The great slaty woodpecker is not the most attractive of birds, with its bald head and grey cloak of feathers.

But a rare sighting near the summit of Bukit Timah Nature Reserve last week has got the birding community in Singapore buzzing with excitement.

The reappearance of the woodpecker, thought to be extinct in Singapore due to forest clearance during the Republic's developing years, has been described by veteran birdwatcher Alan OwYong as the greatest ornithological event in Singapore in the last decade.

"Since 1950, the great slaty woodpecker, the largest woodpecker in the world, has disappeared from our forests along with seven other woodpecker species," Mr OwYong, committee member of the Nature Society's (Singapore) Bird Group, told The Straits Times.

"Its reappearance a few days ago was most unexpected, as it is the rarest among the eight species."

Sighting shows value of forests

The bird was first spotted by nature photographer Ted Lee at 2.15pm last Wednesday. It had been perched high up in a tree near the summit of the reserve, Mr Lee said. "I was photographing another bird when I heard the great slaty calling from another tree. So I snapped some shots of it," said the 60-year-old retired engineer.

UNLIKELY TO BE LOCAL It's a species that has gone locally extinct, and it's unlikely that an individual has been hiding in Singapore for this long without being discovered. NATIONAL UNIVERSITY OF SINGAPORE BIRD SCIENTIST DAVID TAN, who caught a glimpse of the great slaty woodpecker at the weekend and described it as one of the most spectacular sightings here this year.

UNEXPECTED SIGHTING Since 1950, the great slaty woodpecker, the largest woodpecker in the world, has disappeared from our forests along with seven other woodpecker species. Its reappearance a few days ago was most unexpected, as it is the rarest among the eight species. MR ALAN OWYONG, committee member of the Nature Society's (Singapore) Bird Group.

LOSS TO THE NATION Although these species can be found in Malaysia, they represent a loss to Singapore as a nation, in terms of biological diversity and natural heritage. DR YONG DING LI, of conservation group BirdLife International, referring to at least eight species of woodpeckers, excluding the great slaty, that Singapore has lost since the 1890s.

At that time, he had no idea about the significance of his discovery. He had never seen the bird before, and could not immediately identify it. But it had a unique colouration.

Later that evening, he posted the photograph he took on a Facebook group called Bird Sightings. The bird was quickly identified by other members as the great slaty woodpecker.

Birdwatchers and nature photographers visited Bukit Timah Nature Reserve on subsequent days in the hope of spotting the woodpecker.

Mr OwYong said it was likely that the woodpecker had flown in from Malaysia. A check by The Straits Times showed that the Jurong Bird Park does not have this species.

While the sighting was encouraging, bird scientists say it remains to be seen if the great slaty woodpecker could take the Oriental pied hornbill's place as the poster animal of Singapore's greening efforts.

The hornbill was extinct in Singapore for nearly a century before recolonising in Pulau Ubin in the early 1990s. An extensive reintroduction programme by the National Parks Board also helped bring the bird's numbers back, and they can now be seen in many places across mainland Singapore.

National University of Singapore bird scientist David Tan, who caught a glimpse of the great slaty woodpecker at the weekend, called it one of the most spectacular sightings in Singapore this year.

He said: "It's a species that has gone locally extinct, and it's unlikely that an individual has been hiding in Singapore for this long without being discovered."

Dr Yong Ding Li of conservation group BirdLife International said another bird thought to have gone extinct, the buff-rumped woodpecker, was also "back from the dead". He spotted it in MacRitchie Forest in 2012, and other birdwatchers have seen it since.

The rediscoveries show that Singapore's forests, though fragmented, still have considerable value. They may harbour previously overlooked species like the buff-rumped woodpecker, and the reappearance of the great slaty also shows that forests here may be used by birds dispersing from the increasingly disturbed forests of neighbouring countries, Dr Yong said.

But while the recent rediscoveries are encouraging, he said Singapore's forest habitats are still under threat from development. The upcoming Cross Island MRT Line, for example, could potentially tunnel under the Central Catchment Nature Reserve.

Singapore has lost at least eight species of woodpeckers, excluding the great slaty, since the 1890s.

Dr Yong added: "Although these species can be found in Malaysia, they represent a loss to Singapore as a nation, in terms of biological diversity and natural heritage."