Two more questions....did you use an UV filter and a tripod?
Sorry, I left the tripod question unanswered.
Yes, when at all possible I use a tripod, and a sturdy one. This goes all the way back to my photography classes in my college years.
My teacher said he could ALWAYS tell a tripod used photo upon close inspection due to additional sharpness. This set off my "b.s. meter," but then I discovered this to be pretty darn accurate, especially when shooting with long lenses!
For instance, I could NEVER have gotten the Blue Indigo shot above this detailed in the feather area without a tripod on THIS shot! Why?
The "normal" rules for an acceptably "sharp" shot:
1. 1/lens length in mm = MINIMAL shutter speed. I was using a 400mm so this would equal 1/400th second. HOWEVER . . .
2. For birds, since they jump and jerk around continuously, this normal rule is DOUBLED . . . so 1/400 x 2 = 1/800th second MINIMUM, and twice this amount is preferred anyway if the light is bright enough to get that fast a shutter speed.
In this new, DIGITAL SLR age we have a new rule addition . . .
3. Except for very expensive professional DSLR cameras, the makers use "crop sensors." Nikon's crop camera sensors are 1:1.5. Canon? 1.6. In other words, to keep costs down, the image sensors in consumer-priced DSLR cameras are much SMALLER in size by a factor of 1.6. HANG ON, I'm almost done . . .
Thus my 400mm lens only "sees" a smaller portion of its available image on the small sensor, by the ratio 1.6. 400mm x 1.6 = an effective focal length of a 640mm lens!
Going back to rule #2, TWICE the shutter speed of my 400mm on my Canon "crop body" is 1/640 x 2 = 1/1,280th of a second MINIMUM! Yes, the T3i, and even Canon's premiere Birding camera, the 7D are also 1.6 crop cameras. Greater lens length is always good for birding!!!
NOTE: Many photographers brag that they can shoot a 400mm, handheld, and get very sharp photos most of the time. They are right, but wrong. The photos may be 'acceptably' sharp in their opinion as they look beyond the flaws, but most of these images would not be commercially sharp.
TIP: ALWAYS make sure the bird's EYE is in sharp focus, or the photo will fail. It must always be sharp. Period!!!
BACK TO THE IMAGE. It was shot near last light. I know from experience that even with a tripod, the slowest I can SOMETIMES get away with is 1/125th second with a very still bird . . . which an Indigo Bunting rarely is!
For the mere 1/125th second that the lens was open on THIS shot, the bird had remained totally still. I got LUCKY as the camera rested on a very, very steady tripod!!! The very next shot in my two shot burst was blurry as heck because the bird moved almost imperceptibly.
Hope this helps! Tom