Earth’s Most Unique Birds Face the Greatest Danger of Extinction

According to recent research, bird species with extreme or rare combinations of traits face the greatest danger of extinction. 

According to a new study performed by Imperial College London scientists, the most unique birds on the globe are also the most endangered. The extinction of these species and the unique roles they serve in the environment, such as seed dispersal, pollination, and predation, might have serious consequences for the functioning of ecosystems. 

The study, which is the most comprehensive of its type to date, examined the extinction risk and physical features (such as wing length and beak shape) of 99% of all extant bird species.

Bristle-thighed Curlew (Numenius tahitiensis). Credit: Joe Tobias

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

Bird species that are both morphologically unique and threatened include the Christmas Frigatebird (Fregata andrewsi), which nests only on Christmas Island, and the Bristle-thighed Curlew (Numenius tahitiensis), which migrates from its breeding grounds in Alaska to South Pacific islands every year.

Jarome Ali, a Ph.D. candidate at Princeton University who completed the research at Imperial College London and was the lead author of the research, said: “Our study shows that extinctions will most likely prune a large proportion of unique species from the avian tree. Losing these unique species will mean a loss of the specialized roles that they play in ecosystems.

Agami Heron (Agamia agami). Credit: Joe Tobias

“If we do not take action to protect threatened species and avert extinctions, the functioning of ecosystems will be dramatically disrupted.”

In the study, the authors used a dataset of measurements collected from living birds and museum specimens, totaling 9943 bird species. The measurements included physical traits like beak size and shape, and the length of wings, tails, and legs.

The authors combined the morphological data with extinction risk, based on each species’ current threat status on the IUCN Red List. They then ran simulations on what would happen if the most threatened birds were to go extinct.

Although the dataset used in the study was able to show that the most unique birds were also classified as threatened on the Red List, it was unable to show what links uniqueness in birds to extinction risk.

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

Reference: “Bird extinctions threaten to cause disproportionate reductions of functional diversity and uniqueness” by Jarome R. Ali, Benjamin W. Blonder, Alex L. Pigot and Joseph A. Tobias, 23 November 2022, Functional Ecology.
DOI: 10.1111/1365-2435.14201

The study was funded by the UK Natural Environment Research Council.