African Babblers Get Dumber With More Babies

Researchers have observed that the female southern pied babbler, a small black-and-white bird found across the southern African savannah, gets less smart as it ages, a correlation tied to the number of chicks she has over the years.

Researchers from the University of Western Australia devised a battery of cognitive tests to assess the birds’ ability to learn associations, adapt to changes, and control counterproductive behaviors.

“Analyzing over 10 years of breeding data, we found that individuals with lower general cognitive performance produced more fledglings per year,” evolutionary biologist Camilla Soravia and colleagues write in Proceedings of the Royal Society B.

The findings suggest a tradeoff: the ability to think and the fecundity of the nest each requires energy, a finite resource. Breeding is fiercely competitive among female babblers and it takes a lot of energy. Collectively, the birds appear to prioritize survival of the next generation over intelligence.

How do we know the babblers aren’t losing brain power as a simple function of age? Because the males don’t change over time.

What we don’t know is whether individual birds truly get dumber as they age or if they are simply living longer than the females that devote resources to cognitive performance. The researchers will need more data taken over a longer period of time to figure this out.

Photo credit: Paul Donahue / iNaturalist & Proceedings of the Royal Society B