Study of 99% of all living bird species

Agami heron (Agamia agami). Credit: Joe Tobias

A new study finds that bird species with extreme or unusual combinations of traits are most at risk of extinction. The findings are published in the journal Functional ecology.

A new study led by researchers at Imperial College London shows that the most unique birds on earth are also the most endangered. The loss of these species and the unique roles they play in the environment, such as seed dispersal, pollination and predation, can have serious consequences for ecosystem functioning.

The study analyzed the extinction risk and physical characteristics (such as beak shape and wing length) of 99% of all living bird species, making it the most comprehensive study of its kind to date.

The researchers found that in simulated scenarios where all threatened and near-threatened bird species went extinct, physical (or morphological) diversity among birds would be significantly greater than in scenarios where extinctions were random.

Bird species that are both morphologically unique and endangered include the Christmas frigatebird (Fregata andrewsi), which nests only on Christmas Island, and the bristle-thigh curlew (Numenius tahitiensis), which migrates each year from its breeding grounds in Alaska to islands in the South Pacific.

The planet's most unique birds are at greater risk of extinction

Blyth’s kingfisher (Alcedo hercules). Credit: Joe Tobias

Jarome Ali, a Ph.D. candidate at Princeton University who completed the study at Imperial College London and was the study’s lead author, said: “Our study shows that extinction is most likely to prune a large proportion of the unique species from the bird tree. The loss of these unique species means a loss of the specialized roles they play in ecosystems.

“If we don’t take action to protect endangered species and prevent extinction, ecosystem functioning will be dramatically disrupted.”

In the study, the authors used a dataset of measurements collected from live birds and museum specimens, a total of 9943 bird species. The measurements include physical features such as the size and shape of the beak and the length of wings, tails and legs.

The authors combined the morphological data with extinction risk, based on the current threat status of each species on the IUCN Red List. They then ran simulations about what would happen if the most endangered birds became extinct.

The planet's most unique birds are at greater risk of extinction

Bristle Thigh Curlew (Numenius tahitiensis). Credit: Joe Tobias

While the dataset used in the study was able to show that the most unique birds were also classified as endangered on the Red List, it failed to show what links bird uniqueness to risk of extinction.

Jarome Ali said: “One possibility is that highly specialized organisms are less able to adapt to a changing environment, in which case human influences could directly threaten species with the most unusual ecological roles. More research is needed to dig deeper into to go into the connection between unique traits and extinction risk.”

More information:
Jarome Ali et al, Bird extinction threatens to cause a disproportionate reduction in functional diversity and uniqueness, Functional ecology (2022). DOI: 10.1111/1365-2435.14201

Offered by British Ecological Society

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