March 18, 2023

Are Chickadees Hybridizing and Is That a Bad Thing?

Mountain chickadeee (Poecile gambeli). Cornell University

A recent Audobon Society article spoke to possible hybridization between mountain chickadees and black-capped chickadees (more common at lower elevations) here in Colorado:

Black-capped and Mountain Chickadees mate more often than previously believed, research shows—especially where people disturb their habitat. 

Three chickadees clung to a suet feeder outside Denver, but one of them looked different from the others. Unlike the two Black-capped Chickadees, an eBird user noted in December, this one had a faint white band above its eyes, characteristic of a Mountain Chickadee. In July, at the Randall Davey Audubon Center in Santa Fe, another birder spotted a chickadee with a Mountain’s white eyebrows and a Black-capped’s buff sides and white-edged wings. Similar birds have popped up in Salt Lake City, Albuquerque, and other Rocky Mountain metros. 

Prior to eBird’s creation in 2002, the scientific literature held only three records of hybridization between Black-capped and Mountain Chickadees, each report more than 25 years old. But in the past few years, Kathryn Grabenstein and Scott Taylor, evolutionary biologists at the University of Colorado Boulder, noticed that eBird users commonly spot hybrids of the two species in the West. The platform includes more than 800 such reports today, many of them from cities and towns. The researchers decided to look further into the phenomenon.

Funny thing, here in the foothills of the Wet Mountains, essentially a young (post-1960s) ponderosa pine forest mixed with a Gambel oak understory, I see both chickadee species about equally in smal numbers, usually no more than two of each at a time. This habitat has evolved and contains houses, but I would not say that there is a large number of introduced deciduous trees.

"Species "is a human concept, and definitions are often changed. There used to be several species of juncos, for example, and then the American Ornithological Society decided that there was only one: the dark-eyed junco. Bye-bye, Oregon junco and the rest.

Nature writer Emma Marris comments in her new book Wild Souls: Freedom and Flourishing in the Non-Human World (the paperback subtitle is What We Owe Animals in a Changing World),

One approach to sorting out whether animal hybrids are "good" or "bad" in terms of biodiversity is to ask whether the resulting organisms will be more resiliant and likely to persist in the face of the ongoing processes of environmental change that we humans have kicked off. Another way is to investigate whether the individual hybrids themseves will be more or less able to be happy and flourish.

So as long as a there is a chickadee out there doing chickadee stuff and living in the trees, it's all right, she would say.

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