Bird extinction means that all members of a bird species are no longer alive. Of the about 11,154 known bird species, 159 (1.4%) are extinct, and 226 (2%) are critically endangered. Most scientists agree that if human activities continue as they are now, about one-third of all bird species, and even more bird populations, could become extinct by the end of the 21st century. For critically endangered species, scientists believe they may go extinct within a few decades without conservation efforts. For some of these species, it is unclear whether any living members still exist.
Causes
Habitat loss, exploitation, and invasive species are the main causes of bird extinction. Island birds are especially affected, as 95% of all bird extinctions since the late 15th century were species that lived only on islands. Habitat loss greatly harms birds, with deforestation linked to declines in about 70% of known bird species. Some birds are more affected by human activities because of their size. Smaller birds are often harmed more by habitat destruction, while larger birds are more likely to be endangered by hunting or invasive species. Many large birds facing extinction are island species, and these differences may be connected to traits that differ between island and mainland birds.
Even partial habitat loss, such as when forests are broken into smaller pieces, can harm birds and lead to extinction. For example, the wood thrush, which is not currently endangered, has declined in numbers partly because its habitat is fragmented. The brown-headed cowbird, a bird that lays its eggs in other birds’ nests, is more common in smaller forest areas. This change in habitat has made woodland birds like the wood thrush more vulnerable to parasitism, which reduces their populations.
Exploitation, such as collecting eggs or hunting birds for feathers, meat, or taxidermy, also causes extinction and population declines. While these activities are not always harmful to wildlife, overharvesting can severely damage bird populations, leading to local extinction or total extinction. Although often linked to the past, bird exploitation still happens today, even with laws meant to protect wildlife. For example, the ortolan bunting, a songbird considered a traditional delicacy, is hunted illegally in France, risking its complete extinction. The pet trade also harms birds, especially parrots. This poaching was the main reason the Spix’s macaw went extinct in the wild.
Invasive species, such as pigs and rodents, can threaten bird survival, especially birds with limited ranges, like island species. These invasive animals often attack birds on the ground, which many island birds are not used to or cannot defend against. The kākāpō, a critically endangered parrot in New Zealand, relies on hiding and staying still to avoid predators. This behavior works against native birds of prey but does not protect the kākāpō from invasive mammals like rats, cats, and stoats.
Many bird extinctions linked to disease are also connected to invasive species. Hawaiian honeycreepers, a group of finches native to Hawaii, are harmed by avian malaria. The spread of this disease to honeycreepers is tied to the arrival of the invasive southern house mosquito, which carries the malaria parasite.
Notable examples
The dodo is one of the most well-known extinct bird species. This large, flightless bird, closely related to doves, lived only on the island of Mauritius in the Indian Ocean. Because they had no natural predators and plenty of food, the dodos changed over time to fit their environment. They were much larger and heavier than other doves. The Dutch claimed Mauritius around the year 1400, and explorers often wrote about the dodo. Dodos were easy to catch and had a lot of meat, so sailors hunted them for food. Although hunting likely contributed to their decline, introduced animals, such as pigs, probably played a major role in their extinction. Pigs reproduced quickly and may have harmed dodo young or competed with adult dodos for resources. Due to habitat loss and invasive species, the dodo is believed to have gone extinct by the late 1600s, before scientists fully described them. Their sudden disappearance shows how vulnerable island species can be, and the dodo is an early example of a species lost because of human actions.
The great auk, also called the "Penguin of the North," was a flightless bird that lived in the North Atlantic Ocean and nearby islands. It once lived as far south as the United States and Europe, but by the 1800s, it only bred on a few rocky islands. People hunted great auks for their valuable feathers, eggs, and soft down. It was easier to hunt them during their breeding season, when they gathered in large groups on islands. Outside of this time, they were harder to find because they spent most of their time in cold ocean waters, where they swam quickly. The last known great auk was seen in 1844, when a pair was killed by fishermen who wanted to sell their feathers. Scientists believe the species became extinct around this time.
The passenger pigeon was a bird that once lived in large groups across North America. Before European settlers arrived, passenger pigeons may have made up as much as 40% of all birds in the region. The main reasons for their extinction were habitat loss and overhunting. People also cut down forests, which harmed the birds, and an invasive disease called chestnut blight reduced the number of chestnut trees they relied on. Because passenger pigeons lived in large flocks, people thought they were too numerous to need protection. They were hunted in large numbers, and a meat industry based on passenger pigeons developed. Some laws were created to help protect them, but these did not stop their decline. Their habit of nesting together made it hard to breed them in captivity, and their numbers continued to drop. The last passenger pigeon, named Martha, died in 1914 at the Cincinnati Zoo, 20 years after the species disappeared from the wild. Scientists have studied the passenger pigeon's complete genetic code and are exploring ways to bring the species back using advanced technology.
Also known as the Carolina parrot or Carolina conure, the Carolina parakeet lived in the eastern part of the United States. These birds ate a lot of seeds from crops, which upset local farmers. People also hunted them for their bright feathers. These two factors caused many birds to be killed, and their habitat was lost. The Carolina parakeet was declared extinct in the early 1920s. The last known member of the species, a male named Incas, died in the Cincinnati Zoo in 1918.
The Tasmanian emu was a type of emu that lived only on the island of Tasmania in Australia. Compared to emus on the mainland, Tasmanian emus were smaller and had darker feathers, but they did not have the black feathers that other emus had. Historical records show that the Tasmanian emu became extinct in less than 20 years, from the 1830s to the 1850s. This happened because of several factors that caused the subspecies to disappear.
By region
In June 2020, the Royal Society of South Australia released a list of 95 Australian bird fossils. The list includes three species of large flamingos from the Kati Thanda-Lake Eyre and Lake Frome areas in South Australia. These flamingos lived in the area for about 25 million years before becoming extinct around 140,000 years ago, likely due to drought. The list also includes penguins that were about 2 meters (6 feet 7 inches) tall. These penguins lived between about 60 million and 30 million years ago and became extinct during the Oligocene period. Researcher Trevor Worthy noted that scientists know little about how birds evolved in Australia, which has about 1,000 bird species today.