Long-Distance Travel May Make Migratory Birds Smarter

Migrating birds that travel great distances may be better at navigating the skies than birds that stay close to home, according to researchers from the University of Oxford. A recent study on turtle doves and reed warblers revealed that the proportion of new neurons generated in regions of the brain responsible for navigation and spatial orientation increased with travel distance.

This discovery also confirms a widely-held theory that cells that specialize in processing and transmitting information and contribute to brain plasticity are continually being generated in the brains of animals, even when they are adults, according to a news release.

Researchers captured 12 turtle doves and six reed warblers in nets in the Jordan Rift Valley in Israel. These birds regularly travel from Africa to the Middle East or Europe. Turtle doves, for example, can travel upwards of 3,480 miles during a single round-trip.

Interestingly, researchers found a distinct difference between the two species in the areas of the brain that incorporated the new neurons. In reed warblers, which migrate as individuals at night, new neurons were found mainly in the hippocampus -- a region associated with navigation. However, in group-migrating turtle doves, the new neurons were found mainly in the nidopallium caudolateral -- an area associated with communication skills.

To estimate the flight distance already taken by each bird, researchers measured the isotopic signatures on individuals' feathers. The known values of isotopes of carbon and hydrogen, found in the water, soil and plants, differ based on where the birds travel. Therefore, researchers are able to match known local values of isotopes with the particular values found on the feathers when the bird was captured.

These migration distances were then compared to the amount of new neurons incorporated into the birds' brains, which was accomplished by selectively coloring brain cells. This was done twice: Once when the birds were first captured in order to identify new cells, and then again a few weeks later to identify neuron cells. The idea is that those colored twice represent new neurons.

Overall, researchers found both species showed a trend of increasing new neurons in line with migration distance and that different brain regions were affected respectively.

"These preliminary findings suggest a potentially exciting, new avenue of research," Dr. Uri Roll, one of the study researchers from Oxford's School of Geography and the Environment, said in the university's release. "What we humans do during the day may actually make us more 'brainy' as our regular activities may actually determine how our brains adapt and in which areas."

Since new neurons migrate to regions of the brain that need them most, their study also helps explain how species evolve.

"For example, other research already suggests that birds that hoard food in particular periods incorporate new neurons in brain regions responsible for memory and spatial orientation," Dr. Roll added. "This latest paper builds on that work, suggesting that birds that need greater navigational help have more new neurons in that part of the brain while those that need to keep up with the flock incorporate new neurons in a different area."

Their study was recently published in the journal Scientific Reports.

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