Spizella wortheni

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	PASSERIFORMES	EMBERIZIDAE

Scientific Name:

Spizella wortheni

Species Authority:

Ridgway, 1884

Common Name/s:

English

–

Worthen's Sparrow

Assessment Information [top]

Red List Category & Criteria:

Endangered B1ab(i,ii,iii,v);C2a(i);D ver 3.1

Year Published:

2008

Assessor/s:

BirdLife International

Reviewer/s:

Mahood, S., Butchart, S.

Contributor/s:

Howell, S., Cruz-Nieto, M.

Justification:
This species has an extremely small and declining range and population, and fledging success is very low, but it qualifies as Endangered (rather than Critically Endangered) because it breeds at three sites and at least one subpopulation is larger than 50 individuals.

History:

2004	–	Endangered
2000	–	Endangered
1996	–	Endangered
1994	–	Endangered

Geographic Range [top]

Range Description:	Spizella wortheni has suffered a major range contraction and currently only breeds at sites in Coahuila and Nuevo León: La India (where discovered in 2004)⁴, San Jose del Alamito⁷ and Tanque de Emergencia (100-120 individuals found in January 1998²) in Coahuila. In Nuevo León it breeds in Las Esperanzas^1,3, Carbonera^6,7. Wintering flocks have been observed in Erial (100 individuals observed in February 2006), Carbonera, San Rafael in Nuevo Leon, In Coahuila in Rancho Los Angeles (60 individuals were observed in February 2006)^6,7. Thorough surveys may find additional sites because suitable habitat remains within its historical range⁸. It was first described from New Mexico, USA in 1884, but it has only been recorded in Mexico since that date³. There are records from eight states, but it was last recorded in Puebla in 1893, Tamaulipas in 1924, San Luis Potosí in 1951, Veracruz before 1957, Chihuahua in 1959 and Zacatecas in 1961³. The few records from San Luis Potosí, Zacatecas, Puebla and Veracruz were in the non-breeding season, and may refer to migrants, isolated individuals or extirpated populations. However, since birds move only locally in the non-breeding season in Coahuila and Nuevo Leon and there has been a large breeding range contraction in the north, it seems more likely that these represent extirpated populations³.
Countries:	Native: Mexico
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	S. N. G. Howell in litt. (1998)
Population Trend:	Decreasing

Habitat and Ecology [top]

Habitat and Ecology:	It is confined to open, arid shrub-grassland at elevations of 1,200-2,450 m ^1.3 where breeding sites have been found in associations of tarbush (Flourensia cernua), creosotebush (Larrea tridentata), Fourwing saltbush (Atriplex canescens) and short grassland^4,6. It probably keys-in on certain vegetational structural components, such as open areas with low (grazed) grasses for foraging and a moderate complement of low, dense shrubs for cover and nesting^1,4,6. Taller shrubs and trees may serve as observation or song perches, but a lack of shrubs over 0.5 m is not a deterrent to habitat occupancy¹. There are indications that it prefers the open-wooded area ecotone, but this is not the case at Las Esperanzas^1,3. In recently discovered breeding areas, 57 characterized nests showed a preference for tarbush as a nesting shrub (63%) followed by Opuntia spp (25%), tarbush-Opuntia spp (7%), allthorn (Koeberlinia spinosa;3%) and Berlandier wolfberry (2%)⁷. Nests of 3-5 eggs have been found in May-August^4,6. Single-species flocks form after the breeding season³ and are apparently strongly attracted to permanent water¹.
Systems:	Terrestrial

Habitat and Ecology:

It is confined to open, arid shrub-grassland at elevations of 1,200-2,450 m ^1.3 where breeding sites have been found in associations of tarbush (Flourensia cernua), creosotebush (Larrea tridentata), Fourwing saltbush (Atriplex canescens) and short grassland^4,6. It probably keys-in on certain vegetational structural components, such as open areas with low (grazed) grasses for foraging and a moderate complement of low, dense shrubs for cover and nesting^1,4,6. Taller shrubs and trees may serve as observation or song perches, but a lack of shrubs over 0.5 m is not a deterrent to habitat occupancy¹. There are indications that it prefers the open-wooded area ecotone, but this is not the case at Las Esperanzas^1,3. In recently discovered breeding areas, 57 characterized nests showed a preference for tarbush as a nesting shrub (63%) followed by Opuntia spp (25%), tarbush-Opuntia spp (7%), allthorn (Koeberlinia spinosa;3%) and Berlandier wolfberry (2%)⁷. Nests of 3-5 eggs have been found in May-August^4,6. Single-species flocks form after the breeding season³ and are apparently strongly attracted to permanent water¹.

Systems:

Terrestrial

Threats [top]

Major Threat(s):	Open shrub-grasslands have been greatly reduced by agriculture and grazing, and the rate of habitat conversion is increasing, primarily for production of potatoes⁸. There has been a progressive loss of habitat even on the Coahuila-Nuevo León border, especially in the El Potosí valley⁸. Grazing and the use of chemicals modify and reduce the quality of the habitat and disturb nesting birds⁴. It seems unlikely that large tracts of habitat remain near the currently known sites^3,4,6. Reported reproductive success is very low, only 14% in la India and 0% in Carbonera, predation^4,6 and livestock disturbance⁶ seems to be the main cause but it is not known how this affects populations⁴. Snakes and Coyotes are thought to predate nests⁸.

Major Threat(s):

Open shrub-grasslands have been greatly reduced by agriculture and grazing, and the rate of habitat conversion is increasing, primarily for production of potatoes⁸. There has been a progressive loss of habitat even on the Coahuila-Nuevo León border, especially in the El Potosí valley⁸. Grazing and the use of chemicals modify and reduce the quality of the habitat and disturb nesting birds⁴. It seems unlikely that large tracts of habitat remain near the currently known sites^3,4,6. Reported reproductive success is very low, only 14% in la India and 0% in Carbonera, predation^4,6 and livestock disturbance⁶ seems to be the main cause but it is not known how this affects populations⁴. Snakes and Coyotes are thought to predate nests⁸.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway The north side of the valley near at Tanque de Emergencia (Rancho Los Angeles), is managed appropriately by the Universidad Autónoma Agraria Antonio Narro (UAAAN), using a rotational grazing regime to ensure that the grass is always high in several pastures³. The India locality has been proposed as a protected natural area within the category of Sanctuary by the Museo de las Aves de Mexico, Saltillo. Pronatura Noreste have fenced an important winter foraging locality for this species⁸. Conservation Actions Proposed Survey to identify additional breeding sites. Monitor known populations. Assess precise ecological requirements and understand local movements⁴. Implement rotational grazing regimes at known sites³. Identify main predators and their impact over the reproductive success of the species⁴. Develop an environmental education program to promote the value of the ecosystem⁴, and the importance of appropriate grazing regimes.

Conservation Actions:

Conservation Actions Underway
The north side of the valley near at Tanque de Emergencia (Rancho Los Angeles), is managed appropriately by the Universidad Autónoma Agraria Antonio Narro (UAAAN), using a rotational grazing regime to ensure that the grass is always high in several pastures³. The India locality has been proposed as a protected natural area within the category of Sanctuary by the Museo de las Aves de Mexico, Saltillo. Pronatura Noreste have fenced an important winter foraging locality for this species⁸.

Conservation Actions Proposed
Survey to identify additional breeding sites. Monitor known populations. Assess precise ecological requirements and understand local movements⁴. Implement rotational grazing regimes at known sites³. Identify main predators and their impact over the reproductive success of the species⁴. Develop an environmental education program to promote the value of the ecosystem⁴, and the importance of appropriate grazing regimes.

Citation:	BirdLife International 2008. Spizella wortheni. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 24 May 2012.
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