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Cassin's Sparrow

550px-cassins_sparrow
photo courtesy of: birdforum.net

Season 5, episode 14

From the Northern reaches of the Llano Estacado in Eastern New Mexico to the Big Bend Borderlands of Texas, this is Nature Notes.

The Cassin’s sparrow is a fairly non-descript small gray bird. But in the spring, its song and antics to attract a mate are something to behold. What makes it so special?

From Marfa Public Radio, in cooperation with the Sibley Nature Center in Midland, Texas, this is Nature Notes. Hello, I’m Dallas Baxter.

The first Cassin’s Sparrow song of the year is a blessing to eagerly await. For most of the year Cassin’s sparrows are secretive. But in the spring, the male sings a melody that rises and falls, going up the scale as he flies up, going down the scale as he comes down. This behavior is known as “skylarking.” In Midland County, Texas, the Cassin’s sparrow’s skylarking song is a sign that spring is on the way.

With his song, the male Cassin's Sparrow enthralls the female. At first he has to chase her, to convince her to listen. Later she sits low on one of his singing stations -- he never begins the song flight from the ground. She sometimes joins him in flight, flying in close tandem high in the sky.

Small birds have many predators. The Cassin’s sparrow fears the periscope of the coachwhip snake. The Coachwhip lifts the front third of its body to peer over the grass as it moves, implacably watching and waiting for a tasty songbird.

Cassin’s sparrows are also prey for Roadrunners. Antediluvian, crest cocked, orange and blue warpaint gleaming on the skin above its eyes, tail lowered, body taut, the roadrunner canters along rabbit and human footpaths. The sun brings forth a green iridescence on its back. It will seize a sparrow in its vise-grip beak and with quick strikes of its short serpentine neck, repeatedly smack its prey to death on the hardpan soil, tenderizing the small bird into a shapeless feather-ball before gulping it whole.

The shy Cassin’s sparrow is always on the alert. A bramble of grass, usually Bush Muhly, is a favorite nesting site. A Cassin’s sparrow’s nest is a small cup of grass, lined with animal hair (or shredded grass if hair is in short supply). Both parents feed the young, specializing in the grassland miller-moths and their caterpillars - plentiful food that sometimes number in the millions.

The late spring food of the fledged young sparrows consists of insects like grasshoppers, caterpillars and beetles. They also eat the seeds of weeds and grasses.

After the young are raised, Cassin’s Sparrows are silent. They skulk, a quick flip from a nearby bush to further cover is the most they show of themselves. Only when predators amble by, do they pop up, to keep apprised of deadly sneaks. A month may pass without the sparrows’ presence being noted, but they remain, gleaning the prairie’s harvest, in competition with a more dominant life-form of the shortgrass, the harvester ant.

Cassin’s Sparrows run, walk or hop about as their major mode of movement. Except for the songflight, and the quick flit of surprise, the sparrows are rarely visible. Immature birds in late summer are shyly curious, sitting up a few times in innocent plain sight. On cold winter mornings Cassin’s sparrows greet the sunrise to warm themselves as the heat of the sun increases. But the same field will seem empty of the species at any other time of day.

While the shy Cassin’s sparrow is not well known and only rarely seen, its magic song is the delight of the grasslands of the south central United States and Northern Mexico where it lives.

Nature Notes is sponsored by the Dixon Water Foundation and is produced by KRTS Marfa Public Radio in cooperation with the Sibley Nature Center in Midland, Texas. This episode was written by Burr Williams. Visit sibleynaturecenter.org and join Williams' Facebook page where photos are posted daily.