The Cassia Crossbill: It’s Looking Grim

Cassia Crossbill, South Hills, Idaho

The Cassia Crossbill, Idaho’s sole endemic species, is found only in the South Hills and Albion Mountains, south of Twin Falls, Idaho. Its range is limited to about 70 square kilometers – a little over 170,000 acres, all in the Rocky Mountains Lodgepole Pine forests. As WC writes this post, more than 100,000 acres of that range has been burned by the Badger Fire, an as yet uncontrolled wildfire.

Here’s the InciWeb maps as of September 20, 2020 at 8:00 AM

InciWeb Fire Map, Badger Fire, September 20

According to the Forest Service, high winds and critically dry fuels resulted in extreme fire behavior, including long range spotting and fire whorls, all of which caused the fire to grow rapidly.

Here’s an eBird map showing where the Cassia Crossbill has been spotted in the South Hills.

Cassia Crossbill range map, via eBird

You can see that half or more of the Cassia Crossbill’s South Hills range has been destroyed by the Badger Fire. Now it’s true that lodgepole pines have evolved with wildfire. But a fire this hot burns the cones on the ground, the source of seeds to revegetate the burned areas.

And for the birds, it’s just not possible to wait on lunch until the trees grow back.

Maybe the fire can be kept out of the western half of the South Hills, preserving some of the habitat, and maybe that will sufficient range to preserve the species. Maybe the smaller population in the adjoining Albion Mountains can preserve the species. But it’s looking grim.

The species was formally recognized in 2017, when the American Ornithological Society split it from the Red Crossbill. It’s in grave peril of owning the distinction of being  the shortest-lived species known to science.