Photo/IllutrationA frog impaled on a thorn by a bull-headed shrike (Provided by Osaka City University lecturer Yusuke Nishida)

People in snowy regions like Hokuriku along the Sea of Japan coast have an autumn tradition of forecasting the coming winter's snowfall by observing “hayanie,” or prey that bull-headed shrikes have impaled on thorns or tree forks for storage.

If they find many insects and small animals impaled at high places, they expect heavy snow. If victims are left hanging low, they anticipate a relatively small amount of snow.

While it is not clear whether bull-headed shrikes (Lanius Bucephalus), called “mozu” in Japan, have the ability to forecast the weather, this small predator’s grisly dining habit, which has earned it the moniker “butcherbird,” has piqued people’s interest from ancient times.

A dead frog with rigid limbs impaled on a long thorn is reminiscent of crucifixion. A grasshopper that has gone dry on barbed wire is painful to see.

The songbird’s hayanie impaling habit is described differently in various regions, including “mozu no do zashi” (trunk piercing by the butcherbird), “kushizasi” (skewering) and “hiboshi” (drying in the sun).

Traditionally, this hayanie pantry has been believed to be used to store captured prey for later consumption, probably in midwinter, when there are fewer animals or insects to prey on.

But two researchers at Osaka City University led by Yusuke Nishida, a specially appointed lecturer, have challenged this established theory.

They cycled around woods located near human habitats in southern parts of Osaka Prefecture observing hayanie. They counted the numbers of impaled prey and checked how they had been eaten.

They also recorded male shrikes singing in their own territories and analyzed their voice prints.

“We found that male shrikes that have eaten more impaled food are in a better nutritional state and can chirp faster,” Nishida says.

They also discovered that males that can sing energetically have better chances of mating early.

The two scientists said they discovered and observed 2,099 impaled victims of butcherbirds. While some were not completely eaten, the findings indicate that shrikes hoard prey for later consumption as part of their efforts to be in better shape to attract females.

Their new, more detailed theory concerning the shrike’s prey hoarding habit was published in May in the international ethology journal Animal Behavior.

When you hear the recordings of the male shrikes singing that the researchers made you can instantly recognize differences in the ways they sing. Males that are popular among females sing more quickly and cheerfully than those that are not.

Upon seeing a hayanie, you are left with only the impression that the bird is a cruel predator. But it appears that shrikes also face a fierce struggle for existence.

--The Asahi Shimbun, Nov. 10

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Vox Populi, Vox Dei is a popular daily column that takes up a wide range of topics, including culture, arts and social trends and developments. Written by veteran Asahi Shimbun writers, the column provides useful perspectives on and insights into contemporary Japan and its culture.