Black-capped Chickadee Print - In Winter Pine Snow Scene

Snow on the pine bough. A small bird, entirely unbothered. The Black-capped Chickadee perches in the winter-weighted needles, black cap and bib reading crisp against the pale scene, buff flanks warm against the cool white around it. This is the season plate for the bird that never leaves.

Poecile atricapillus does not migrate. It holds its territory through northern winters when the temperature drops to minus 20, and it survives by means that are, on close inspection, astonishing. Each autumn the bird’s hippocampus - the brain structure responsible for spatial memory - enlarges by roughly 30 percent. It does this to cache thousands of seeds in separate hiding places across its territory, each stored singly and each location memorised individually. By spring the cache is gone and the neurons that held the map dissolve. The brain rebuilds itself each year around the demands of the season.

A bird that caches uses the winter light differently from one that simply forages. Every visit to the feeder is also a survey of the territory. Every seed carried away is placed somewhere specific and retained. The bird weighing nine to 14 grams on the pine branch in this plate is running one of the most precise spatial memory systems in vertebrate biology.

On the coldest nights it practises regulated hypothermia, dropping body temperature by up to 10 degrees Celsius to reduce the overnight caloric burn, then shivering back to operating temperature at dawn. It has been doing this for whatever winter it finds itself in. This one happens to be on a pine, in the Audubon tradition, on a wall.

Full field guide: /species/black-capped-chickadee/