What’s the difference between birds that get killed by cars, and those that don’t?
The dead ones tend to have smaller brains, scientists who performed 3,521 avian autopsies said Wednesday.
What might be called the “bird brain rule” applies to different species, depending on the ratio of grey matter to body mass, they reported in the journal Royal Society Open Science.
Crows, for example, have big brains relative to their size, and have shown a remarkable knack for navigating oncoming traffic.
While picking at road kill on Florida highways, earlier research showed, the scavengers learned to ignore cars and trucks whizzing by them within inches, but would fly away just in time when threatened by a vehicle in their lane.
“I don’t know if we can say they are ‘smarter,’ but they do exhibit cognitive behaviour that makes them likely to survive,” lead author Anders Pape Moller, an evolutionary biologist at the French National Centre for Scientific Research, told AFP.
Pigeons, by contrast, appear to be less adept at avoiding collisions, a deficiency visible in compressed form on most big-city streets.
Not coincidentally, they have teeny-weeny brains.
More surprisingly, the relation between brain size and traffic accidents also holds within the same species, the study found.
“Common European blackbirds, house sparrows and robins all show this difference in individuals that were hit by cars, and those that were not,” Moller said by phone.
Undamaged brains from birds killed in accidents—weighed to within a hundredth of a gramme—were consistently smaller, he said.