If someone calls you a “bird brain,” they don’t mean to compliment you. It turns out, however, that birds you see every day can accomplish astonishing feats of memory.
The outpost of my bird feeder was busy with an orderly crowd of chickadees. Every few minutes one zipped in, selected a sunflower seed, then flitted off to the cover of some trees. They almost never stayed to open the seed. There was never more than one bird on the feeder at a time. Sometimes one would wait on the porch railing if the feeder was already occupied. Occasionally one bird chased another away in a short but furious skirmish.
It was hard to count birds with all the motion, but my best guess was only about four or five chickadees. They worked the scene for more than an hour. How could they possibly eat that much?
The answer is, they don’t. Some of the seeds the birds carried somewhere sheltered to crack open and eat, certainly. Since the feeder was full, they also probably stashed many of the seeds for future meals: in crannies of tree bark, under the roof shingles, or other small nooks.
Chickadees belong to one of the few families of birds that cache incredible amounts of food — and can find it again. The list also includes nuthatches and corvids (jays, ravens, and crows).
Unlike squirrels, who go for the treasure-horde method of food storage, chickadees cache seeds one at a time. That way, if another bird sees them make the drop-off and steals the prize, it only pilfers one seed. If a bird trying to secret away a seed notices a neighbor spying on the proceedings, it may simply fly off to another location. Alternately, it may wait until the nosy neighbor is gone and rehide the seed.
What’s truly amazing isn’t the sheer number of seeds chickadees can store, but that they remember most of them! Black-capped Chickadees have been observed storing close to 1,000 seeds in one day. That means thousands of seeds each winter. They've been tested to remember these locations for at least a month if not longer.
Not only do chickadees remember where they hide seeds, they can remember the quality of the seeds as well. Seeds such as black sunflower are prized because of the high fat content, an essential ingredient to fuel a chickadee’s metabolism through the winter. Like a kid that eats dessert first, the birds will retrieve the best quality (and tastiest, presumably) food first. If, like me, you misplace your phone or your keys because you can’t remember where you put them down, these feats seem almost supernatural.
These memory gymnastics aren’t supernatural, just very specialized anatomy. In bird species that survive by caching large numbers of food items, a portion of the brain called the hippocampus is much more developed than in non-caching species. As in mammals, the hippocampus is strongly involved in spatial memories. Some studies indicate that in Black-capped Chickadees, at least part of the hippocampus breaks down and regrows each year, usually just before the autumn peak of food storage. The bird’s memory of last year’s caches may literally be wiped clean.
The Clark’s Nutcracker, a gray corvid with black-and-white wings that lives in the Rocky Mountains, is the all-time champion of seed caching. These birds remember locations for approximately 2000 caches each year for eight or nine months, the whole winter. Experiments have shown the nutcrackers aren’t just randomly poking around by any large tree stump or rock, but remember specific locations and can find caches quickly when they return.
How do they do it? It’s thought birds that store caches use objects to remember the locations. Possibly they orient by landscape features, then by local ones such as tree stumps or rocks. One researcher moved large objects such as logs near where a nutcracker had buried seeds. The bird moved accordingly, so it was in the same relation to the objects as when it made the cache.
When chickadees watch another bird hide a seed, if they don’t snag it right away, they will probably forget the location. Ravens are a different story.
One of the most fascinating things about bird intelligence is that their brains have developed completely differently than mammal brains. Birds are quite literally an alien intelligence. In mammals, the cerebral cortex is the seat of intelligence. It is largest and has the most wrinkles and folds in species such as chimpanzees and humans.
In birds, the cortex is a small portion of the brain and has little to do with intelligence. The surface looks much smoother than in mammals. For a long time, scientists assumed this meant birds just weren’t as smart. But magpies and crows perform at least as well as dogs on problem solving tests, sometimes outperforming mammals in advanced learning experiments.
Monkeys struggle to learn to tell the difference between counting to two and three. In experiments where ravens and parakeets had to identify which box contained food based on the number of small objects in front of it, they were able to distinguish up to seven objects to retrieve their reward. The seat of bird learning and intelligence, it turns out, is a portion of the brain called the hyperstriatum, which is unique in birds. It is most developed in passerines (small songbirds), parrots, and corvids.
This intelligence is important for ravens. It means they can learn by watching other birds — or remember where they observed another raven caching a tasty morsel of meat. Even more impressive, they can resort to trickery when another bird is watching them. This means they have an awareness of another individual, can anticipate its actions, and take counter measures.
In the wild, ravens that congregate at a food source like a nice, ripe animal carcass will often cache as much food as they can while supplies last. They don’t hide the tidbits close by so they can get back to quickly grab more. Instead, they often fly further away to find a secure, secret location. They may do nothing more than poke a hole in the snow to hide their treat then pile snow back on top, but they will remember exactly where they left it. If they remove a cache, or see another bird remove it, they won’t look for it again.
Bernd Heinrich, in his book of “Mind of the Raven,” relates observing the caching behavior of captive ravens. He describes one day when a raven waited to make a cache until another bird had moved to the far end of the aviary. When she finished, the other raven went to her cache and started to dig in the snow. He hadn’t watched closely enough, so wasn’t successful. She was able to retrieve her snack easily.
The next day, the female raven cached a piece of meat. When she left, the same marauder flew over to the general area she had been in and began probing the snow. Instead of driving him away, she waited until the other bird was occupied, then hastily cached several more pieces of meat. When the other raven started watching her again, she stopped.
It makes you wonder what that chickadee is thinking when its bright black eye catches yours just before it dives off the feeder and out of sight.
• Beth Peluso is a freelance writer and illustrator and avid birder. She enjoys spying on wildlife across Alaska.