Endangered black-faced spoonbills that spend the winter in wetland areas of Greater Tainan are making their return migration to northeast Asia nearly one month later than usual, researchers at Taijiang National Park said on Tuesday.
The researchers said the delayed migration might have been caused by climate change and they estimated that about 200 of the birds had already left Taiwan.
The movements of one of two birds being tracked by the park with wireless radio transmitters since last month are no longer detectable, indicating that the bird has already left Taiwan, the researchers said.
Other changes in the birds’ behavior have also been noted by researchers.
The number of birds arriving in Taiwan peaked in January rather than between the end of November and the middle of December, as observed in previous years. In addition, the birds began moulting into their breeding plumage slightly later than usual, the researchers said.
A month earlier, researchers had predicted that the slow growth of the breeding plumage would delay the migration season, as only 40 percent of the birds had begun growing new feathers at that time. The new feathers normally finish growing by the middle of March.
The birds began migrating from South Korea to Taiwan at about the same time as in previous years — around the time of the Mid--Autumn Festival, which fell on Sept. 12 last year — but the numbers did not peak until about a month later than normal.
The wading bird has a worldwide population of about 2,000 and it winters mostly in Taiwan, Hong Kong and Vietnam.