Nature Notes: Spring’s Sweet Song: Cassin’s Sparrows in West Texas

The land lies parched. The prairie grasses are brittle. After months of dry winter weather, wind is blowing away the dusty soil of West Texas.

Then, on a warm March day – a song, piercing and sweet. Long before the cactus blooms, the Cassin’s sparrow announces the coming spring in West Texas.

First described in 1852, from a specimen in San Antonio, the Cassin’s sparrow is a creature of the prairies and desert grasslands. Its range extends from western Nebraska to central Mexico. It’s a year-round resident in West Texas, from Midland County to the foothills of the Davis and Chisos mountains. Populations here swell during the mating season in spring and summer.

The Cassin’s is a ground-dwelling bird – shy, and rarely seen. And, truth be told, it’s not much to look at. Brownish-gray, it stands 5 to 6 inches high. But its song, and its distinctive behavior, set it apart.

Michael Nickell is museum scientist at the Sibley Nature Center.

“It’s typically a very, very secretive sparrow,” Nickell said. “It’s very drab in color. In blends in to its environments. It hugs the ground a lot. It nests on the ground. So you usually don’t see it until the male is actually doing his performance. What stands out about them is the skylarking behavior of the males.”

What’s skylarking? Male Cassin’s sparrows engage in a unique aerial display.

Ascending up to 50 feet, the male sings as it flies – a series of clear, far-carrying notes. It’s an act of courtship, designed to woo potential mates. The birds also use the display to defend territory from other males. Skylarking is rare among bird species – and it’s especially rare among sparrows.

The Cassin’s first songs are soft. By late March, the skylarking is a lot bolder. As the season wears on, males launch from the highest perch in the area – from a fence post, or the top branches of a mesquite. The birds sing loudly, and, in late spring and summer, may perform through the night.

Apart from the song-flights, the sparrows remain concealed in grassy cover. They hop, walk or run. And they make their nests from prairie grasses, often with an inner lining of animal hair. The base of a tasajillo, or Christmas cholla, is a preferred nesting location.

But shrubs and brush are also critical for Cassin’s habitat. The males need a perch from which to skylark.

Henry Henshaw conducted pioneering bird studies in the 1870s. And he wrote lyrically of hearing the Cassin’s song in southern Arizona.

“It possesses an indescribable sweetness and pathos, especially when heard, as is often the case, during the still hours of the night,” Henshaw wrote. “During a night’s march from Camp Grant to Camp Bowie, I do not think an interval of five minutes passed unbroken by the song of one of these sparrows. Ere fairly out of hearing of the notes of one performer, the same plaintive strain was taken up by another invisible musician a little farther on, and so it continued till just before dawn.”

The Cassin’s coloration and secretive ways have made it hard to study. A Midland resident contributed more than anyone to our understanding of the bird.

Frances Williams was Midland County librarian from 1968 to 1979. She was an avid naturalist and taught natural history. Williams co-wrote a paper on the Cassin’s sparrow for The Life Histories of North American Birds. The paper remains definitive.

Williams described the sparrow’s diet. In fall and winter months, the birds rely on seeds. In the summer nesting season, they eat insects. In Midland County, miller-moths and their caterpillars are a major summer food source. Both parents feed their young nestlings.

Wiliams concluded that the sparrows could thrive without drinking water. She and her partner said that, in 20 years of observation, they’d seen a Cassin’s sparrow drink water only four times.

The Cassin’s avoids populated areas. But, on the West Texas plains, keep your eyes and ears open in the coming months. You might catch a sweet song of spring.

Nature Notes is underwritten by the Dixon Water Foundation and is produced by Marfa Public Radio in cooperation with the Sibley Nature Center. This episode was written by Andrew Stuart.


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