Tiny chickadees grow bigger brains when needed

You put the car keys down somewhere in the house, and have spent 15 minutes trying to find them. You’ve also been known to dash around looking for your hat, forgetting that it’s already on your head.

These kinds of things happen to us humans, but they don’t happen to chickadees.

The reason: Chickadees expand their brains in winter to increase their ability to remember where they’ve hidden bits of food in the autumn. Their spatial memory bank literally grows up to 30% to handle more things needing to be remembered. And being able to call on an expanded memory is what’s going to keep chickadees alive until spring.

These small birds, many living in cold climates, spend most of September and October rushing around, hiding bits of food all over their territory. A single chickadee might hide up to 80,000 seeds and pieces of insects in a season, each in its own hiding place in bark crevices and cavities, and needs to remember where each one is. Come winter, when wild food becomes scarce, these tiny caches can mean the difference between surviving the day or succumbing to the cold.

It may seem hard to believe that a chickadee brain can remember 80,000 food caches, but this has been thoroughly studied by avian researchers, both in laboratory settings and in the wild. Technology breakthroughs have made it easier to study these little birds and their amazing memories and to measure how their brains grow.

Researcher Dmitriy Aronov designed an indoor arena in his lab at Columbia University to conduct live monitoring of brain activity in wild-caught 'dees. As the birds hunted for food they'd hidden earlier, sensors attached to their heads recorded brain activity. When a 'dee returned to one of its hiding places, the sensors showed the same unique pattern of brain activity as when the bird hid that food bit. Almost like a bar code, as one researcher put it, and it proved that the bird was recalling exactly that piece of food in exactly that spot, not just finding it in a random search.

The chickadee has a mental picture of where each hiding place is in its environment, which might include nearby trees, stones or other cues. Few other living things achieve this level of spatial memory.

And how do we know that their brains grow larger in autumn? Chickadees were injected with tracer fluid in the early fall, their brain size measured by sensors, then released. The same birds were caught more than a month later, and were euthanized in order to measure their brain growth. They'd added about 30% more neurons to their brains' memory center.

So why don’t they just grow a larger brain to use all year? They’re constrained by the need to stay light in order to fly well, but finding food takes precedence in winter. Another amazing thing — come spring, those chickadee brains shrink back to pre-winter size, a time when ‘dees can now find adequate food in the wild.

A few other food-storing birds, such as jays, nuthatches and nutcrackers, also add to their brain capacity before winter.

Mind-blowing, isn't it? Back to those missing car keys: The usual advice is to give more attention to where we place things, but wouldn't it be keen if we could just grow our brains?

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.