With its iconic song that sounds like “cheeseburger,” the small white-and-black common bird flies from pine tree to pine tree.
They live in one place, and during winter snow, it’s a fight for survival because they need to eat constantly, said Vladimir Pravosudov, biology professor at the University of Nevada, Reno, who contributed to the recent report. But it’s not an all-you-can-eat buffet — they need to remember where they store their pine seeds.
“Every fall, they cache surplus food, and they will scatter it. They will stick it in lichens, branches everywhere. The harsher the environment, the more need for memory they have. If they don't find food, they’re just going to die,” Pravosudov said.
Those with better spatial cognition live longer. Neurons in the brain record locations, like computer codes, and start firing when a chickadee looks in the direction of its stash.
It’s this trait that makes them attractive to the opposite sex.
“That will significantly increase females’ reproductive success or fitness, because if she will mate with a male with better cognition and produce young with better cognition, then they will live longer, they will reproduce,” Pravosudov said.
But females don’t always shack up with the smartest male in the flock. It could also be based on who's available. Pravosudov said DNA evidence shows several chicks from one nest can have different bird-daddies.
“The female will spend the night in the nest, and then the male will spend the night sitting somewhere nearby. And in the morning, when it starts getting light, the male will start singing, and the female usually comes out, and then they go away. But the female could actually sneak out before that and then come back very quickly,” Pravosudov said.
He said it only takes one second to mate.
Males with better cognition will sire five to six extra chicks per year, Pravosudov said, but science can’t explain how females determine who has the best memory.
“The male with better cognition will sing more. The other, more controversial but I think very interesting thing, because these birds live together, they see them every single day throughout the winter, which means they’re foraging together. It’s hard to show, but it is possible that they have some idea how good these males are,” Pravosudov said.
Say what you will about these Casanovas, but their offspring do have a better chance of surviving winter.
