LeConte's Sparrow

Reserve Program (CRP). Since 1990, we have been surveying breeding birds in over 400 fields in nine counties in North Dakota, South Dakota, Minnesota, and Montana. Many of these fields have been visited every year. A long-term and broad-scale study of this magnitude would not be possible without the support and cooperation of private landowners; for this, we are extremely appreciative.

CRP has been a boon for nesting waterfowl during the last decade. The values of the CRP to other birds, such as the Le Conte's Sparrow, are less well known, but data from this and other studies indicate that many other birds have benefited from CRP as well. The Le Conte's Sparrow is just one of over 100 species of birds that we have observed between 1990 and 1998 using these CRP fields during the breeding season. Some species of birds are fairly common in CRP fields, including the Grasshopper Sparrow, Savannah Sparrow, Clay-colored Sparrow, and Bobolink. Others are found only in low numbers in CRP fields in this region, such as the Henslow's Sparrow, the Nelson's Sharp-tailed Sparrow, and Brewer's Sparrow. And some, such as the Le Conte's Sparrow, are abundant in some years and rare or absent in others.

The Le Conte's Sparrow is arguably among the most poorly known of North America's grassland birds. The species is one of several sparrows belonging to the genus Ammodramus. Ammodramus sparrows occur primarily in grasslands and wetlands in North America, and are notorious for their cryptic plumage and secretive behaviors. The Le Conte's Sparrow is no exception. During the breeding season, the Le Conte's Sparrow is extremely secretive, skulking about and diving into vegetation with unbelievable agility. Both adults and juveniles often escape attention by running along the ground in dense cover rather than flying. This elusive behavior has been described as mouse-like by some and as frustrating by others, especially those interested in catching a glimpse of a bird. The species' cryptic plumage is more colorful than most grassland sparrows, and the species is considered by many to be one of the most attractive sparrows in North America.

Only the male Le Conte's Sparrow sings, often from a concealed location within dense vegetation. Their song is weak and short, resembling an insect more than a bird. The song is barely audible over the similar calls of the crickets, grasshoppers, and other sounds of the grasslands. Ernest Thompson Seton, a renowned naturalist and artist, described the Le Conte's Sparrow song as "so thin a sound, and so creaky, that I believe it is usually attributed to a grasshopper." Thomas Roberts, a well-known Minnesota ornithologist, described the species' song as an "amusingly squeaky little ditty." Although Le Conte's Sparrows sing throughout the day, they tend to sing more often in the evening and at night.

During the breeding season, the Le Conte's Sparrow generally prefers moist grassland and wet meadow habitats. The species tends to avoid areas with woody vegetation or permanent standing water, although they often are found along the peripheries of wetlands. This affinity for moist habitats has resulted in the species being known more as a wetland bird or wet meadow species than as a grassland bird. This confusion probably reflects the similarity in grassland-like vegetation that is characteristic of both wetlands and grasslands within the species' breeding range.

Habitat preferences also likely explain the species' use of CRP grasslands in our study. The perennial grassland habitats established by the Conservation Reserve Program are similar to other upland habitats -- such as prairie and hayland -- used by the Le Conte's Sparrow elsewhere in its breeding range. Although vegetation varies considerably among CRP fields, most CRP land in the northern Great Plains was planted to a mixture of legumes and grasses.

 

Le Conte's Sparrows were nearly absent from CRP fields that we surveyed between 1990 and 1993. In 1994, however, Le Conte's Sparrow populations experienced a dramatic increase in the region. This increase continued in subsequent years, and by 1996 the Le Conte's Sparrow was one of the most common breeding birds in the CRP fields that we surveyed. The species was most common in 1994 to 1997 in Eddy and Kidder counties in North Dakota, which lie within the species' usual breeding range. The species also increased in counties on the southern edge of its breeding range (Day County in South Dakota, Grant County in Minnesota, and Sheridan County in Montana), as well as in counties that are outside of the species' normal breeding range (Hettinger County in North Dakota and McPherson and Butte counties in South Dakota). By 1997, Fallon County, Montana was the only one of nine surveyed counties in which Le Conte's Sparrows were not found.

Why did Le Conte's Sparrow populations increase so dramatically? Given what we know about the Le Conte's Sparrow's preference for moist grassland habitats, we suspect that climatic variability in the region may have been a major factor leading to these dramatic fluctuations in Le Conte's Sparrow abundance and distribution. The climate of the northern Great Plains is highly dynamic, with great annual variation in precipitation and periodic, often extreme, wet and dry cycles. In particular, drought is a major force of disturbance on the Great Plains, and has been an important influence in directing the evolution of grassland plants and animals in this region.