San Diego Natural History Museum--Your Nature Connection[San Diego County Bird Atlas Project]

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Red-winged and Tricolored Blackbirds

The Red-winged and Tricolored Blackbirds are confusingly similar in plumage and strikingly different in their nesting habits. Few more fascinating examples of different biology concealed by similar morphology can be found among birds. The Red-winged is one of the most widespread species of North America, while the Tricolored is narrowly restricted to the Californian biogeographic region. Thus we in San Diego are in a great position to appreciate this remarkable pair of species.

[Female Red-winged Blackbird (neutralis), Fresh plumage.] [Female Red-winged Blackbird (neutralis), Worn plumage.] [Female Tricolored Blackbird, Fresh plumage.]
Female Red-winged Blackbird (neutralis),
Fresh plumage.
Female Red-winged Blackbird (neutralis),
Worn plumage.
Female Tricolored Blackbird,
Fresh plumage.

The adult male Red-winged Blackbird, with his red epaulet on a black body, is one of the most familiar of American birds. Yet this simple fa?ade conceals variation of a complexity rarely equaled. When I give tours of the museum's bird collection and need an example of how many specimens may be needed to show what one species looks like, I always select the Red-winged Blackbird. The streaked females, of course, differ grossly from males, and the juveniles differ appreciably even from the females. Males take two years to achieve their definitive plumage, and the first-year males vary greatly among themselves in the heaviness of their streaking. Even though the Red-winged Blackbird molts only once per year, the fresh plumage of fall and early winter differs greatly from the worn plumage of late spring and summer, in both males and females, because the new feathers have pale or buff edges on them that, over the course of the year, wear off completely. Finally there is great geographical variation in the species in plumage color, plumage pattern, and bill shape. This variation is concentrated in California, the home of no fewer than seven subspecies of the Red-winged Blackbird.

The Tricolored Blackbird dispenses with some of the Redwing's complications. Though the Tricolor's sexual dimorphism is parallel, the immature males acquire a plumage very like the adults' in their first fall. The effect of plumage wear is less obvious because the feather edges are narrower and less contrasting to begin with, and there are no subspecies. Fortunately, only one subspecies of the Red-winged, neutralis, occurs in San Diego County commonly.

The complex differences between the two species in plumage may be presented best in a table. Easiest of all to distinguish are the females in fresh plumage. In fall the female Redwing, with her buff and chestnut feather edges, is a thing of beauty. At this season the female Tricolored is far more subdued. Over the year, however, the edges gradually wear off the feathers, and the differences between the two species recede as summer approaches. By midsummer, the streaking on the upperparts of the female Redwing may be practically obliterated. Even on the underparts the whitish streaks become narrower and less conspicuous. The female Tricolor, meanwhile, becomes almost totally black, with streaking remaining only on the throat. In San Diego we can be thankful we don't have to contend with the subspecies of the Redwing in the San Francisco Bay region, mailliardorum, whose females resemble those of the Tricolor far more closely and when worn may not be distinguishable from it from gross appearance alone.

Key to Redwing/Tricolored Blackbird Identification
Red-winged Blackbird (subspecies neutralis)
Tricolored Blackbird

Wing less pointed with shorter primary projection
Bill thicker and blunter

Wing more pointed with longer primary projection
Bill longer and more sharply pointed

Fresh plumage (fall) - males
Epaulet orange red with buff fringe
Upperpart feathers boldly edged chestnut

Epaulet blood red with white fringe
Upperpart feathers with only obscure grayish brown edges

Fresh plumage (fall) - females
Head and back heavily streaked with buff and chestnut
Underpart feathers with buff or whitish edges so broad that the entire belly is heavily streaked and the undertail coverts are boldly scalloped
Wing feathers with crisp broad buff and chestnut edges recalling a juvenile shorebird's

Head and back feathers with narrow gray-brown edges that blend softly with the black centers
Breast and belly feathers with gray edges narrow and blended, distracting little from the impression of largely black underparts
Wing feathers with dull gray-brown edges, much narrower than on the Redwing

Note: Any chestnut in the plumage instantly distinguishes the Redwing from the Tricolored.

Worn plumage (summer) - males
Familiar "onk-a-lee" song has a pleasant musical, if mechanical or electronic, quality
Buff fringe on epaulet variably faded

"Song" of Tricolored is nasal, notes indistinct, more like the bleating of a young goat or sheep
White fringe on epaulet variably stained

Worn plumage (summer) - females
Whitish streaks of underparts become narrower but normally retain streaking
Streaking on the back may be practically obliterated.

Underparts become almost totally black, with streaking remaining only on the throat
Upperparts uniformly black

One-year-old males
Males take two years to achieve their definitive plumage. First-year males vary greatly in the heaviness of their streaking.

Immature males acquire a plumage very like the adults' in their first fall.

Juveniles (fledging to August only)
Entire underparts streaked, more narrowly and softly than on adult female.
Flight feathers on wings broadly edged buff and chestnut

Entire underparts streaked, including belly, more broadly than in juvenile Redwing
Flight feathers on wings narrowly edged dull brown

Fortunately, at the time of year when they are most similar, the Redwings and Tricolors are nesting, and their profound differences in nesting biology readily identify them. The Redwing follows a strategy more or less traditional for a songbird, with each male advertising a territory and defending it from other males. Each male, though, may have a harem of several females nesting within his territory—up to 15 have been recorded. This leaves a surplus of nonbreeding, nonterritorial males that hang out in bachelor flocks, often at feedlots. Where the birds are nesting in marshes, the territories may be quite small—as little as 153 square meters, though 1600 is average, and territories are larger in other habitats.

The Tricolored Blackbird, on the other hand, follows the model of colonial seabirds. Males maintain no individual territories, and females may nest barely out of pecking distance of each other. The colonies may be enormous—formerly of up to 200,000 nests—and a colony of 20,000 nests has been found packed into a marsh of only 10 acres. The birds within a colony are closely synchronized, so that all young hatch and fledge within a few days of each other. But different colonies may be quite unsynchronized, some establishing themselves two or three months after others. Some colonies, like that at Jacumba, are used year after year, but others, like those around Ramona, shift abruptly from one year to the next. When hundreds of birds are singing from a colony at once, the effect is surreal and identifies the birds as Tricolored Blackbirds long before the observer can focus on a single bird. The Tricolored Blackbird is unique among North American songbirds and one of California's remarkable natural treasures.

Unfortunately, the Tricolor's intensely social yet nomadic habits and preference for nesting in freshwater marshes put it at risk. Numbers throughout the species' range have declined seriously, and this decline has been proportionately greater in coastal southern California than elsewhere. Large colonies may be necessary for adequate predator defense and proper social stimulation—the Tricolored Blackbird has been called California's Passenger Pigeon. When I was a child in the 1960s, I regularly saw flocks of thousands of blackbirds, mostly Tricolored, commuting north-south over my parents' house in East San Diego. Until about 1980, the flamingo pond at the zoo was one of the easiest places to see Tricolored Blackbirds. Now our atlas results show them relegated largely to scattered colonies inland. The county population now is probably no more than 10,000 birds, which could be seen in a single day 40 years ago. We now have a good idea, thanks to the atlas, where the remaining colonies are located. But because of the species' nomadism, not all colonies are active every year, and to sum the colonies over the entire atlas period would overstate its abundance.

The Red-winged Blackbird is clearly a much more adaptable and therefore widespread species. Most squares on the coastal slope have small ponds or riparian strips enough for at least a few. Still, it is not really an urban adapter, as revealed by the several squares in metropolitan San Diego where the species is lacking. The distribution spills down toward the desert along San Felipe Creek as far as the mouth of Sentenac Canyon in square J23 and Carrizo Gorge in R27. It's still an open question whether the birds nesting in the Borrego and Vallecito valleys are the coastal subspecies neutralis or the thin-billed, pale-femaled subspecies sonoriensis common in the Imperial Valley. Scattered records from more remote places in the Anza-Borrego Desert—as well as a couple of old fall specimens of sonoriensis from Jamacha—suggest that the isolation of these subspecies isn't total.

Known Tricolored Blackbird Colonies in San Diego County, 1997-2000
Colony Square Years known Active Maximum count Observers
Dameron Valley C15 1997, 1998 200 K. Weaver
Oak Grove C16 1998, 1999 840 K. Weaver
Sunshine Summit D17 1999, 2000 25 P. Unitt
Puerta La Cruz E18/F18 2000 50 P. Unitt, M. Mathos
Swan Lake F18 2000 1,000 P. Unitt, M. Mathos
Warner Ranch G18 1999, 2000 18 P. Nelson, J. K. Wilson
Mesa Grande NW H16 1999 12 E. C. Hall, J. O. Zimmer
Pamo Valley I15 2000 1,280 W. E. Haas
Mesa Grande SE I17 2000 160 W. E. Haas
Santa Ysabel Ranch I18 2000 260 S. Smith
Boden Canyon J14 1999 40 C. Mahrdt, R. L. Barber, O. Carter
Ramona W.D. Pond K13 1998, 2000 1,000 P. von Hendy, W. E. Haas, P. Unitt
East Ramona Pond K15 1998, 1999 400 M. & B. McIntosh
Lindo Lake P14/O14 1997, 1998, 2000 220 M. B. Stowe
Viejas Casino P18 1999, 2000 600 K. Winter
Tule Lake T27 2000 30 J. K. Wilson, F. L. Unmack
Twin Lakes U20 1999, 2000 100 R. & S. Breisch
Campo U23 1997, 1998, 1999, 2000 1,000 D. & A. Hester
Jacumba U28 1997, 1998, 1999, 2000 300 F. L. Unmack
La Media Rd. V13 1998, 1999, 2000 80 P. Unitt

Red-winged Blackbird distribution grid.
Red-winged Blackbird

Black - Breeding confirmed
Medium Gray - Breeding probable
Light Gray - Breeding possible


Though both the Red-winged and Tricolored Blackbirds are linked to wetlands, this linkage is not simple. For example, on Otay Mesa, at Siempre Viva and La Media roads (square V13), where I found both species nesting in 1999, both came to forage for insect larvae along the shore of the pond. But the nesting areas were over dry ground, the Redwings in rank vegetation just west of the road, the Tricolors in a stand of dry weeds about a quarter mile away. Near Mesa Grande Road and Highway 79 (I18), Sue Smith found the Tricolors nesting in blackberry thickets, a habitat noted for the species in northern California. Nevertheless, most colonies of the Tricolor are in cattails in ponds, the water below being a deterrent to predators.

For foraging, these blackbirds throw any pretense at specialization out the window. Both species feed on the ground, in the open. Mudflats, lawns, plowed fields, dairies (cow pies, more specifically), garbage dumps, and supermarket parking lots all may serve as foraging habitat. Like most members of the family Icteridae, these blackbirds instinctively forage by inserting their bills into some soft substrate, then prying them open to capture invertebrates. During our June 2000 Lake Henshaw blockbuster weekends we saw a thousand Tricolored Blackbirds feasting on millions of grasshoppers—the staple food of large colonies. But the birds' flexibility extends to scavenging a variety of the waste left by human civilization. The Tricolored Blackbird surprises us yet again--a declining songbird of the most specialized nesting habits, highly sensitive to disturbance of its colonies, possibly facing extinction in the 21st century—feeding eagerly on garbage.

Thanks to Bill Haas for his review of this article and many ideas on the biology of the Tricolored Blackbird.

--Philip Unitt

Tricolored Blackbird distribution grid.
Tricolored Blackbird

Sketches by Nicole Perretta

Focus On ... | Fall 2000 Wrenderings | Bird Atlas Introduction