By Alex Kirby
BBC News Online environment correspondent
The world's largest seabirds, the albatrosses, are soon to benefit from international protection which may arrest their slide towards extinction.
Longlines are pulling albatross numbers down rapidly
South Africa has become the fifth country to ratify the international treaty on albatross protection, which will now enter into force in February.
The treaty obliges signatories to act to reduce deaths on fishing lines, which kill 100,000 albatrosses a year.
Conservationists are now urging the UK and other nations to ratify the pact.
The treaty, the Agreement on the Conservation of Albatrosses and Petrels (Acap) had already been ratified by Australia, Ecuador, New Zealand and Spain, but it needed a fifth signatory to give it force.
It requires states not only to take specific measures to reduce seabird deaths from longlining, but to draw up wide-ranging plans to tackle other threats.
These include habitat loss, marine pollution, and rats, feral cats and other introduced species at the birds' breeding sites.
BirdLife International, an alliance of conservation groups working in more than 100 countries, welcomed the South African move.
It says its research has shown longlining to be the chief culprit in the continued declines of most albatross species and related seabirds.
The practice is reckoned to kill 300,000 seabirds every year, a third of them albatrosses.
The victims die of their injuries as they try to seize bait from hooks on fishing lines up to 130 kilometres (80 miles) long, or else are dragged under water and drown.
There are 21 albatross species, all of which BirdLife says now face varying risks of extinction.
South Africa is home to significant populations of four species: the wandering, grey-headed, Indian yellow-nosed and sooty albatrosses.
Dr Euan Dunn, of the Royal Society for the Protection of Birds, BirdLife's UK partner, said: "With many albatrosses sliding towards extinction, Acap's entry into force comes not a moment too soon.
More nations need to sign up, says BirdLife
"The treaty's strength is that it is legally binding on signatory states, so they will have to take firm measures to get seabirds off the hook.
"It is now vital for the UK to ratify in time for the first meeting of the parties to the agreement in 2004, and to get its crucially important overseas territories to ratify in time too."
BirdLife wants the UK, France, Brazil, Chile and Peru to ratify the agreement promptly.
British overseas territories with large populations of some of the most threatened albatrosses include the Falkland Islands, South Georgia, and Tristan da Cunha.
Amsterdam Island, governed by France, is home to the most threatened species, the Amsterdam albatross, which is also threatened by disease.
It is now reduced to about 20 breeding pairs annually, and chick mortality is increasing.
The British sailor John Ridgway, who rowed across the North Atlantic with Chay Blyth in 1966, recently left South Africa on a year-long yacht voyage to draw attention to illegal fishing and to campaign for stricter action against it.
Images by BirdLife International