The satellite tracking project conducted by the bureau in collaboration with Taiwan's top academic institution Academia Sinica and the nongovernmental organization Raptor Research Group of Taiwan is a major breakthrough which exposes the whole migration route of the rare birds, also known as the Butastur indicus, the official said.

In an attempt to unveil the previously unknown route, Japan spearheaded several years ago a similar study to track the bird species's migration, but only caught pictures of some of the population wintering in the country, according to the official.

The bird is a species listed in the Convention on International Trade in Endangered Species of Wildlife Fauna and Flora (CITES) as a protected species and is also classified as a rare and valuable species under the Wildlife Conservation Law, according to the official.

About 15,000-35,000 of the migratory birds stop over at Taiwan on their north-south migration every spring and fall.

The migration areas of the bird species are limited to the east and south parts of Asia.

In summer, the species breeds in the eastern part of Asia, including northeastern China, the Korean Peninsula, and the southeastern part of the Ussuri River of Russia, and Japan.

In autumn, the birds migrate south to southern China, the Indochinese Peninsula, the Philippines, Borneo, Sulawesi and New Guinea to spend the winter. A few of them spend their winter on Ishigaki Island in Japan, according to the official.

Last year, the number of the hawks recorded to have passed through Taiwan reached 43,516, a record high in the past 20 years, the official noted.

Among them, three which had been implanted with satellite tracers were released on Oct.12, 2008 at Kenting town in southern Taiwan by a research team led by Liou Siao-ru, chief of the Raptor Research Group of Taiwan, and were tracked the next day in the Philippines, according to the official.

One of the three birds, nicknamed Cape No. 2, returned to central Taiwan on March 21 and then reached Zhejiang Province in eastern China on March 25, the official said.

He said once the bird returns to its habitat expected at the end of April, the bureau will hold a presentation to make public the results of the project.

The other two of the three birds, nicknamed Cape No. 1 and Cape No. 3, are in Manila and Mindoro in the Philippines and are moving northward to return to Taiwan, the official said, citing the latest data.

(By Y.L. Kao)