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Mike Jacobs

ALWAYS IN SEASON: Yellow-headed blackbird has reason for his poses

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The yellow-headed blackbird is a kind of poseur, taking on different roles as circumstances warrant. He can be submissive or aggressive. He can be elegant and patrician. Or he can be raucous and rowdy.

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But of course these roles are natural to him; he isn’t pretending to be something he is not. Instead, he is competing for reproductive advantage, so these roles are vital in his daily life, which is spent largely in overgrown marshes on the Great Plains.

The masculine pronoun is used here, because it is the male of the species that is conspicuous by his appearance, voice and behavior. The female is plainer, much less obvious and quieter into the bargain.

In fact, these blackbirds display an unusual degree of sexual dimorphism — a subject we’ve encountered here before. The term refers to the difference between males and females of a single species.

Yellow-headed blackbirds are dimorphic in appearance and in size. The male is much larger — by almost a third in length and mass — than the female.

It is the male that has the yellow head, and this makes him immediately recognizable. In flight, he shows prominent white patches in the wings. In a bird at rest, these are reduced to stripes along the back.

The yellow-headed blackbird’s relatively large size — the largest of the blackbirds in North America — helps make him obvious, as well. And it abets his apparent changes in mood.

The body is relatively stocky, but the bird can extend its neck, bringing more prominence to the brilliant yellow plumage and thus taking on an aggressive appearance.

Pulling back the neck reduces the amount of yellow and makes the bird look very much more docile.

At rest, the yellow-headed blackbird has a noble look, with a smooth contour across the neck, head and chest, again displaying the brilliant yellow fathers.

These are accented by a bit of black behind the bill and below the eye, giving the face a distinctive pattern.

Yellow-headed is an appropriate name for the species, but sometimes, the yellow runs almost to brilliant orange. This is especially true among courting birds early in the breeding season.

Females are plainer, resembling females of other blackbird species in both size and shape. They do show quite a bit of yellow, however, and so they can be separated from the much darker and more heavily streaked females of other blackbird species.

Males are noisy birds; David Allen Sibley in “The Sibley Guide to Birds” describes their noise this way: “Song extremely harsh, unmusical; a few hard, clacking notes on different pitches followed by wavering raucous wail like a chainsaw.”

This is accurate enough, even though it seems a little pejorative. (Personally, I kind of like the noise; it evokes the prairie landscape for me.)

Of course, there is a reason for all of this. It has to do with the mating system of the yellow-headed blackbird.

These birds are polygynous. One male mates with several females. This means that competition is keen, and victory goes to the larger, more brightly colored, more aggressive and perhaps the more raucous birds.

Yellow-headed blackbirds are abundant — but they have quite specific habitat requirements. They are birds of prairie wetlands and they always nest over water.

In his “Breeding Birds of North Dakota,” Robert Stewart reported that 58 percent of the nests he found were in bulrushes, mostly hardstem bulrushes, and 39 percent were in cattails.

The average depth of water below the nests was 18 inches, ranging from 3 inches to 32 inches.

Nests averaged 18 inches above the water surface.

Cattails and bulrushes are common plants of prairie wetlands. Bulrush is sometimes called “tule,” as in “out in the tules,” or very far away.

Yellow-headed blackbirds occur across North Dakota and in Minnesota, except for the northeastern region.

They can be encountered in marshes with standing water; perhaps the best places locally are Kellys Slough National Wildlife refuge northwest of Grand Forks and Agassiz National Wildlife Refuge in northwest Minnesota.

The birds are also abundant in ditches along U.S. Highway 2 in the Devils Lake area.

Jacobs is a retired publisher of the Herald. Reach him at mjacobs@polarcomm.com.

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