Scientists used to think bigger brains made them smarter. Birds can develop sophisticated tools and remember where they hid food, despite the logic that says they can't. According to research published in Current Biology, birds use less energy in their brains than mammals, so they can pull this off.
A study shows that the brains of birds are denser than those of other animals. A squirrel monkey has 30 grams of brain while a macaw has 20 grams. Despite being only 2 percent of the body's mass, the human brain uses a fifth of the body's energy, according to a researcher. Birds have small bodies and energy budgets that are based on how much food they eat.
The researchers looked at the common pigeon. They injected a radioactive chemical into the veins of 10 pigeons and used a scanning device to track the radioactivity through their brains. The researchers looked at the movement and took blood samples to figure out how much brain tissue was consuming. The data from the 2016 paper was used to calculate the amount of sugar each neuron used.
Von Eugen says that a pigeon neuron used three times less energy than the average mammal's neuron. She says that the difference in energy use between mammals and birds is so large that it cannot be the only explanation. She suggests that bird brains are organized so that they can more easily exchange signals. Songs and flight could have pushed the evolution of more efficient brain cells, according to the authors.
She was not involved in the new research but said the finding was pretty remarkable. She says the energy difference is the same as the math you would expect. Birds may have evolved this trait to work with their limited energy supply.
Both Herculano-Houzel and von Eugen are interested in the use of neuron energy in other birds.
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