Mountain chickadees have an extraordinary memory

Ever misplaced your keys or forgotten where you parked? Imagine if you had the remarkable memory of a mountain chickadee. Despite their small size, with brains just larger than a pea, these nimble birds masterfully remember the locations of tens of thousands of food caches. 

Mountain chickadees hide seeds in tree bark, under dead leaves, and within pine cones throughout mountainous terrains. Their ability to recall these locations during the harsh winter months is crucial for their survival amid the cold and snow.

Remarkable memory of mountain chickadees 

A research study led by the University of Colorado, Boulder and the University of Nevada, Reno has identified nearly a hundred genes that are linked to the birds’ spatial memory, which is their ability to pinpoint and recall the locations of these hidden caches. 

Furthermore, the experts suggest that there might be a trade-off between having robust long-term memory and the ability to quickly forget old memories to make room for new ones. This discovery has the potential to deepen our understanding of how spatial memory evolves not just in animals, but also in humans.

“Chickadees are impressive birds,” said senior author Scott Taylor, the director of CU Boulder’s Mountain Research Station and an associate professor in the Department of Ecology and Evolutionary Biology. 

“They can remember tens of thousands of locations where they cached food across an entire winter and a new set of those the next winter. Their spatial memory is much more developed than many other birds that don’t have to have this strategy to survive cold winters.”

Focus of the research 

To assess how these birds manage such a feat, Taylor’s colleagues at the University of Nevada, Reno, led by biologist professor Vladimir Pravosudov, put together a creative test. They set up multiple feeder arrays in California’s Sierra Nevada mountains, each consisting of eight bird feeders filled with seeds. 

Each feeder was equipped with a gate that had a radio frequency reader capable of detecting a tag placed on the chickadees. The setup required the mountain chickadees to remember which feeders they could access as each gate was programmed to open only for certain birds.

Spatial learning among mountain chickadees 

Pravosudov’s team observed and recorded the number of times each bird visited the incorrect feeders before finding the right one. The underlying theory was that mountain chickadees with superior spatial memory capabilities would show a lower rate of errors.

Additionally, using blood samples, the scientists sequenced the genomes of 162 tagged chickadees, creating the largest dataset ever for exploring the genetic basis of cognitive abilities in chickadees. 

Genetics of spatial memory in birds

By correlating the birds’ genetic information with their performance in the feeder test, the team identified 97 genes associated with the chickadees’ spatial learning and memory. Birds with specific genetic variants at these genes demonstrated fewer incorrect attempts before successfully locating their designated feeders.

According to co-author Sara Padula, a Ph.D. student in the Department of Ecology and Evolutionary Biology, a large proportion of these variants are linked to neuron formation in the hippocampus, a part of the brain that plays a fundamental role in learning and memory. “Understanding the genetic basis of this trait will allow us to understand how the trait evolves,” said Taylor.

Moreover, he pointed out that the common ancestor of all North American chickadees cached food. However, among the seven species of chickadees found today, two do not. 

“They live in a milder environment where food is generally available year-round. Now that we know the gene regions that underlie spatial memory, we can look at what variation looks like in these species that have lost caching,” said Taylor.

“This study substantially advanced our understanding of the genetics of spatial memory in birds and behavioral genetics more broadly,” added co-author Georgy Semenov, a research associate in the Department of Ecology and Evolutionary Biology.

Good long-term memory may have a disadvantage

The research also highlighted a potential downside to having an excellent memory. After a few days of the initial task, Pravosudov’s team reassigned new feeders to the birds. Surprisingly, mountain chickadees that excelled in the initial tests struggled with adapting to the new feeders. They found it challenging to discard old memories and form new ones.

“In a more variable environment, what our collaborators found suggests that chickadees with good long-term memory may have a disadvantage. For example, if there is an unexpected snowstorm, these birds may keep trying to visit caches that have been buried in the snow, rather than forgetting them and looking for other caches,” Padula said.

As climate conditions continue to change, birds that can adapt quickly by forming new memories might have a better chance of survival. “Because of climate change, we might expect these selective pressures that have been shaping chickadee’s special memory for thousands of years to shift significantly,” Taylor concluded.

The study is published in the journal Current Biology.

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