Photo/Illutration A shrike nest on southwestern Kikaijima island was found for the first time in 2012. (Provided by the National Museum of Nature and Science)

Timid birds of the shrike family are more likely to resettle in different, far-flung habitats than their bolder counterparts, according to a study that turns established theory on its head.

Shrikes live in the same areas on the main island of Honshu for almost the entire year. But some of them migrate to the southwestern Nansei islands in Kagoshima and Okinawa prefectures in winter.

A research team, led by the National Museum of Nature and Science, found that more cautious ones were more apt to settle on thosee islands.

Studies recently confirmed that shrikes now live on Nakanoshima island of the Tokara island chain, Kikaijima island of the Amami chain, and Minami-Daitojima island throughout the year.

Based on studies in city areas, a general theory was accepted that bolder animals that take risky actions were more apt to settle in a different environment.

Shoji Hamao, head of a vertebrate study group at the museum, and other members calculated the “boldness” level of the shrikes.

During the birds’ breeding season, the researchers measured the distance when the shrikes took flight to escape approaching humans.

They found that 56 shrikes in the three islands flew away when the humans were 50.5 meters away on average.

On the other hand, 66 shrikes in Kagoshima, Ibaraki, Hokkaido and other mainland prefectures took flight when the humans were within 26.1 meters on average.

On the Nansei islands, shrikes use shrubs as breeding sites, but black rats steal their eggs and attack their chicks.

“Shrikes in the Nansei islands overturn the established theory,” Hamao said. “Only careful individuals that can flee in a hurry or move their nests to different places when they notice approaching black rats were able to leave their offspring.”

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