There are certain birds that, based on experience, I can place a very high prior probability on finding in any patch of trees around here. Anna's Hummingbird. American Robin, California Towhee, Ruby-Crowned Kinglet and so on. They're there, I can find them quickly. Most of these species made my bird list for El Cerrito Hillside Natural Area within the first day or two. But there is one bird I have high confidence is in all these patches, but not high confidence in finding. And that is the Brown Creeper, Certhia americana. The Brown Creeper, as its name suggests, is not a flashy bird. Small, brown, spotted for camo, the only American representative of the family Certhidae moves like its old world relatives; it creeps, foot over foot, up surfaces (in this case the trunks of trees) probing cracks and crevasses with its wrenish bill, looking for arthropods. It doesn't make a lot of noise, it doesn't make sudden movements, it is an extremely common bird that most people will never see unless they look for it. I have seen people walk past Brown Creepers that are at head height, five feet from their eyes and in full view, and never know the bird is there.
So I have had my eyes and ears open for the little sneakers ever since we moved to El Cerrito, and been continuously thwarted. Occasionally I will see a flash as something shoots past, flapping like a creeper flaps, but been unable to get a good enough look to confirm the identity. I have heard what I thought was creepers but couldn't be sure. But this morning, Iris and I went for a short walk under the oaks just outside our back yard, and a flash of bitty wings caught my eyes. My brain said "Creeper!" I swung around, unwilling to take my eyes off it as it flitted this way and that through the branches, and then dropped, coming to rest on a tree trunk ten meters from us, fully visible only because my brain knew it was there. Iris and I both raised our binoculars. Sure enough, a Brown Creeper, trickling up the trunk. That swaying foot over foot climbing makes the bird move more like a wavering shadow than a living thing, and the speckles on the bird's back looked like little bits of every kind of bark in the forest. Being reminded of this, I felt a little bit of pride at having spotted this very common backyard bird. I'm sure there are hundreds of them back there.