Monday, July 26, 2010

Among the Grasses: Western Meadowlark

Western Meadowlark. Image by Doug Brown

The melodious notes that rang out over the shrubs and grasses of the lower Jemez Valley signaled the territory of a certain grassland obligate species, the Western Meadowlark, one of our most popular birds. Six states list the Western Meadowlark as their state bird. Their song is almost certainly familiar, among the most beautiful and complex of North American birds, although the meadowlark often remains unseen as he sings from his exposed perch on a low shrub. It is one of our most abundant and widely distributed grassland birds, inhabiting open country from natural and planted grasslands of the Northern Great Plains to tidal flats along the Pacific Ocean, and from sea level to mountain meadows.

When viewed from the back, his and her colors are cryptic, designed to blend in with their desert, grassland or shrubland backdrop. But, when viewed from the front, this gifted songster can be easily recognized by the bright yellow breast with the V-shaped black bib. Despite the fact that its appearance is distinctively yellow and brown, it is most closely related to the blackbird family that includes Red-winged Blackbird, grackles, and orioles. It also is closely related to the Eastern Meadowlark, remarkably similar in appearance but with a very different song, equally captivating despite its more simple tune.

It would seem logical that two species that diverged at some point in their evolution due to differing habitats, would evolve different feather coloration, but they are nearly impossible to tell apart. Over time, their respective songs have changed greatly. It is by listening that one most oven can tell them apart. Today, both meadowlarks can be found in New Mexico, sometimes in overlapping areas. So, they look alike but sing a different tune. Might one be attracted to the other? Studies have shown that the two species hybridize only very rarely, and then only at the edge of the range where few mates are available. Captive breeding experiments found that hybrid meadowlarks were fertile, but produced few eggs that hatched. Obviously, their sense of self, as well as nature, protects the species from becoming hopelessly intermingled.

The nest of the Western Meadowlark usually is partially covered by a grass roof, but nests vary from completely open to a complete roof and an entrance tunnel several feet long. When Western and Eastern Meadowlarks nest in the same area, the Western Meadowlark male will defend his territory against all male meadowlarks of either species. He usually has two mates at the same time and they do all the incubation and brooding, and most of the feeding of the young.
Although the overall population of Western Meadowlark continues to remain high, long-term studies have shown an ongoing decline (1966-2006). For meadowlarks that nest in cultivated fields, haying, or tilling to control weeds, destroys all young unable to fly and a high number of incubating females. Conversion of cultivated fields to planted grassland benefits the species, but may not be possible given the demands of our ever-expanding population. Delaying the use of heavy equipment until young have fledged would certainly improve nest success. This; however, is unlikely to be a factor in the largely uncultivated region of western New Mexico. Grazing appears to have little impact on populations of Western Meadowlark.

Like many species of birds, solid information about the decline in populations of the meadowlark is lacking and more research is needed. Like a juggler with too many objects afloat, there are simply not enough financial resources to study every animal to the fullest extent possible to determine the best management practices for that species. The threats that challenge meadowlark populations are common to, not only the many grassland birds in decline, but other wildlife of the Great Plains grasslands. Finding a solution will not be easy among the many interests that compete for precious land use. Most often, when humans and wildlife compete, it is the animals that suffer. Let’s hope that the crystal clear notes in the hauntingly melodious song of the meadowlark does not become only a distant memory, a story to be told to our great grandchildren.

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