Researchers have determined that mountain chickadees living at high altitudes in the Sierra Nevada are more intelligent than their brethren lower down.
The findings are part of nearly two decades of research conducted by Vladimir Pravosudov and his team at the University of Nevada at Reno. Science writer Rebecca Heisman reported the story for All About Birds, following Pravosdudov and company into the snowy Sierra to get a peak at how they came to their conclusions.
But how to measure chickadee intelligence? Step one is determining what is meant by “intelligence.” For some birds, like corvids, that can mean a capacity for play and mimicry. For chickadees and other birds in the Poecile genus, it’s all about food caching — a concept any expedition-loving reader of this website can appreciate.
A willow tit, another bird in the Poecile genus that caches food. Photo: Shutterstock
Hiding food? Better have the neurons for it…
Chickadees and tits all over the world cache food. According to Heisman’s reporting, Vladimir Pravosudov first began studying the behavior at the start of his career in the Soviet Union. After migrating to the United States, he ran a study comparing the caching behaviors of black-capped chickadees from Alaska and Colorado.
When the data was analyzed, Pravosudov successfully demonstrated that black-capped chickadees in harsher environments were more successful at caching food than their fair-weather cousins. A series of follow-ups in 10 more locations around the country verified his results.
Researchers concluded that mountain chickadees at higher elevations are better at caching food. They also proved the birds have denser neurons and larger hippocampi than lower-elevation specimens. Photo: Shutterstock
Pravosudov eventually moved to the University of Nevada at Reno. There, he suggested that his grad students pursue similar research on mountain chickadees. Only this time, the scientists would study birds from one population group spread out over different elevations.
In the Sierra Nevada, a winter storm can dump a meter of snow at 2,000m — and double that amount 300m higher up. The differences in conditions served as the perfect environment to test the impact of environmental harshness on a geographically small population of animals.
A study in bear cognition
The research team used radio frequency identification (RFID) bands to let certain birds into certain specially-made bird feeders, according to the study.
“How quickly a chickadee learned which feeder in the array was programmed to open with its matching leg band, and how well it could recall this information later, provided a measure of its spatial memory abilities,” Heismann writes in the piece.
That sounds easy enough, but the team had to contend with the Sierra Nevada’s famously deep snow — not to mention the area’s notoriously intelligent black bears. It took researchers a few tries to come up with a system that would keep the bears out of the bird seed. They eventually hung feeder arrays from the trees using a system of pulleys.
“We joked that we were studying bear cognition for a while,” one of the scientists told Heismann.
A black bear in the Sierra Nevada. It takes a lot of work to keep them out of human food — or in this case, chickadee birdseed. Photo: Shutterstock
In the genes
The eventual results bore out the hypothesis. Mountain chickadees at higher elevations — birds dealing with harsher winter conditions — had better spatial memory. Not only that, but they had larger hippocampi and greater neuron density.
Next, the scientists began studying the chickadee’s genes to determine if the trait was a short-term learned behavior or something encoded over long generations of natural selection.
Turns out it’s the latter option.
For more details on the genetic studies and what researchers at Pravosudov’s lab have next on their agenda, check out the full story at allaboutbirds.org.
