Leucistic Black-capped Chickadee

Back in October, during a visit from my mom, we spotted a really strange chickadee at the feeder.  We spotted it again later that  day and got a better look at it.  All we could tell about it from a cursory glance is that it had too much white on its back.  A few days later, I was finally able to snap a picture of it.

Black-capped Chickadee displaying leucism.

The white on its back intrigued me, but I had no idea what it was, so I posted the picture to the Illinois Audubon Society facebook page.  A very knowledgeable individual told me that this chickadee has leucism, which is the lack of pigment in isolated patches.  Later, I found this article from the Cornell Lab of Ornithology on the difference between leucism and albanism. 
Albinism and Leucism in birds.

Unfortunately, I haven't seen this little guy since the above photo was taken.  I don't want to think the worst, but I have a neighborhood Coopers Hawk that likes to prey on small birds, and this guy's white patches makes him a bit more obvious to predators.  Here's hoping I get to see my rare friend again soon.