The Big Bird Race marks 30 years of raising funds for Mai Po wetlands

With the high-rises of Yuen Long and Tin Shui Wai to the south, Fairview Park estate to the southwest and the urban sprawl of Shenzhen fringing the northern coast, Deep Bay may seem an unlikely location for one of the world's greatest wetland reserves. Yet on the southern shore lies the grandly titled Mai Po Marshes Wildlife Education Centre and Nature Reserve, often known simply as Mai Po.

The reserve covers an area of 380 hectares: 20 times the size of Victoria Park. Most of it is former shrimp ponds, now jointly managed by the Agriculture, Fisheries and Conservation Department and the WWF Hong Kong, although it's the latter that does the hands-on work. And it is the only member of WWF's global network to manage a reserve.

Mai Po is also the beneficiary of Hong Kong's oldest annual fundraiser - the Big Bird Race, which marks its 30th anniversary this year. The event was instigated with the help of Mary Hotung Ketterer, then honorary director of WWF Hong Kong, to raise funds for the conservation and management of Mai Po. It was based on a British bird race, in which teams spent a day dashing about to spot as many species as possible. From just two teams when first held in 1984, the local race grew quickly, attracting more teams and sponsors, and becoming a key way for WWF Hong Kong to obtain funds to buy rights to manage more ponds. This later provided crucial support for habitat management.

Deep Bay is really a shallow estuary, which formed about 6,000 years ago as the Ice Age ended and the rising sea inundated a river valley. Silt carried in by streams and rivers formed mudflats along the shorelines, and from the 13th century man began reclaiming areas of land. Reclamation efforts accelerated in the last century, especially as farmers built bunds with sluice gates to impound areas of mudflats. They grew salt-tolerant red rice on the new, marshy land.

The farmers occasionally irrigated their paddies with water from the bay, and as the water came in, so too did shrimp, which were harvested by the farmers. This gave rise to commercial shrimp farming during the Japanese occupation in the early 1940s, and at places including Mai Po new ponds were created specially to cultivate shrimps.

These ponds, called gei wai, were mainly shallow, and the farmers retained mangroves. This made the ponds attractive to a host of waterbirds, such as herons, ducks and cormorants.