Cedar waxwings and toyon berries: It’s one of those iconic California food-web pairings, like black bears and manzanita berries or southern sea otters and sea urchins. In fall and winter, flocks of the black-masked birds swoop in on toyon shrubs laden with clusters of bright red berries, making their tea-kettle-like whistles.
Waxwings are known to feed cooperatively. A group may pass a berry from bird to bird until one eventually eats it, and members of a flock may politely take turns feeding at a shrub until they’ve picked it clean.
One of the few true frugivores (fruit feeders) among birds, the cedar waxwing can assimilate nutrients solely from fruit—low in calories and protein compared with insects—for weeks at a time. Toyon berries are technically pomes, like apples, and their seeds contain similar toxins. Green toyon berries are loaded with poisonous cyanogenic glucosides, but as they mature, their toxins shift from pulp to seed and the berries turn red, signaling their edibility. Waxwings safely pass the toxic seeds through their guts and back into the environment intact, in the process dispersing toyons to new areas.
As generalists, waxwings eat many types of berries (and insects in spring and summer), including some red cool-season berries that closely resemble toyon: Pyracantha and Cotoneaster. To tell the native toyon from these common nonnative shrubs, look for toyon’s thornless branches and serrated leaves.