Worthen's Sparrow

Taxobox
name = Worthen's Sparrow
status = EN | status_system = IUCN3.1


image_width = 250px
image_caption = © Ray Bieber
regnum = Animalia
phylum = Chordata
classis = Aves
ordo = Passerine
familia = Emberizidae
genus = "Spizella"
species = "S. wortheni"
binomial = "Spizella wortheni"
binomial_authority = Ridgway, 1884
range_

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Worthen’s Sparrow, ("Spizella wortheni"), was first described by Ridgway in 1884. "It was named in honor of Charles K. Worthen, an American naturalist and collector of birds for natural history museums."¹ This small bird was listed under the World Conservation Union, (IUCN) red listas endangered in 1994.²

Description

"Spizella wortheni" can range in heights from 12.5-14 cm. It is identifiable by its distinctive head pattern. It has a grey head with a rufous crown, a brown postocular stripe and a pink bill. It has grey-brown upperparts, with dark brown streaks. It has a grey bottom, and dark brown wings and tail. Its wings are "edged paler, with broad whitish to pale buff wing-bar, buffy-rufous tertial and secondary edging, and greyish lesser coverts."³

Juvenile's are characterized by brownish coloration of the head and chest, with dusky streaking on head and dark brown streaking on chest and flanks.

The song is a dry, chipping trill of 2-3 second duration, and is described as a cross between that of the Field Sparrow and Chipping Sparrow.⁴

The species is similar in appearance to the Field Sparrow ("spizella pusilla"). However, they differ in plumage, habitat, and song.

The species nests from May- July, and usually lays 3-4 eggs. Single-species flocks form after the breeding season and are strongly attracted to permanent sources of water.

The species is not migratory, however a few sightings of individuals have taken place throughout the north-west region of Mexico. Only one individual has ever been identified (shot) in North America, and it was by Rieber on June 16, 1884 near Silver City, New Mexico. ¹ This individual, the first of the species to be described, is the type specimen.

Habitat/ Range

Worthen's Sparrow is endemic to North-Eastern Mexico and currently occupies a 25 km² range.³ Populations formerly occurred in Zacatecas, Coahuila, Nuevo León and Tamaulipas, however presently is only known to occur from south-eastern Coahuila to western Nuevo León.⁴

"Spizella wortheni" prefers open, arid shrub-grassland at elevations of 1,200-2,450 m. For foraging, the species prefers open areas with low grasses. For nesting and cover, it usually inhabits low, dense shrubs.

As of 2004, the current population was estimated to be between 100- 120 individuals.³

Threats

The major threat to this species is habitat destruction. The grassland Worthen's Sparrow is specific too has progressively been plowed for agricultural practices and grazing.

Conservation Efforts

Currently there is a conservation effort being coordinated by the Bird Conservation Alliance and other organizations to protect the Saltillo Savanna in Mexico. The program, known as the Mexican Grasslands Appeal, seeks to purchase over convert|1000|acre|km2 of prime grassland habitat to protect and save this last great North American grassland. By protecting this area, the appeal will conserve habitat for the Long-billed Curlew, Worthen's Sparrow, Burrowing Owl, Mountain Plover, Sprague's Pipit, and Ferruginous Hawk.⁵

References

# Terres, John K. The Audubon Society: Encyclopedia of North American Birds. Alfred A. Knopf, New York/ 1982.
# IUCN Red List: "Worthen's Sparrow." http://www.iucnredlist.org/search/details.php/20663/all
# Bird Life International. "Worthen's Sparrow." http://www.birdlife.org/datazone/search/species_search.html?action=SpcHTMDetails.asp&sid=9006&m=0
# Byers, Clive, Urban Olsson and Jon Curson. Buntings and Sparrows: A guide to the Buntings and North American Sparrows. Pica Press, East Sussex, TN. 1995.
# Bird Conservation Alliance. "Project Saltillo." http://www.birdconservationalliance.org/saltillo/Project_saltillo.cfm

See also

* National Geographic" Field Guide to the Birds of North America ISBN 0-7922-6877-6
* Zink, Robert M. and Donna L. Dittman. "Population structure and gene flow in the Chipping Sparrow and a hypothesis for evolution in the genus "Spizella"." 1993. Wilson Bulletin, 105 (3): 399-413.