While they may range from tiny hummingbirds to large Indian Bustards, these birds all have one thing in common - They are all extremely rare, and either on the critically endangered or endangered/data deficient list.

In early 2010, not-for-profit publisher WILDGuides, launched a competition, challenging bird lovers to seek out the unfortunate 623 birds that had made one of these lists. Hundreds of photographers rose to the occassion, capturing all, but 79 of the 623 birds. Here are the top three winners in each category.

Critically Endangered

Winner - Kakapo (By Shane Mccinnes)

The Kakapo, which means night parrot in Maori, is a large flightless nocturnal parrot that is native to New Zealand. Also known as, an owl parrot, the bird sports a yellow-green plumage and a large gray beak. It is one of the heaviest species of parrots and the only one that cannot fly. With a lifespan of about 60 years, the Kakapo is probably one of the world's longest living birds. Despite that, this beautiful parrot, which at one time was New Zealand's third most common bird, is now critically endangered - So much so, that each of the 120 birds that are left, are known by name. One of the biggest factors that led to their demise is humans - who first hunted them down for food and then, destroyed their habitat. The last stroke came in the 1880's, when farmers released a large number of weasels and ferrets to try control the rabbit population - Unfortunately, they also fed on the Kakapo.

Runner Up - Brazillian Merganser (By Sacio Freire Bruno)

The runner-up in this unfortunate list is the Brazillian Merganser, a dark slender duck with a shiny dark green hood and a long crest. While originally found in Brazil, Paraguay and Argentina, the 250 specimens of the waterfowl believed to be left, are all clustered in Brazil. The bird's dire situation has been caused by the deterioration in their habitat, attributed to human activities like farming, construction of hydroelectric plants and tourist activities like canoeing and rafting.

Third Place - Christmas Island Frigate (By David Boyle)

David Boyle managed to snap a stunning picture of this beautiful bird in flight. Native to Christmas Island in the Indian Ocean, the Frigate does not walk or swim, instead swooping up its prey live from the beaches, the surface of the water or even stealing it from the beaks of other birds, in flight. The reason for the major decline in its population is again due to a destruction of its habitat - However, for once its not humans but, a species of ants dubbed crazy yellow ants, that got introduced to the island mistakenly and now occupy about 30% of the land. The large colonies and consumption patterns of these pesky ants has changed the island's unique self-sustaining ecosystem, which in turn, has impacted the population of this bird severely.

Endangered/Data Deficient

Winner - Asian Crested Ibis (By Quan Min Li)

The beautiful Ibis, that resembles the Flamingo used to be prevalant in Russia, Japan, South Korea and China. However, over the years, as its population has declined, it is now seen only in the Shaanxi Provincein Mainland China. In order to breed, the Ibis needs a combination of high trees for nesting and wetlands or agricultural land for feeding - the loss of which is the main reason for its woes. However, while there are believed to be only 500 left in the wild, it is a big improvement from 1981 when only seven, which included four adults, were left. Conservationists in China are trying to do everything they can to increse the population, including protecting their habitat and nests.

Runner Up - Red Crowned Crane (By Huajin Sun)

Considered a symbol of longevity and good luck in Japan and China, the Red Crowned Crane is a large, omnivorous bird whose main habitat is the large wetlands in East Asia and the freshwater marshes of China and Japan. There are currently believed to be about 2,100 birds left - 1200m in North east China and Russia and about 900 on the island of Hokkaido, in Northern Japan. While their numbers are slowly increasing, loss of habitat still remains a big issue.

Third-Place Winner - Marvellous Spatuletail (Daniel Rosengren)

In third place is this colorful white, green and bronze hummingbird, that sports blue feathers on its crest and a brilliant turquoise on its neck. The medium-sized bird that is native to Peru, has a unique feature - It has only four feathers in its tail. Loss of habitat and the fact that it is can be found only along the forest edge in Peru's Rio Utcubambaregion, have been the primary reasons for its rapid demise. However, the government is making efforts to protect and increase the population of this tiny, but stunning looking, creature.

These are just a few of the beautiful rare birds that were photographed. To view more check out more go to www.theworldsrarestbirds.com. Also, be sure to buy the book 'The World's Rarest Birds', scheduled to hit bookstores in 2012 - You will not only get a beautiful book, but also, be helping save the birds, since all proceeds will be used in conservation efforts.

Resources: world'srarestbirds.com, wikipedia.org, savingcranes.org, nationalgeographic.com