Stay out of their way
That brilliant yellow finch by your feeder has been skittish about being your subject for days. Better to get the dramatic close-ups from a little distance. This Sigma Photo 105mm f/2.8 macro telephoto is an excellent choice for getting great nature shots without spooking your subjects. With a nearly silent Hyper-Sonic Motor powering the precise autofocus, it'll almost be like you're not there.
It belongs in your camera bag too
While this macro lens is optimized for full-frame cameras, APS-C cameras can benefit as well. The focal length will increase by a factor of 1.5X on most APS-C cameras (1.6X on Canon's APS-C models), so this 105mm lens will have a 157.5mm equivalent length on many non-full-frame cameras. With several mountings to choose from, this lens has the versatility to find a home in almost any photographer's bag.
Carefully machined low-dispersion optical elements and proprietary coatings yield a lens that is sharp, clear, and free of artifacts like color fringing, ghosting, flaring, and distortion. And built-in optical stabilization reduces the effect of shaky hands on pictures with slower shutter speeds.