Ruby-crowned Kinglet

I shot this earlier in April when I was using the older 500mm lens (I was feeling lazy/sore and wanted to go a little lighter than my 800mm).  Ruby-crowned Kinglets are always hyper and getting one to stop still for a moment, much less one where I can frame it and focus on it in that timeframe, always involves throwing out at least 90% of my attempts which are usually a comical mix of subject blur and fragments of tail feathers as most of the bird has already left the scene.

Although in this case the fact that I was shooting prior to full leaf-out (due late April) raised the odds slightly.   The 500/4L is a little faster to focus than the 800/5.6L which probably helps.

Ruby-crowned Kinglet

First fall immature, Central Park, Oct 8th.
These birds are hyperactive, so most of my images of Ruby-crowned have a dubious level of blur about them. It's a borderline nemesis bird for that reason, especially for a relatively common species. Golden-crowned Kinglet and Wilson's Warbler have the same challenges - they never pause, especially in migration when they are looking for food after flying all night. The odds were enhanced in this case by it being a sunny day, so a higher shutter speed helped. And also a large amount of luck.