus the tiniest shake while the shutter is briefly open for the exposure results in a blurry photo, so photographers usually use tripods with a shot and lens like this. Even with a steady hand, you need a lot of luck or many shots to maybe get one clean image. These lenses may have image stabilization built into the lens (or stabilization software may be built into the camera), but stabilization can only compensate a little bit on these long telephoto shots. Adding to the difficulty, these lenses are heavy and extend far out from the body of the camera, making it even more difficult to shoot while keeping a steady hand.
The higher the mm of the lens the more telephoto and magnified. By comparison, I like to shoot a wide lens 18.5 mm for street shooting or occasionally 10mm at a passenger sitting across from me in a subway car, opened up big (letting lots of light in), so I don't have to maintain a super-steady hand to get a sharp shot, but I do have to get up close to get a sharp shot.