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 February 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...