PART III: The symbiosis between roof rats and a western mockingbird


October 26, 2020

Editor’s Note: This is Part III of a three-part series.

A female western mockingbird (Mimus polyglottos leucopterus) developed an interesting, beneficial relationship with roof rats at this location. The rats did the heavy lifting at night by gnawing through the tough, leathery citrus fruit rinds and exposing the sweet endocarp to the bird. When the rats were ensconced in their protected harborages during the day, this mockingbird had unhindered access to damaged fruits during daylight hours.

In fact, she became habituated and conditioned to obtaining free meals by capitalizing on the rats’ destructive work. Casual diurnal observations could deceive a person into believing that it was the mockingbird that was responsible for the damage to citrus fruits at this location, not rats. In the spring, I watched as the bird, its beak full of citrus fruit vesicles, fed her fledgling. Later in the season, she also caused heavy damage to apricots, plums and tomatoes in my backyard.

Western mockingbirds resemble the more common northern mockingbirds (M. polyglottos), but are generally only found “in the western portion of North America ranging from northwestern Nebraska and western Texas to the Pacific Coast, and south to Mexico (the Isthmus of Tehuantepec), and Socorro Island. It is larger than than the northern species and has a slightly shorter tail. Upper parts are more buff and paler, and the underparts have a stronger buff pigment.” (Source: Brewer, D. [2001]. Wrens, Dippers and Thrashers.)

Dr. Hanif Gulmahamad, BCE, is an urban and structural entomologist and consultant based in southern California.



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