Orioles fly north with a flap: Bird population dwindles

March 22, 1992|By Bruce Reid | Bruce Reid,Staff Writer

Baltimore orioles -- the songbirds, not the ballplayers in orange and black -- are flying north to Maryland each April in ever-decreasing numbers.

Researchers say Maryland's state bird is suffering the same steady decline being experienced by many of its colorful cousins that also nest in North America and spend winters in the tropics.

Reasons for the bird's decline -- roughly 30 percent -- in recent years are not entirely clear, said M. Kathleen Klimkiewicz, a biologist at the U.S. Fish and Wildlife Service's Patuxent Wildlife Research Center in Laurel.

But she and other researchers believe a double whammy of tree-cutting in both its summer range in North America and its winter range in Central and South America is the main culprit.

Chopping up woodlands into smaller and smaller blocks -- a process biologists call forest fragmentation -- means birds can't find as many places to nest, so they can't reproduce as fast as they once did. Smaller woodland tracts also make nesting birds more susceptible to predators such as blue jays, cowbirds and cats -- as well as humans who disturb them.

Across North America between 1978 and 1987, the number of Baltimore orioles and their Western cousins, Bullock's orioles, declined each year by an average of about 3 percent, statisticians say.

While that would indicate a 30 percent total decline over the period, Bruce Peterjohn, coordinator of the Fish and Wildlife Service's nation wide breeding-bird survey, says that because of difficulties in counting birds precisely, the actual figure could be a bit more or less.

Maryland shows a comparable pattern, says Ms. Klimkiewicz, who is helping edit the Breeding Bird Atlas of Maryland and the District of Columbia. The atlas, to be published next year, is a joint project of the Maryland Ornithological Society and the state Department of Natural Resources.

But the oriole hardly faces extinction. The bird, about the size of a cardinal and no less stunning in color, still is fairly common across much of the state.

The bird, from which Baltimore's baseball team has taken its name and colors since the late 1800s, builds its hanging nest on farms, as well as in the moist forests along inland rivers such as the Gunpowder. It also can be spotted in sycamores and other large trees at Lake Roland and similar environs around the city, Shirley Geddes of the Baltimore Bird Club says.

Annual breeding-bird surveys in Maryland and other states are conducted each June. Bird counters drive prescribed routes, stopping every half-mile, to look and listen for any winged species they can find.

Lately, Ms. Klimkiewicz says, the "oriole is a bird you hope to get, but you don't always get them. Or you don't get more than one." She drives four 25-mile-long breeding-bird routes.

Orioles "are not nearly in the trouble some other species are," Ms. Klimkiewicz says.

Various warblers, thrushes, flycatchers and other "neo-tropical" migratory species are declining at faster rates, she says.

One bit of good news: Since the 1950s, the oriole has expanded its breeding range in Maryland to the western shore of the Chesapeake Bay. Ms. Klimkiewicz and her colleagues don't know why.

Lovers of shade trees, or trees in general, should cheer for the bird.

Orioles eat damaging insects, "often destroying whole infestations of the forest tent caterpillar," the bird-breeding atlas will report. They also eat larvae of the gypsy moth, that scourge of Eastern woodlands, as well as beetle larvae, plant lice, ants and other insects.

Some people will remember that the Baltimore oriole was relegated to the level of subspecies about a decade ago. The American Ornithologists' Union, the Supreme Court of bird-naming, ruled that its official name should be the northern oriole. That's because it was found to be interbreeding with western Bullock's oriole where the two birds' ranges overlapped.

But because the males of the Eastern and Western forms are dressed a bit differently, "It is still common to use the names Baltimore and Bullock's" orioles, the atlas says.

The Baltimore oriole was officially named by Carolus Linnaeus, the famous Swedish naturalist, in 1766. Legend has it that earlier, George Calvert, the first baron of Baltimore, fancied the oriole's plumage and took its colors for his coat of arms.

A different version of history has Cecilius Calvert, second baron of Baltimore, with more of a hand in the bird's early notoriety.

Over time, the Baltimore oriole has acquired a number of nicknames, including golden robin, fire-hang-bird and hammock bird. The latter two hint at the bird's engineering skills. Bird fanciers have long regarded the oriole's nest as a fine example of overkill.

As far back as 1917, ornithologist George Gladden wrote in his classic text, "Birds of America": "Why should a creature, who is in no more danger of falling than a fish is of drowning, plaster a mass of mud, twigs and grass on a limb as thick as one's thigh, or in a crotch which would support a 5-ton steel safe?"

Further, Mr. Gladden wrote that "it is my Lady Baltimore, not his lordship, who is the designer and maker of this picturesque and appropriate habitation. Indeed, it appears that while my lady toils, my lord does nothing much but sit around and whistle and look gorgeous."

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