Snowy owls are sighted in Laoting, Hebei province, which scientists say is a rare appearance of the raptor. [Photo provided to China Daily]

"It is perhaps a once-in-a-lifetime chance, seeing the snowy owl in this place," Li says. There has not been a single sighting of a snowy owl in warmer places in China.

The ghostlike birds live a mysterious life in the Arctic, thus few scientists have spotted or tracked them before. But this winter was different. The alleged Laoting sighting is a case in point.

Canada is the major habitat in North America for the snowy owl, but it is frequently spotted migrating in the United States, including in the southern state of Florida, which has a warmer climate.

According to a report from National Public Radio in March, snowy owls started to appear all over the US around Thanksgiving in Nebraska, Kentucky, even as far south as beaches in Florida and Bermuda. In Europe, snowy owls sightings have been reported in France and the Netherlands since winter.

Snowy owls are typically found in the northern circumpolar region, where the species adopts its summer home. But its relocation to the more southerly latitudes could be attributed to it being a particularly nomadic bird, and that the population of its prey is running low in the northern region.

"The global appearances of snowy owls are definitely related," says Liu Yang, an ornithologist with Sun Yat-Sen University in Guangzhou, Guangdong province, and now a guest research fellow at Harvard University.

"Research shows that the snowy owls in different regions are not different in terms of genetics. In other words, they belong to the same population and behave similarly under the influence of environmental changes," says Liu.

Snowy owls live on rodents and other birds. In the Arctic, lemmings are their major prey.

"Last year was a breeding peak of lemmings in the Arctic, so the population of snowy owls rose rapidly," says Liu.

"Besides, last winter was very cold in the US, that may explain why snowy owls migrated so far south," Liu says. "But it is still very rare to see snowy owls in Florida and Bermuda."