(Originally published in the Sept – Oct 1998 issue of the Albatross, Vol. 44, no. 1) 

Poison Oak: A Birder’s Friend or Foe? 

By Jeff Davis

It waits with idle pugnacity for unsuspecting victims; one careless move and a hominid may suffer its wrath, maybe not today, maybe not tomorrow, but eventually. Calamine lotions, tecnu showers, cortisone injections, and, in extreme cases, even hospitalization may be necessary to overcome the itchy and blistery skin ailment. Our typical approach to this native but noxious plant and its relatives is evident in the title of a 1972 USDA Bulletin "Poison-ivy, Poison-oak, and Poison-sumac: Identification, Precautions, Eradications." Although this cunning member of the cashew family may seem outstandingly evil to us, many birds enjoy a different relationship with this toxic weed.

 Aside from use of the shrub as cover and potential substrate for nests, its small white berries help many species survive the cold, food-short, months of winter. In the April Fools issue of this newsletter, I was poked fun at for reporting that I had watched a Ruby-crowned Kinglet eating poison oak berries. Although it may not have the same appeal of a rare bird sighting, at the time I had thought it was similarly rare to see this noted insectivore turning to a vegetarian fare. However, according to the Dover 1961 reprint of" American Wildlife & Plants: A Guide to Wildlife Food Habits," these small berries make up 5-10% of the kinglet's diet during fall and winter in California. In fact, the authors of this book list about 25 bird species that eat these fruits. In addition to many that they list, I've seen six other species dine on these delightful victuals.

 The species I see eating the berries most often is the Wrentit. Fittingly, the Dover book lists poison oak fruits as making up 10-25% of the Wrentit's diet. Others that eat these important fruits include quail, woodpeckers, vireos, jays, chickadees, wrens, thrushes, thrashers and sparrows. I once watched a Yellow-rumped Warbler consume eight berries in about three minutes, which seems like a lot of berries for a bird that weighs less than a fifty-cent piece. The birds receive protein, fat and carbohydrates in exchange for dispersing the seeds of poison oak. The tiny seeds within the berries require some sort of scarification in order to germinate; and passing through the digestive tract of a bird seems to be the right prescription.