Spizella wortheni
Although it resembles the more numerous and widely distributed Field Sparrow of the United States, the rare and Endangered Worthen’s Sparrow is restricted to the arid open lands of Mexico’s Chihuahuan Desert, where it times its nesting to the yearly patterns of rainfall. Though it’s not considered a migratory species, the Worthen’s Sparrow tends to wander in search of water and other resources after the nesting season, joining mixed-species flocks of Vesper, Brewer’s, Clay-colored, and Black-throated Sparrows and Western Bluebirds.
As with many other threatened and endangered species, the Worthen’s Sparrow is being squeezed out of its range by unsustainable land use. This is a problem faced by other rare sparrows, including the “Oregon” Vesper Sparrow, the Endangered “Florida” Grasshopper Sparrow, and the “Cape Sable” Seaside Sparrow.
Birds around the world are declining, and range-restricted species such as the Worthen’s Sparrow are facing particularly urgent threats. While all birds are made more vulnerable by the cumulative impacts of threats like habitat loss, it is especially concerning for species with small populations in restricted ranges.
The Worthen’s Sparrow is threatened by the conversion of desert scrub for agriculture, particularly potato farming. This essential habitat has also been reduced by overgrazing and habitat fragmentation.
Global climate change is altering rainfall patterns, which are an essential component of the Worthen’s Sparrow’s breeding cycle. Other extreme weather events brought about by climate change, such as droughts and intense heat waves, could also put this species at risk.
Worthen’s Sparrows can be harmed directly by pesticide poisoning or indirectly due to the loss of their insect prey due to pesticide spraying.
Range-restricted birds such as the Worthen’s Sparrow need concerted help to overcome the urgent threats they face. At ABC, we’re inspired by the wonder of birds and driven by our responsibility to find solutions to meet their greatest challenges. With science as our foundation, and with inclusion and partnership at the heart of all we do, we take bold action for birds across the Americas.
Since 2007, ABC, Southern Wings, the Rio Grande Joint Venture, and our partner in Mexico, Pronatura Noreste, have been working to conserve the Worthen’s Sparrow’s habitat in El Tokio Grassland Priority Conservation Area. To date, more than 140,000 acres have been protected through acquisition or enrolled in conservation agreements.
Coalitions such as the Rio Grande Joint Venture bring together conservation partners to enhance and conserve grasslands and riparian woodland habitats in the Chihuahuan Desert, Tamaulipan Brushlands, and the Gulf Coast Prairie Bird Conservation Regions.
This partnership emphasizes working with landowners and stewards to help sustainably manage these habitats through carefully planned livestock grazing, controlling invasive species, and planting native vegetation.
ABC works with partners at the state and federal levels in the U.S. to call for the regulation or cancellation of the pesticides and toxins most harmful to birds. We develop innovative programs, like working directly with farmers to use neonicotinoid coating-free seeds, advance research into pesticides’ toll on birds, and encourage millions to pass on using harmful pesticides.
The Worthen’s Sparrow is a small, slim, and long-tailed bird. Its pink bill, rusty crown, eyering, and plain undersides resemble a Field Sparrow’s, but it can be distinguished from that species by its plain gray face that lacks a rusty stripe behind the eye and its darker, usually blackish, legs. The sexes are similar. Juvenile Worthen’s Sparrows have dusky brown streaking on the head, chest, and flanks.
Another good identification clue is this species’ limited range in Mexico.
The Worthen’s Sparrow’s song, described as a high-pitched peee churrrr, consists of a lower, slurred first note followed by a dry trill that resembles that of a Chipping Sparrow. Its call note is a high, thin tssip, sometimes repeated rapidly.
Andrew Spencer, XC324260. Accessible at www.xeno-canto.org/324260.
Andrew Spencer, XC324262. Accessible at www.xeno-canto.org/324262.
The Worthen’s Sparrow breeds in weedy, overgrown fields, shrubby desert, and dry grasslands, at altitudes ranging roughly from 4,000 to 8,000 feet. Though Worthen’s Sparrows thrive in overgrown, fallow potato fields, fields that are being actively farmed are not suitable habitats.
Specific Area
Chihuahuan Desert in northeastern Mexico; recorded in eight Mexican states, and currently ranges from Coahuila and Nuevo León, south to Zacatecas and San Luis Potosí.
Range Detail
Although the type specimen of Worthen’s Sparrow was collected from Silver City, New Mexico, in 1884, the species has not been recorded in the U.S. since then. It is an extremely range-restricted species, found only in arid upland grasslands in pockets of northeastern Mexico.
Did you know?
The Worthen’s Sparrow depends upon sufficient rainfall to breed successfully, and likely times its nesting to coincide with the verdant flush following rains.
The petite Worthen’s Sparrow is an unassuming presence on the Chihuahuan Desert plateau, lying low in the short shrubs that dot the open, arid grasslands. After its breeding season concludes, the Worthen’s Sparrow gathers in flocks of 10 to 50 birds, sometimes alongside Vesper, Brewer’s, and Black-throated Sparrows, Horned Larks, and Western Bluebirds.
The Worthen’s Sparrow feeds on the ground or low in shrubs. It will sometimes hawk insects from a perch. Its diet consists mostly of weed seeds in the winter, supplemented with insects, spiders, and moths during the nesting season.
Worthen’s Sparrow pair formation occurs in March, and nesting has been recorded from May through July, usually timed to coincide with seasonal rains. During the breeding season, males sing persistently from a low perch each morning.
The Worthen’s Sparrow’s nest is a cup woven from dry grasses and lined with finer material. The nest is located low in or at the base of a shrub, or on the ground.
The female Worthen’s Sparrow lays a clutch of two to five pale blue eggs with brown mottling. Unfortunately, its nests and young are often predated by snakes and coyotes or sometimes disturbed by livestock.
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