Here is another Kirtland Warbler photo which they also call the bird of fire I took this spring at a photogenic Jackpine plantation I found last year, as the trees are five feet high and it had at least 18 singing male Kirtland Warblers in this small remote planting. I never used flash much as I shoot lots of whitetail photos and they will only let you flash them once and there gone snorting all the way back though the swamp.
So I set it to program and it did fair, but this great forum is teaching me fast that flash it a must on birds and working on the right set up.
Looks like you found a nice eye-level perch with a distant BG, and that's half of the battle. The bird looks sharp and well illuminated. Perhaps flash might have helped bring out some detail in the darks, but you may be able to do that in PP. The bird is a little small in the frame; I wonder if a vertical crop would work here? If not, I would crop some off the right and a little off the left also. Thanks for posting!
Pose and details look good and I would be happy to see this species sometime. I would go for a different crop, either crop a bit off right and top or go for a vertical. Thanks for sharing!