Birds Decline, Small Mammals Thrive in a Hotter World

Cactus mouse (photo by J.N. Stuart, Creative Commons license via iNaturalist)

8 March 2021

What is the future of life on Earth as the climate warms? Which species will thrive and which decline? A study published last month in Science indicates that “in a warming world, it’s better to be a small mammal than a bird.”

In the early 1900’s Joseph Grinnell made extremely detailed records of flora and fauna in California’s Mojave Desert for the Museum of Vertebrate Zoology. A century later the average temperature in the Mojave is now 2oC (3.6oF) higher. Using Grinnell’s records a team led by Eric Riddell resurveyed Grinnell’s locations to find out how birds and mammals fare in hotter, drier conditions.

If you like birds, you won’t like the news.

[In the Mojave Desert] Over the past century, occupancy of small mammals remained stable while birds severely declined.

On average, every spot surveyed had lost more than 40% of its desert bird species, such as American kestrels or mountain quail. At most sites, even the remaining species were scarcer.

Science Magazine: In a warming world it’s better to be a small mammal than a bird.
American kestrel, 2013 (photo by Cris Hamilton)

Small mammals get around the heat problem by staying underground during the day. Birds don’t have this choice and they have an additional disadvantage — their bodies use more energy to stay cool.

It looks like there will be fewer birds in a hotter world. Read more in Science Magazine: In a warming world it’s better to be a small mammal than a bird.

p.s. There is a bird who stays underground during the day and eats small mammals in the Mojave Desert: the burrowing owl.

(cactus mouse photo by J. N. Stuart via iNaturalist (CC BY-NC-ND), American kestrel photo by Cris Hamilton)

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