Predicted extinctions target the planet’s most unique bird species

Jarome R. Ali, Benjamin W. Blonder, Alex L. Pigot, Joseph A. Tobias

This is a plain language summary of a Functional Ecology research article which can be found here.

White-necked Rockfowl (Picathartes gymnocephalus): a morphologically distinctive species threatened with extinction. Credit: Joe Tobias

Extinction rates are projected to increase worldwide, but it remains unclear how this loss of biodiversity might affect the way ecosystems function. Since ecological processes are hard to quantify at global scales, morphological traits can provide useful insights into species’ roles in the ecosystem. For example, the size and shape of a bird’s beak can predict the type and size of food items it consumes. We therefore examine the morphological traits of 9943 (99% of all birds) living bird species, comparing those of threatened species (according to the IUCN Red List) with those of all other birds. We quantify the total variation in beak and body shape as a measure of the diversity of ecological roles performed by birds, and we estimate how unique each species is in their combination of traits, relative to the total species pool.

A Copper-rumped Hummingbird (Amazilia tobaci). Morphological traits, such as the shape of this hummingbird’s bill, can predict the type of food a bird consumes. In the case of hummingbirds, their nectarivorous diet is evident from their bill shape (credit: Jarome R. Ali)

Our analyses show that birds with the most unique traits are the ones under most immediate threat of extinction. We also find that extinction of threatened bird species would result in unexpectedly large losses of morphological diversity. In other words, the loss of morphological diversity under projected extinctions is much larger than if species extinctions were occurring randomly. We also find evidence that this is not simply because extinction risk increases with body size, but because more specialised birds with relatively unique shapes are more highly threatened. Altogether, our results show that we risk losing many distinctive bird species to extinction along with their unique ecological roles, potentially resulting in less resilient ecosystems.

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