Few relationships may be more quintessentially San Diego County than between the acorn woodpecker (Melanerpes formicivorus) and our native oaks. The rare Engelmann oak (Quercus engelmannii), with its leathery, blue-green leaves and stout branches, serves as the woodland backdrop for the vibrant visual and audio antics of the acorn woodpecker.

The Engelmann oak thrives in mesas, savannas, and woodlands above the coastal plain, but below 4200 feet (1,300 m), where colder winters occur. Once widely spread throughout Southern California and beyond, it now can be found only in a narrow band in our county due to suburban sprawl.

Acorn woodpeckers are a lively troupe of feathered friends, who readily utilize the remaining populations of Engelmann oaks. With their parrot-like squawks, they are commonly heard before seen between the branches and open spaces of the oaks, even with their distinctive black-and-white coloration. Each year, they store thousands of acorns into “granary trees” by jamming them into perfectly sized pecked-out holes. 

The Engelmann oak, with its evergreen leaves, provides shelter for the woodpeckers’ extended family groups. Multiple males and females join forces to raise individual nests, all the while defending permanent territories within the woodland. The oak’s blue foliage, which aids in tolerating our intense summer sun, illustrates its adaptability to drought and high temperatures, much better than other oaks, something our woodpeckers and hundreds of other diverse species appreciate.

If you have the room for a majestic Engelmann oak to grown in your outdoor space, you’ll be able to watch as this rare native oak and the lively acorn woodpecker form a partnership that not only adds vibrancy to your garden but also contributes to the rich ecological fabric of San Diego County and beyond.

Additional Animals

Pacific Tent Caterpillar (Malacosoma constricta)
When it’s time for a nap, Pacific tent caterpillars build silken tents at branch, stem, or trunk nodes of Engelmann oaks and other broadleaf trees.

Yellow Wig Gall Wasp (Druon fullawayi)
Many woodland oak species form these fluff balls in reaction to the egg laying of a 1.5-2.25 mm wasp. Like other galls, this structure houses chambers of wasp larvae, providing shelter and food until they emerge as an adult.  

Townsend’s Big-eared Bat (Corynorhinus townsendii)
Townsend’s big-eared bats forage for moths and other insects in oak woodlands, and will roost in the branches as well. 

Additional Plants