Ubiquitous marshes and ponds in the Kuantu Nature Reserve in Taipei create an idyllic scene. In early spring as winter draws to a close, birds flit among the gentle waves, as if right out of a poem or picture. (Peng Chun-fu)

Kuantu, this northern wetland where the Keelung River empties into the Tanshui Estuary, is an important stop for East Asian migratory birds on their spring and autumn journeys, and a place where many migrants spend the winter, waiting for the warmth of spring to change into their beautiful summer plumage and set off back north to breed.

According to Wild Bird Federation Taiwan, more than 250 bird species have been recorded at Kuantu, almost half the birds known in Taiwan. What charms does this marshy area possess, to attract so many waterbirds to linger here?

From the air we see that Kuantu, in northwestern Taiwan, is flanked to the northeast by the tall mountains of the Mt. Tatun group, and to the west by Mt. Kuan-yin and the Linkou plateau. These two massive windbreaks shield Kuantu from the force of the northeasterly monsoon.

On making landfall at the Tanshui Estuary, clever birds discover that although the beaches at Watsaiwei offer plenty of food, vegetation is sparse and they are exposed to the wild buffets of the north wind. The less hardy among them scout their way upriver until they come to the wetlands of Kuantu. Here they can shelter from the wind and cold and find a range of vegetation to roost in, and there is no lack of food. This makes Kuantu a prime choice as a place to replenish their energy before they spread their wings and continue on their way.

If you enter at the sluice gates in front of Kuantu Temple and set out along the Keelung River embankment, the 100-plus-hectare Kuantu wetland stretches out before your eyes. The large patch of luxuriant mangrove forest to the right, outside the embankment, is the Kuantu Nature Reserve, while the wetland area to the left, with its high and low tussocks of grass and pools large and small, is Kuantu Nature Park, which opened in late 2003.

However, 30-odd years ago, to both sides where the embankment now runs was an expanse of abandoned farmland that had become a marsh filled with reeds and sedges. Earlier still it was farmland made up of paddy fields. If we turn back the clock even further to 1697, when Yu Yonghe came to Taiwan to mine sulfur, as his boat sailed up the Tanshui River, flanked by mountains, on arriving at Kuantu he was amazed to see a huge lake--the fabled Taipei Lake!

The varied fortunes of Kuantu over the last three centuries and more tell of the changing ecology of the waters here. After the Kuantu narrows were dynamited in the 1960s to broaden the river by 100 meters, the tides brought seawater flowing into this riverside wetland a full ten kilometers from the river mouth. With the saltwater came the mangrove species Kandelia obovata, which replaced the grassy marsh outside the embankment. Thus a diverse wetland environment came into being, with saltwater, brackish and freshwater areas.