Only a handful of animal groups are capable of learning complex sounds, defined as the ability to learn and retain a large number of sounds. This is related to brain size and problem-solving ability.
The star has an extraordinary repertoire. Starling, versatile songbirds that learn chirps, whistles, calls and songs throughout their lives are among the most advanced birds in vocal production. Now, a new study published in Science concludes that, among other complex song learners, starlings are also excellent problem solvers.
“There is a hypothesis that only the most intelligent animals are capable of learning complex sounds,” says Jean-Nicolas Audet, a research associate in Erich Jarvis’ lab at Rockefeller University. “If this is true, then animals that can learn complex vocal patterns should also be better at cognitive tasks, but no one has shown that yet.”
Only a handful of animal groups are capable of learning complex sounds, which is broadly defined as the ability to learn and retain a large number of sounds. Humans, elephants, whales, seals, and bats represent the majority of mammals that learn song. Songbirds, parrots and hummingbirds cover the birds.
The Star’s Song
The Jarvis lab has long focused on songbirds, classifying the complexity of their song learning based on three parameters: how many songs and calls are in the bird’s repertoire, whether the bird can continue to learn new songs and calls throughout its life, and whether the Case is can mimic other species.
To find out whether voice learning is linked to the different cognitive abilities of songbirds, Audet and his colleagues spent three years trapping hundreds of wild birds from 21 species using mist nets at the Rockefeller University Field Research Center, a sprawling protected area that encompasses many different ecosystems New York’s Hudson Valley.
“It is a protected area, which means that the animals’ exposure to humans is limited,” explains Mélanie Couture, a research scientist who worked on the study. “This is ideal for studying the behavior of wild birds: what they can do and how they respond to cognitive tasks.”
When assessing their subjects’ vocal learning abilities, three favorites emerged: starlings, blue jays and gray hawks (relatives of mockingbirds). They were also the only three capable of imitating other species (“the epitome of vocal learning,” says Audet).
Next, the team conducted a series of cognitive tests on 214 birds from 23 species (including two lab-bred species that were added to the wild-caught birds). They tested their problem-solving skills by challenging the birds to remove a lid, punch a hole in a sheet or pull a stick to get a treat. Self-control was assessed by placing a transparent barrier between each bird and a snack and recording how long it took for the birds to stop colliding with the barrier and avoid it. Other tests looked at whether the birds could learn to associate a particular color with a food reward and how quickly they adapted when the associated color changed.
Statistical analyzes showed a strong connection between problem-solving ability and vocal learning ability. Starlings, blue jays, and catbirds were not only the most advanced song learners, but also the most adept at solving puzzles, and the better a bird was at overcoming obstacles to obtain a reward, the more complex its learning ability. There was no association between the other cognitive tests and the complexity of vocal learning.
The researchers also found that advanced song learners and problem solvers had larger brains relative to their body size, a possible biological basis for the observations. “Our next step is to analyze the brains of more complex species and understand why they are better at problem solving and vocal learning,” says Audet. “We have a pretty good idea of where in the brain vocal learning occurs, but it is still unclear where problem solving occurs.”
Overall, the results suggest that vocal learning, problem solving and brain size may have evolved in parallel, perhaps to increase biological fitness. Based on these findings, as well as previous work on the ability of vocal learners to dance to a rhythm, Jarvis now calls this set of characteristics the “cognitive complex of vocal learning.”
“Our results support a previously unproven idea: that the evolution of a complex behavior such as spoken language, which depends on voice learning, is linked to the coevolution of other complex behaviors,” says Jarvis.
REFERENCE
Songbird species that exhibit more complex vocal learning are better problem solvers and have larger brains