ROME (Reuters) - Birdwatchers the world over, here’s a challenge for you.

The slender-billed curlew is seen at its wintering site of Merja Zerga, Morocco, in a February 1995 photo. REUTERS/Chris Gomersall/Royal Society for the Protection of Birds/Handout

Conservationists launched a global quest on Thursday for the slender-billed curlew, the rarest bird in Europe, North Africa and the Middle East, which was last spotted in Oman in 1999.

They want birdwatchers to help find out whether the bird still exists -- and are handing out a toolkit complete with pictures, a map of the most recent sightings and a recording of the bird’s call to make identification easier.

“This is the Holy Grail of birdwatching. We need to find it before it’s too late to save it,” said Nicola Crockford of Britain’s Royal Society for the Protection of Birds, one of the main conservation groups behind the campaign.

“Next winter we will have the first ever comprehensive international survey to find the bird -- it will stretch all the way from Morocco right the way through to Iran, the Mediterranean, the Red Sea and the Middle East,” she told Reuters in an interview.

Besides deploying an army of professional bird counters to the wetlands where the bird may still survive, Crockford is asking volunteer birdwatchers to join the search -- and is even thinking of offering a reward.

“It is just possible that small numbers of the bird may still be wintering in an isolated part of North Africa or the Middle East, or that some unknown nesting site may be discovered in the depths of central Asia,” she said.

The crow-sized bird, also known as Numenius tenuirostris, used to be seen regularly and in large flocks -- it was regarded as very common in some areas of the Mediterranean. Its only known breeding ground is in Siberia.

But its population declined dramatically during the 20th century because of hunting and loss of its wetland habitat. It could be now numbering lower than 50, if it is not extinct altogether.

The most recent verified sightings are of one to three birds, compared to flocks of over 100 birds in the 1960s and 1970s.

DON’T FORGET THE RINGTONE

The bird’s bill has a fine, sharp tip and is characteristically slender and much narrower than that of the Eurasian curlew. Adults have dark, brownish spots rather than streaks on pale breasts.

The slender-billed curlew is also known for its unusual migratory patterns, going east-west rather than north-south, and preferring to fly inland rather than on the coast.

It is considered a relatively tame bird, which may explain why it has been decimated by hunters and tends to feed higher up the wetland shore than other birds.

Conservationists hope that if surviving specimen are found, they can put satellite tags on them and follow them through their migration. That is why the campaign is being launched in the winter, when birds tend to stay in the same place for long enough making it is easier to track them down.

Crockford says birdwatchers wanting to help should do what she did -- download the only recorded call from the bird on their mobile phone so they can become familiar with it.

That call, which can be found on www.slenderbilledcurlew.net, came from a bird recovering from a shooting wound in Morocco in January 1990.

“People should have it as their ring tone...and then this call will become enshrined in their minds and when they are out in the field they will think ‘Ah, the slender-billed curlew’ or ‘my mobile phone’.”