On the Fly — Birds of a Feather

Just because something is common doesn’t mean it’s not interesting. I relearn this whenever I stop and pay attention to everyday plants and animals. Right here, among the pickleweed and tules, are tales of invasion, sexual competition, infanticide and heroic adaptation like you won’t find anywhere else, except maybe an opera house.

“What a world of jubilation there is in their voluble whistlings and chirpings and gurglings, a wild medley of conquest which will strike terror to the faltering heart of the northern winter.” That was William Leon Dawson in 1921, describing red-winged blackbirds (Agelaius phoeniceus) mustering in springtime Santa Barbara for a trip north. And 90 years later, as you stroll past the cattails at Martinez Shoreline Park or McNabney Marsh or any of our other local wetlands, you’ll hear that same jubilation.

Ohlone weavers decorated their fanciest baskets with brilliant feathers from the wings of these blackbirds and from the heads of acorn woodpeckers, as members of the Vancouver expedition found in the late 1700s. So we know these birds have a longstanding home in California. And yet if you go to the red-winged blackbird page on the “Birds of the World on Postage Stamps” website, you’ll find a graphic demonstration of how widespread these birds are: They’re featured on stamps from Cuba to Canada, living year-round throughout this range.

The tricolored blackbird (Agelaius tricolor), on the other hand, is mostly endemic to California; about 95 percent of the world population lives here. What with dams, levees and development, we’ve reduced their freshwater marsh habitat severely, and they are now officially a California species of special concern. Maybe wetlands restoration efforts will help. And though they may not be as adaptable as some of the other blackbirds, they have in recent years begun to show up in Oregon and Washington.

You can distinguish a male tricolored blackbird from a male redwing by the border along its red epaulet. The redwing has a yellow stripe below its red shoulder patch, and the tricolor has a white band. The male Brewer’s blackbird (Euphagus cyanocephalus) is black all over with a green or blue tinge and bright yellow eyes. The females of these species are drab versions of the males, difficult to tell apart.

Red-winged blackbirds, tricolored blackbirds, Brewer’s blackbirds, great-tailed grackles, brown-headed cowbirds and European starlings form those flocks that sometimes darken the delta skies—millions of birds! But though starlings (Sturnus vulgaris) sometimes flock with these other birds, they are not really “birds of a feather”—they’re from a different family and a different continent. In 1890, the American Acclimatization Society, whose goal was to bring all the birds mentioned in Shakespeare’s works to North America, brought about sixty starlings from Europe to New York. Now there are hundreds of millions of them. These very adaptable birds have triumphed over other species for nesting spaces and are considered nothing but pests—clever mimics, but pests nonetheless.

Starlings’ beaks are longer and their tails shorter than those of the blackbirds, and in winter they have white spots on their plumage. A great-tailed grackle (Quiscalus mexicanus) can be distinguished from the other birds by (surprise!) its tail, which really is great. The photo here was taken in Texas, but grackles began to move into California in the 1960s and, according to Steven Glover’s Breeding Bird Atlas of Contra Costa County, they were first recorded in Martinez in 1985 and have been routinely nesting at McNabney Marsh, as well as other parts of the county.

And now we come to the brown-headed cowbird (Molothrus ater), smaller than other blackbirds, with a shorter tail, a thicker head and a short, thick-based bill that looks more like a finch’s than a blackbird’s. It has a brown head, but that’s hard to see except when the light is just right. The cowbird arrived in California around 1922 and it is a notorious brood parasite: like the Old Word cuckoo and some ducks, it leaves its eggs in the nests of other birds for them to raise. Cowbird young often hatch earlier than the host birds’ own babies, and they’re likely to be bigger and more aggressive. Whereas most of the host birds lay four or five eggs, a cowbird may lay 40 in a season.

It gets worse.

If an adult cowbird catches a host bird rejecting her eggs, she will destroy the host’s nest and injure or kill its nestlings. Ornithologists pondering the question of why host birds put up with brood parasites believe this is the answer and refer to it as the “mafia hypothesis.”

I’ll bring this dramatic column full circle by ending it with another quote from Dawson, who called the cowbird a “slattern, a shirk, a harpy, a traitor, an anarchist,” and an “avian marplot that lives only by stealth and by the secret practice of violence.”