The world's 100 most endangered and unique birds have been ranked in a newly published study, and the list includes a corpse-eater with legendary skills of decapitation, a shameless self-inflator, and the world’s heftiest parrot. Conducted by a team from Yale University, Simon Fraser University, and the Zoological Society of London, the study analyses where the 9,993 recognised species of birds in the world live; how many relatives they have (very few means better evolutionary distinctness); and how at risk they are in their environment.

Published in the latest edition of Current Biology, the study is the first of its kind, and highlights the species we should be focusing our conservation efforts on the most. “We … found that if we prioritise threatened birds by their distinctness, we actually preserve very close to the maximum possible amount of evolution,” said one of the team, biologist Arne Mooers from Simon Fraser University in Canada. “This means our method can identify those species we cannot afford to lose and it can be used to preserve the information content represented by all species into the future. Both are major goals for conservation biology.”

Here are the top 10 birds on the list:

1. Giant ibis

Far more majestic than its smaller, garbage-diving relatives, the giant ibis (Thaumatibis gigantea) has been declared the most endangered and evolutionarily distinctive bird in the world. Native to the marshes, wide rivers, and seasonal water meadows of northern Cambodia, with a few individuals hiding out in southern Laos and perhaps Vietnam, these are some huge birds. They stand around a metre tall and weigh over 4 kg, and carry a dusty brown hue across their plumage and exposed skin. Next to nothing is known about their breeding habits, and it’s estimated that just over 100 breeding pairs are left in the wild. Relentless deforestation, droughts, and hunting have together contributed to this species’ rapid decline.

2. New Caledonian owlet-nightjar

By far the most elusive species of bird in the world, the New Caledonian owlet-nightjar (Aegotheles savesi) has not been seen alive since 1998. The species is found only in the humid forests of New Caledonia - a little archipelago 1,210 km to the east of Australia - and is known from just two preserved specimens. One of these was the first New Caledonian owlet-nightjar ever found, and was identified when it flew into someone’s window in 1880. The other specimen is dated to 1915. A couple of expeditions to New Caledonia in 2002 and 2007 failed to produce a single sighting. It's thought there are between 1 and 49 adults left in the wild.

3. California condor

If you're caught one too many times knee-deep in the carrion you're currently enjoying as your lunch, you're pretty much guaranteed to find yourself the subject of some kind of horrific mythology. The Native American tribes of California held several beliefs about the California condor, none more literally blood-soaked than that of the Mono people of the central Sierra Nevada Mountains, the Eastern Sierra, and the Mono Basin. According to legend, the California condor would seize humans, cut off their heads, and drain their blood in order to flood the home of a figure known simply as the Ground Squirrel. The Condor would grab the Ground Squirrel as he fled from his burrow, but as he lowered his head to drink his victim's blood, the Ground Squirrel would cut off the Condor's head. It was also believed that by wearing their feathers, the 'money finders' of the Mono tribe could inherit the California condor's keen eyesight to help them seek out lost valuables.

Nowadays, the California condor's decline has been pinned to its low output of offspring, poaching, lead poisoning, and habitat destruction. According to a study published in 2012, the leading cause of mortality in young condors is eating trash fed to them by their parents.

4. Kakapo

I could tell you about the gorgeous and endangered kakapo (Strigops habroptilus) from New Zealand, but why would I, when I could get Stephen Fry to do a much more charming job of it himself.

"Look, he's so happy":

5. Kagu

Something tells me, just by looking at it, that this incredibly elegant bird wouldn't be caught dead ripping people's heads off or trying to mate with them. Known locally in its native New Caledonia as 'the ghost of the forest', the ash-white, almost flightless kagu (Rhynochetos jubatus) is the only living representative of the entire Rhynochetidae clade. While the largest island of the New Caledonian archipelago, Grand Terre, has adopted the heron-like bird as its national emblem, that hasn't stopped its introduced dogs, cats, and pigs from relentlessly picking them off. Habitat loss has also led to the species' steep decline over the last 20 years.

6. Bengal florican

Native to the grasslands and open forest of Cambodia, the Bengal florican (Houbaropsis bengalensis) can also be found thousands of kilometres away in a second tiny population along the base of the Himalayas. It's thought that there are currently fewer than 1,000 adults left in the wild, so the Cambodian government has established six Bengal Florican Conservation Areas in order to protect 173 square kilometres of breeding habitat in the grasslands and 138 square kilometres of open forest. They've also been working on awareness programs for local communities, which will hopefully see a reduction in poaching. A number of farmers living close to the conservation areas have joined a wildlife-friendly farming scheme as part of the program.

7. Forest owlet

Don't be fooled - this stocky little bird might look docile, but you wouldn't want to get in its way when it's hungry. The forest owlet (Heteroglaux blewitti) wields ridiculously huge talons, which it uses to snare prey animals up to twice its own size. The critically endangered species has been reduced to a tiny, fragmented population in central India, which remains threatened by the ongoing loss of deciduous forest in the area. For over a century, the species was assumed to be extinct, until it was rediscovered in 1997 in Maharashtra by American ornithologist, Pamela Rasmussen. The population is estimated at between 70 and 400 individuals. Read about how scientific fraud almost led to this tiny owl’s extinction.

8. Philippine eagle

With its shaggy bronze mane and proud white chest, the Philippine eagle (Pithecophaga jefferyi) is about as magestic as a bird can get. Capable of growing to more than a metre long and 8 kg in weight, this stunning creature is the largest eagle in the world, in terms of length. Found only in the Philippines, it was was originally named the 'monkey-eating eagle', thanks to an assumption that it preyed exclusively on primates. Later studies confirmed that monkeys, and pretty much everything else was fair game, from civets and hornbills to large snakes and monitor lizards.

One of the big hurdles in conserving the Philippine eagle is that each breeding pair requires a range up to 40 square kilometres to adequately feed and rear their offspring, which makes it particularly vulnerable to deforestation. It's thought that the wild population currently stands at around 180 to 500 mature adults.

9. Christmas Island frigatebird

Maybe I've been playing too much Dark Souls, but if someone approached me with a swollen skin-balloon anchored to their throat and chest area, my first move would be to reach for my Havel and Antiquated armour sets and brace myself for a heavy bout of cursing cloud. But I'm clearly not a frigatebird, so what would I know. Also, ladies, the Christmas Island frigatebird (Fregata andrewsi) can do other things besides very conspicuous self-inflation. It happens to belong to the Fregatidae family of birds that boast the largest wingspan to body weight ratio in the world, which means it can stay happily aloft for more than a week at a time without rest. It's also pretty great at performing kleptoparasitism, which means stealing food from other birds, so that's something.

This critically endangered native Australian species is currently sitting at an estimate of 2400 to 4800 adults left in the wild.

10. Sumatran ground-cuckoo (Carpococcyx viridis)

This striking little forest-dweller hails from the thick, humid rainforests of southern Sumatra. It keeps to the forest floor, where its dull green, brown, and black plumage works as fantastic camouflage, unlike the bright ring of turquoise, blue and magenta that orbits its eyes. It's known from just eight specimens, and it's thought that there are just 70 to 400 individuals left in the wild.

In 2007, its call was recorded for the first time, its song resembling something of an awkward "double squark".

View the list of 100 most distinctive and endangered species here.

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