Every winter, millions of migratory birds visit Korea, offering a treat to birdwatchers and wildlife photographers.

The winged guests mostly come from Northeast Asia, Russia and Siberia, on their way to remote places in Australia and New Zealand.

Although we know surprisingly little about their arduous journey and the troubles they run into along the flyway, one thing is becoming increasingly clear here ― the population of migratory birds is shrinking.

Yubudo, a tiny island off Seocheon, Chungcheong Province, used to get over 5,000 oystercatchers every October, a rare species of migratory bird that has been designated a natural monument in Korea. This year, it received just 2,000.

At this pace, the oystercatchers may just stop coming to the island in the near future, experts warn.

The trend is not confined to Seocheon.

An official governmental census of migratory birds nationwide shows that the population of migratory birds dropped 13.7 percent in 2012 from a year ago.

According to the census, which was conducted in January, a total of 1.08 million birds, belonging to 200 different species, were spotted at over 190 major habitats across the country. The total was down 170,000 from the year before with the number of species one less.

“The number of migratory birds visiting Korea has been on a steady decline in past years,” said Kim Jin-han of the National Institute of Biological Resources, which led the census.

The tally stood at 1.94 million in 2009 and dropped to 1.45 million in 2010 and 1.25 million in 2011.

The biggest decline was seen with the dominant species, the Baikal teal.

Its numbers tumbled by nearly 120,000, from 430,000 in 2011 to 310,000 in 2012, the data showed. Other duck species, which make up most of the migrant species visiting Korea, also dropped in numbers.

The institute explains that the declining duck numbers have been observed elsewhere in East Asia.

“The loss of habitats and insufficient food seem to be key factors behind the trend,” Kim said.

Rice fields, wetlands and coastal areas, with leftover grains, weed seeds and insects, are ideal shelters for the wintering birds to feed, rest and regain their strength, but such places are diminishing across the region, he said.

As these birds know no borders, efforts to study and protect them span territorial boundaries.

Four nations on the East Asia/Australasian Flyway ― Korea, China, Japan and Australia ― have been holding since 2008 biannual meetings of working-level government officials and private professionals. This year’s meeting was held in Songdo, Korea, earlier this month.

“Such multi-nation meetings provide a chance to better understand what happens to migratory birds on their long journey, how to stop the decline in their population, and other related problems such as the spread of avian influenza,” an official at the Korean Ministry of Environment said.

Korea has bilateral agreements on the conservation of the birds with Australia, China and is now pushing to forge another one with Japan next year.

By Lee Sun-young (milaya@heraldcorp.com)