Gathered around a bonfire on the Winter Solstice, the hostess asked us each to share one moment from the past year that made us go, “Wow!” Despite the fact that my year had included rafting the Colorado River through the Grand Canyon, my favorite “wow” moment happened on a river much closer to home. One lovely afternoon last May, I set out with a friend to paddle an upper section of the Namekagon River. Approaching a bridge, a burst of twittering, movement, and flashes of yellow in the alder shrubs drew my attention. Squinting, I thought I spotted a black cap on one of the tiny heads, and quickly pulled into an eddy.

Sure enough, our binoculars revealed a flock of half-a-dozen or more little birds, “yellow as a lemon, with a smooth, black cap…” as Mary Oliver described them. Laughing in delight, we felt like we’d just conjured these Wilson’s Warblers with her poem.

Chickadees cache as many as one hundred thousand food items per year. Not only do chickadees remember their seed cache sites, but they also remember details like which food items were the most favored and which seeds have already been eaten by them or by a thief. To support such an incredible memory, chickadees grow 30 percent more neurons in the fall when caching behavior peaks. Last April, researchers at Columbia University added to our understanding of chickadee memory. They discovered that chickadees create “neural barcodes” and essentially create their own system for inventory and checkout—just like at a grocery store!

While digesting one of the many rounds of holiday feasts and leftovers, with plates of cookies in between, a headline caught my eye: “Big brains or big guts: Choose one.” As much as the post-holiday-dinner-brain-fog is real, I don’t love the implications of those options. Luckily, the article wasn’t about humans. It was examining birds in cold, highly variable habitats, and their struggle to survive. Essentially, birds have two options: spend energy maintaining a big brain that allows them to find high-quality food, or spend energy maintaining a large stomach that can make low-quality food sufficient in high quantities. According to the research, if you are a bird who needs to survive cold winters, you must choose one. There’s no middle ground.