Rare Sparrow Nests in Arizona Desert Grasslands - 2005
by George C. West
From late May through September, visitors driving up Whitehouse Canyon Road on their way to Madera Canyon may hear a bird song that sounds like a bouncing ball. The song, which lasts three to five seconds, begins with four harsh, high-pitched chips that are followed by about 15 high tseet notes that start slow and speed up like a ping-pong ball bouncing to a stop on a table top. The song concludes with two long, high tsip notes. The singer is a relatively large and very drab sparrow – Botteri’s Sparrow – most often seen perched on an ocotillo stalk, yucca, or mesquite in the middle of the desert grassland (see painting below).
Botteri’s Sparrow is primarily a Mexican bird that enters the United States only in southeastern Arizona, a small area of southwestern New Mexico, and extreme southeastern Texas. In Arizona, Botteri’s Sparrows inhabit desert grassland savanna and, less frequently, oak woodland surrounded by grasses – preferably Giant Sacaton (Sporobolus wrightii) – at elevations between 3,500 and 5,000 feet. Before 1900, this bird was fairly common in the Arizona grasslands, but its numbers decreased with the increase in cattle grazing and other human development. None at all were found in the state in surveys from 1903 to 1932.
Botteri’s Sparrows are dependent on large stands of very tall bunch grasses that provide cover for their nests that are placed on the ground. They also nest in smaller numbers in higher-elevation grasslands dominated by invasive grasses (e.g., Lovegrass - Eragrostis lehmanniana) with scattered brush such as mesquite and acacia. They do tolerate some grazing and occasional burning of the grasslands after the breeding season.
Botteri’s Sparrow was discovered by Matteo Botteri, a Croatian explorer and scientist who had come to Mexico primarily to collect plants. He collected the first specimen in 1857 near Orizaba, Veracruz.
Botteri’s Sparrow is a member of the genus Aimophila,a poorly understood group of sparrows of which 12 species are recognized from Mexico and the United States. Of the 12, six occur in the United States and five of these in Arizona. The only one that looks much like Botteri’s Sparrow is Cassin’s Sparrow. Cassin’s is also a grassland resident, but in general prefers brushier habitats than Botteri’s. The songs of the two species are completely different. Cassin’s usually sings a more complex song with a pronounced up-down or down-up cadence at the end. The song is often given while the bird flutters in the air, showing off the white tips to the outer tail feathers, a feature that Botteri’s Sparrow lacks.
The sketch shows Botteri’s Sparrow’s large bill and flat head with almost no forehead. The undersides are buffy and unmarked by stripes or streaks. The back is brown with a rusty hue with dark, almost black streaks. The tail is long and all dark brown with no white at the tip. Still, the best clue to the bird’s identity is the distinctive bouncing-ball song.
Botteri’s Sparrows winter in Mexico and return to their Arizona breeding grounds by late May. They wait until the monsoon rains begin before they start nesting, as the rains bring more insect food for the young birds. Their diet consists of insects (86%) and seeds (14%). Nests are made of grasses and shaped like an oven, with the entrance pointing down. They face north-northwest to minimize exposure to the hot sun. The nest is well hidden under overhanging grasses. Two to four eggs are laid, and only one brood is raised per summer. The eggs are incubated for about 12 days by the female, who is often fed by the male. The young leave the nest after about ten days, but cannot fly for another week. Adults molt their body feathers in the summer and their flight feathers after returning to Mexico in September and October.
This summer, as you make the leisurely drive up to Madera Canyon, roll your car windows down and listen to the bird songs. You will hear Botteri’s Sparrow and know that it has survived another year in the precious desert grasslands on the bajada below Madera Canyon.