I know the birds of our region pretty well, but it was only recently that I learned to properly ID the Brown Creeper, despite the fact that they're quite common around here. They're drab, but their behavior clearly distinguishes them from all the other species in our area. I had seen one a week prior, and I texted my dad a description—which is a lot more fun than looking birds up on the phone.
There are only a handful of birds in New England that will hop up the side of a tree: woodpeckers, nuthatches, and creepers. And creepers are unique because they only go upwards, typically in a spiral pattern, unlike nuthatches and most woodpeckers, which can go upwards or downwards headfirst.
Of course, once you learn a common bird well, you start seeing it everywhere, and sure enough, today I saw creepers twice. I was able to get a pretty good shot of this one hopping up the underside of a branch, which is ability exclusive to the aforementioned woodpeckers, nuthatches, and creepers. It's also an ability that's highly advantageous when you're hunting for insects below the wood's surface and the top side of every branch is coated in snow.