Asian Crested Ibis
Launched in 2010, the competition ranked pictures of birds that fall into three categories determined by the International Union for Conservation of Nature: endangered or data deficient, critically endangered or extinct in the wild, and critically endangered migratory species.
The above shot took top honors in the "endangered or data deficient" category. The Asian crested ibis once thrived in Russia, Japan, and China, but its population has shrunk to about 250 in China's Shaanxi Province. Agricultural activities have probably affected the bird by reducing available feeding grounds, according to the World's Rarest Birds website.
A panel of five independent judges—including two wildlife photographers, a wildlife artist, a citizen interested in birds, and a book editor—rated the entries on image quality, subject rarity, and aesthetics. Winning images will be featured in the book The World’s Rarest Birds, to be published in 2012 by WILDGuides.
The book's "key message is poignant—a large proportion of the world's birds, including every one depicted, is threatened with extinction," Andy Swash, managing director of WILDGuides, said in a statement.
Two endangered scaly-sided mergansers glide across the water in a picture that won fifth place in the "endangered or data deficient" category.
Habitat loss and illegal hunting have reduced the bird's population to about 2,500 individuals in Russia and China, according to the nonprofit BirdLife International.
Overall, the competition received photos that represent 90 percent of the 566 rarest bird species.
The species lives in a severely fragmented forest habitat that continues to be destroyed, according to the nonprofit BirdLife International.
Named a second place winner in the "endangered or data-deficient" category, the above picture shows a red-crowned crane making a courtship display.
Though the bird's population is stable in Japan, the mainland Asian population is declining due to habitat loss and degradation of wetlands for agriculture and development, according to BirdLife International.
This "touching image" of two orange-bellied parrots won the category for critically endangered migrating birds, according to a World's Rarest Birds contest statement.
The small parrot breeds only in southwestern Tasmania (see map) and migrates to southeastern Australia in the winter, where agriculture and development are crowding out its habitat. Probably fewer than 150 animals remain in the wild, according to BirdLife International.
One of the rarest birds of all is New Zealand's kakapo. The above picture of the large, flightless bird approaching the camera snagged first place in the "critically endangered or extinct in the wild" category.
Only 124 animals remain in the wild—the species has been largely wiped out by introduced predatory mammals such as feral cats.
A photograph of a Honduran emerald perched on a branch earned fifth place in the "critically endangered or extinct in the wild" category.
Found only in Honduras, the hummingbird exists in an "extremely small and severely fragmented range," which is declining due to habitat loss, according to BirdLife International.
Habitat loss, cat predation, and drought have contributed to the species' ongoing decline in its native Hawaii. The bird's numbers are expected to plummet by 97 percent over the next 14 years, according to BirdLife International.
Christmas Island Frigatebird
A picture of a Christmas Island frigatebird flying over the Indian Ocean snagged third place in the "critically endangered or extinct in the wild" category.
A "captivating" photo of a Brazilian merganser and her ducklings won second prize in the "critically endangered or extinct in the wild" category, according to a World's Rarest Birds contest statement.
In a sign of hope for the species, recent data from Brazil suggest that the merganser's status is better than previously thought, according to BirdLife International.
Great Indian Bustard
A shot of the Great Indian bustard in mid-flight snagged fourth place in the "endangered or data deficient" category.
Widespread hunting for sport and food in India is driving the bird to extinction, according to BirdLife International.
A "stunning" hummingbird restricted to just two sites, the bird's population is estimated to be less than a thousand, and it's decreasing due to deforestation for cash crops such as marijuana and coffee, according to a World's Rarest Birds contest statement.