Dozens of newly-recognised bird species have been listed as threatened with extinction, a new report has revealed.
A review of the classification of "non-passerine" birds such as birds of prey, seabirds, waterbirds and owls has recognised 361 new species which were previously not treated as separate species.
The assessment by Birdlife International for the International Union for Conservation of Nature (IUCN) Red List of threatened species revealed that more than a quarter of the new birds are at risk of extinction, compared to 13% of all bird species.
This means they are urgent priorities for conservation, wildlife organisation Birdlife said.
The new species lift the total number of non-passerine bird species to 4,472, revealing that almost a tenth of the world's bird species have been "flying below the conservation radar", experts said.
New species such as the Belem carassow from Brazil and Desertas petrel from Madeira have been listed as globally threatened.
But for the blue-bearded helmetcrest, a hummingbird from Colombia, it may be too late for conservation action, as it has not been seen for nearly 70 years.
Until the new assessment, only one species of ostrich had been recognised and was not considered to be threatened with extinction.
Now the Somali ostrich, found in Somalia, Ethiopia, Djibouti and Kenya, has been recognised as a distinct species and listed as vulnerable to extinction, as its population is thought to be in rapid decline due to hunting, egg-collecting and persecution.
Jane Smart, global director of the IUCN biodiversity conservation group said: "Thanks to the ongoing assessment work of Birdlife, the early recognition of those threatened species such as the Somali ostrich should result in timely targeted action to safeguard the species and protect important sites."
In addition to assessing newly recognised species, the 2014 Red List re-assessed existing birds, such as the Bugun Liocichla, known only from three areas of the Himalayas, which has been re-classified as critically endangered, the highest level of threat.
The new assessment also highlights several threatened bird hotspots, where many of the new species were identified, such as parts of South East Asia.
The experts raised concerns about the Indonesian island of Java, where the Javan flameback, a type of woodpecker, has been newly-recognised and classified as vulnerable to extinction and the new Javan blue-banded kingfisher has been classed as critically-endangered.
The island has many distinct species, but high human population and increasing rates of development are threatening the birds with extinction, the experts said.
Dr Stuart Butchart, Birdlife's head of science, said: "The IUCN Red List is crucial not only for helping to identify those species needing targeted recovery efforts, but also for focusing the conservation agenda by identifying the key sites and habitats that need to be saved, including important bird and biodiversity areas.
"The updated 2014 Red List for birds will help set future conservation and funding priorities."