To get inside the head of a homing pigeon as it navigates towards its roost, researchers turned a flock of pigeons into cutting-edge techno-birds. The scientists outfitted the birds with "neurologgers" consisting of an electroencephalograph (EEG) to read the bird's brain waves and a GPS tracker to record its location; by matching a bird's position to its brain activity, the researchers could determine the bird's reaction to the landscape below it. They found that, just like humans, the pigeons use visual landmarks in their navigation.
How homing pigeons find their way back to a starting point is not completely known. Studies have shown that the birds variously use the position of the Sun and the Earth’s magnetic field as a compass, and sense of smell and visual cues as navigation aids. But the use of visual cues has been difficult to study, because if a bird flies over a landmark and doesn’t change its course, it’s impossible to know whether the bird has not perceived the cue or is ignoring it [The New York Times].
For the study, published in Current Biology, lead researcher Alexei Vyssotski released the outfitted birds over the Mediterranean, and saw the
activity in one particular frequency range plummeted as the birds flew across the featureless sea. Brain waves in this band, however, perked up as pigeons neared the coastline, and when Vyssotski's team released pigeons in a city, the same frequencies spiked when the birds crossed prominent landmarks, such as highways [New Scientist].
Researchers also detected two surprising blips while birds were flying over a unremarkable rural landscape; when the scientists visited those locations, they found thriving pigeon colonies that presumably caught the fliers' attention. There were a few other unexpected quirks.
Pigeons flying in flocks also produced fewer of these brain waves than pigeons flying solo. "When animals are flying in flocks it is not necessary to look at landmarks," Vyssotski says [New Scientist].
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