Cuckoos are migratory birds that are surprisingly successful at making their way to their summer homes, according to a recent study by the University of Copenhagen. The birds' highly complex individual decision-making process suggests that navigation in migratory birds is more complex than previously thought. 

Cuckoos use their decision-making skills to find their way from unknown locations, researchers from the university's Center for Macroecology, Evolution and Climate explained in a recent study, adding that such behaviors have never been documented in migratory birds. 

For their study, researchers fitted 11 adult cuckoos with miniature satellite tracking devices and relocated the birds from Denmark to Spain -- about 1,000 km off course -- just before their winter migration to Africa was about to begin. This experiment was aimed at testing how the birds would respond when pointed toward different stopover areas used along their normal route, according to a news release

"The release site was completely unknown to the cuckoos, yet they had no trouble finding their way back to their normal migratory route. Interestingly though, they aimed for different targets on the route, which we do not consider random," Mikkel Willemoes, one of the study researchers and a postdoc from the University of Copenhagen, explained in the release. "This individual and flexible choice in navigation indicates an ability to assess advantages and disadvantages of different routes, probably based on their health, age, experience or even personality traits. They evaluate their own condition and adjust their reaction to it, displaying a complicated behavior which we were able to document for the first time in migratory birds."

Of the 11 displaced cuckoos, researchers found one flew to Poland, one to the Balkans, one to Chad and three to the Democratic Republic of Congo. From there, the birds followed their familiar migration route, though the last five birds lost their transmitting signal. 

"In order to select an individual strategy, the birds should be capable of balancing perceived gains and risks of several different scenarios. Such a task would require knowledge of the current location in relation to all of the possible goals as well as distances to each of the goals. This tells us that bird migration in general is far more complex than previously assumed," Willemoes added

Next, researchers plan to develop even smaller transmitters so that they can follow young cuckoos as they make their first relocation decisions without prior migration experience. Cuckoos are particularly useful for navigation research because adult birds lay their eggs inside the nests of others, so when young nestlings grow up without siblings or biological parents to lead the way on new, long migrations, their inherent abilities reveal interesting and complex decision-making strategies. 

Cuckoos belong to a diverse family of birds known as Cuculidae, all of which have a diverse range and are insect-eaters.

Their study was recently published in the journal Scientific Reports.

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