Vireo atricapilla once bred from Kansas through Oklahoma to south-west Texas, USA, into central Coahuila and southern Nuevo Leon, Mexico, wintering in Sinaloa, Nayarit, Jalisco, Colima and possibly Oaxaca, Mexico^1,3,4. In Oklahoma and northern and central Texas, it is now restricted to a few sites, and elsewhere populations are increasingly fragmented¹. The population has declined to c.6,000-10,000 individuals, but numbers for south-west Texas and Mexico are uncertain⁶. This decline is not uniform: numbers are stable in the southern 25-30% of the historic breeding range, and management has arrested declines elsewhere².

The range of V. atricapilla extends from Northern, Western and Central Texas to Northern Mexico. During the summer V. atricapilla breeds primarily in the Edward's Plateau of Central Texas. In the winter (non-breeding season), V. atricapilla can be found in the flatlands and Pacific foothills of Western Mexico (throughout the states of Sonora and Guerrero). (Scott 1987; Tveten 1987)

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) Historical breeding range extended from south-central Kansas south through central Oklahoma and central and western Texas to southern Coahuila, Nuevo Leon, and Tamaulipas, Mexico; the southern portion of this range in Mexico was confirmed by recent surveys (USFWS 2007). Present range extends from Blaine County, Oklahoma (two locations, only one of which [Wichita Mountains] has substantial numbers), south through Dallas, the Edwards Plateau, and Big Bend National Park, Texas, and to southern Coahuila, Nuevo Leon, and Tamaulipas, Mexico (USFWS 2007). Winter range is separate from breeding range and extends from southern Sonora, Sinaloa, and western Durango south through western Mexico to Guerrero and southern Oaxaca, but most birds winter in the northern two-thirds of this area (USFWS 2007).

Coded range extent refers to breeding range.

Historic Range:
U.S.A. (KS, LA, NE, OK, TX), Mexico.

V. atricapilla is the smallest and most distinctly marked of all North American Vireos. This bird is fairly small with an average height of 11 cm and wingspan of 16.5 cm. This bird is unique in that it is the only North American bird to have white spectacles on a jet-black head. The female, however, has more of a slate-gray head coloration. Both males and females have red eyes and yellow to whitish wing bars. These birds are generally olive above and white below with yellow flanks. The female is smaller in size and juveniles are more brown above , rather than olive, and buffy below. Black-capped vireos are also distinctly different from all other New World, neo-tropical Vireos because of their quick action, bold patterns and quick flight. The flight of V. actricapillus is quick, nervous and rarely sustained. (Oberholser 1974; Tveten 1987; Scott1987)

Length: 11 cm

Weight: 9 grams

Adults differ from the solitary vireo in having a darker head (vs. bluish-gray in eastern solitary vireos) and in being smaller, averaging 11 cm long (vs. 14 cm in solitary vireo). Differs from Rocky Mountain solitary vireos and gray vireo in having yellowish flanks (vs. gray or white in the other species). Differs from Bell's vireo in having a darker head and much more distinct spectacles. Immatures are browner above and have a darker head than do other similar vireos.

Habitat and Ecology

Systems

• Terrestrial

In general, black-capped vireos prefer low thickets in scrub-oak woodlands, arid hilly regions and ledges on steep hills near water. It is believed that the largest known concentration of V. atricapilla can be found near Austin, Texas, located in the Edward's Plateau region which encompasses 17 % of the state of Texas. Geographically, this area consists of oak thickets combined with heavy ground cover as well as shallow, rocky canyons that receive abundant, bright sunlight. These places are described as "the hottest places imaginable", for birds at least. (Kutac 1989; Tveten 1987)

Comments: Habitat consists of dense low thickets and oak scrub, mostly on rocky hillsides or steep ravine slopes in rugged terrain (Ehrlich et al. 1992). Nesting occurs in areas with clumps of woody vegetation separated by bare ground, rocks, and/or herbaceous vegetation (USFWS 1987), often in areas with sparse Juniperus.

In Texas and Oklahoma, nesting territories had relatively high densities of deciduous vegetation (primarily oaks) close to the ground and occurred where variation in relative density measures of woody vegetation was highest (Grzybowski et al. 1994). Vireos avoided higher juniper densities on the Lampasas Cut Plains and more open areas on the Edwards Plateau. Favorable breeding habitat had 35-55% dispersed scrub cover (primarily deciduous) in spatially heterogeneous configurations, with (in most areas) juniper cover well below 10%; however, in the Edwards Plateau region and areas to the southwest junipers may contribute important cover. See Grzybowski et al. (1994) for further details.

In Mexico, this vireo commonly occurs in dense thickets with few spaces between clumps of vegetation (Benson and Benson 1990).

Habitat is naturally maintained by wildfires and grazing animals, which keep vegetation in early successional stage (Matthews and Moseley 1990).

Winter habitat preferences are not well-known, but habitats include semiarid tropical scrub (AOU 1983) and appear to be less specific than in summer (Collar et al. 1992).

Nests are constructed in twig forks of small trees or shrubs (often Quercus or Rhus virens), or in tangles of shrubby growth, usually 0.4-1.3 meters above ground; foliage that extends to ground level is important (USFWS 1987). Males tend to return to their former breeding territory (Ehrlich et al. 1992).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Arrives in Texas nesting range late March through mid-April, in Oklahoma from mid-April to early May (Collar et al. 1992). Migrates south from Oklahoma by late August to September, from Texas by mid-September (Grzybowski 1991, Collar et al. 1992).

Black-capped vireos are active feeders that like to eat insects. Their diet consists primarily of caterpillars and beetles. Young birds seem to prefer spiders as a supplement to their diet while adults prefer berries. Both glean the insects from foliage in a "characteristic pose" of hanging upside down and then fluttering to a lower branch. (Tveten 1987)

Comments: Eats insects (especially caterpillars when available) and spiders, some fruits; forages low in scrubby vegetation. Forages by foliage gleaning, moving rapidly, sometimes hanging upside down (Grzybowski 1991).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: Occurrences have not been circumscribed using standardized criteria, but the species is represented by a substantial number of distinct occurrences (subpopulations). Since this species was listed in 1987, breeding populations have been documented in 49 Texas counties, five Oklahoma counties, and three Mexican states (USFWS 2007).

About 75 percent of the known population occurs on 4 well-surveyed areas in Texas and Oklahoma (USFWS 2007). The other 25 percent occurs in several dozen other locations.

10,000 - 100,000 individuals

Comments: An accounting of the known population since 2000 indicates that over 6,200 black-capped vireo pairs inhabit three counties in Oklahoma, 38 counties in Texas, and three states in Mexico (USFWS 2007). This does not account for additional breeding populations that have been documented since this species was listed in 1987 (e.g., 11 additional counties in Texas and 2 additional counties in Oklahoma) (USFWS 2007), and it does not include an estimate of the population in unsurveyed or inadeqiately surveyed areas (e.g., in Mexico, where available data suggests that the species often attains higher densities than in the U.S. portion of the range) (USFWS 2007).

Maximum longevity: 7 years (wild) Observations: Females normally breed in their first year, while males breed as yearlings. The oldest banded bird was 7 years of age (http://bna.birds.cornell.edu/).

V. atricapilla arrives at its breeding region in early March and has migrated south by late September. The actual breeding begins in mid-April and ends in early August. These birds are monogamous. The nests of the birds can be found in forked twigs of small trees or shrubs, usually 2-6 ft. up (rarely any higher). The actual nest is compact, cup-like and rounded in shape with thick walls. It is composed of leaves, coarse grasses, bark strips, catkins and spiders' cocoons, all bound together and supported with long plant fibers, spider webs and wool. The inside of the nest is lined with finer grasses. The nests are built by both males and females but the majority of the work is done by the female. The nest is built within six to nine days. Females have a clutch size of three to five eggs. The eggs of V. atricapilla are sub-elliptical to long sub-elliptical. On the exterior they are smooth but non-glossy, pure white and unmarked. Once again, black-capped vireos show their uniqueness in that their eggs are unmarked while all other vireos have spotted eggs. The average size of the egg is 18 x 13 mm. Incubation time ranges from 14 -17 days. Both males and females take turns in keeping the clutch warm. When the altricial nestlings hatch, they are naked with yellowish to pink skin. Males bring 75 % of the nestlings' food. They are fed for another four to seven days. The young leave the nest about ten to twelve days after hatching. Black-capped vireos have a success ratio of one to two chicks per two adult pairs. This low success ratio is attributed to female brown-headed cowbird nest parasitism. (Ehrlich et al 1988; Baicich & Harrison 1997; Tveten 1987, Oberholser 1974)

Complete clutches have been found as early as early April, but most nesting begins around mid- to late April, extends into August, with occasional broods still attended by adults into early September; most nesting is over by late July (Grzybowski 1991). Clutch size 3-5 (usually 4). Incubation 14-17 days, by both sexes. Young tended by both parents, leave nest at about 10-12 days. Parental care may last 30-50 days. Female may renest after first brood fledges, leaving male to care for the first brood. Common host of brown-headed cowbird, which may greatly reduce nesting success.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 1
Species With Barcodes: 1

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2004
  Vulnerable
• 2000
  Vulnerable
• 1996
  Endangered
• 1994
  Endangered

In October of 1987 the U.S. Fish and Wildlife Service placed V. atricapilla on the endangered species list. These birds face extinction primarily because of nest parasitism by female brown-headed cowbirds. it is believed that up to 90 % of black-capped vireos' nests are infected by these brood parasites. The actual process shows that in most cases the female parasite will actually remove the hosts' eggs from an untended nest and then deposit her own. Even if the hosts' eggs are not removed, the vireos still have great odds against survival due to the fact that the incubation period of the brown-headed cowbird is shorter (10 - 12 days) than the Black-capped vireos (14 - 17 days). The hosts' eggs still have even greater odds against their survival if they do hatch because they rarely can compete for nest space and food with the older and larger cowbird hatchlings.

In addition, severe habitat loss, due to urbanization and over-browsing by animals, adds to the susceptibility to extinction of V. atricapilla. Before the 1950's, V. atricapilla was found in Kansas and Oklahoma, as well as in Texas. The last reported sighting of V. atricapilla in Kansas was in 1953.

Fortunately, habitat management and conservation is taking place at many Texas state parks and recreation areas in order to preserve the remaining and dwindling population. Also extermination, of some of the plentiful, brown-headed cowbird populations that take part in nest parasitism which in turn affects the reproductive success of the black-capped vireos, is currently taking place.

(Tveten 1987; Perrins & Middleton 1985; Robbins, Brunn & Zim 1983)

US Federal List: endangered

IUCN Red List of Threatened Species: vulnerable

United States

Rounded National Status Rank: N2B - Imperiled

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Small breeding range in the south-central U.S. and adjacent northeastern Mexico; northernmost breeding populations extirpated, but known range has increased in the south as a result of recent surveys; known population size is more than 6,200 pairs, and total population size may be much larger than this; population trend is not well known but population size appears to have increased in some areas; threats include habitat loss and degradation resulting from fire supression and effects of ungulates, and cowbird parasitism; better information is needed on distribution and abundance in Mexico.

Current Listing Status Summary

Status: Endangered
Date Listed: 10/06/1987
Lead Region:   Southwest Region (Region 2) 
Where Listed:


Population detail:

Population location: entire
Listing status: E

For most current information and documents related to the conservation status and management of Vireo atricapilla , see its USFWS Species Profile

Population

Population Trend

Global Short Term Trend: Unknown

Comments: Overall trend is not well known. Known breeding populations in three of the four areas with the most intensive survey efforts have increased almost 10-fold since surveys were reported in 1996; these include Fort Hood Military Reservation (Texas), Wichita Mountains Wildlife Refuge (Oklahoma), and Fort Sill Military Reservation (Oklahoma) (USFWS 2007). Probably at least part of this increase reflects a true population increase (versus an increase resulting from increased survey effort) (USFWS 2007)

Trends in breeding habitat are unknown. but a crude measure of potential habitat change for 1992-2002 suggests that the amount of potential habitat decreased during that period in Texas but not in Oklahoma (USFWS 2007).

The dynamic nature of the habitat of this species suggests that local populations may fluctuate as habitat suitable changes; some populations may become extirpated while new ones become established in other areas.

Global Long Term Trend: Increase of 10-25% to decline of 50%

Comments: Northernmost breeding populations have been extirpated; the species has not been detected in Kansas since the 1950s (USFWS 2007).

Major Threats

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: Threats include cowbird parasitism (locally may affect 80-100% of nests in most years) and the loss of nesting habitat (due to housing development and road construction; over-browsing by domestic livestock, exotic ungulates (e.g., axis deer, blackbuck antelope, aoudad, fallow deer, and sika deer), and white-tailed deer; vegetation maturation resulting from fire suppression; and range management practices that remove broad-leaved, low woody vegetation).

Habitat alteration by invasive junipers appears to be a major limitation in the maintenance and development of suitable breeding habitats in many portions of the range (USFWS 2007). Juniper invasion into suitable habitats appears to be a function of the combined influence of fire suppression and overgrazing, and it may be further influenced by drought (USFWS 2007). The threat of vegetational succession, particularly invasion by Ashe juniper, is complicated by the requirement of mature oak-juniper woodlands by the endangered golden-cheeked warbler.

Available evidence indicates that extremely high stocking rates of herbivores (especially goats, white-tailed deer, and exotic ungulates) can degrade black-capped vireo breeding habitat. When grazing pressure is reduced, the breeding habitat may recover under some conditions (USFWS 2007).

The density and abundance of domestic livestock, particularly goats, have declined substantially in those regions where this threat was of greatest concern at the time of listing, primarily in the Edwards Plateau and Southwest and Trans-Pecos Regions (USFWS 2007). In contrast, the density and abundance of white-tailed deer and exotic herbivores may have increased in those regions of greatest concern at the time of listing, particularly in the Edwards Plateau of Texas (USFWS 2007).

The threat posed by brood parasitism throughout major portions of the range in Texas has likely lessened since the species was listed, due to a combination of an apparent decrease in cowbird abundance, an apparent increase in black-capped vireo populations, and circumstantial evidence of a reduction in parasitism rates at some locations due to cowbird removal (USFWS 2007). This same threat essentially remains unchanged since the time of listing throughout the species' range in Oklahoma (USFWS 2007).

Red imported fire ants have increased in distribution and abundance since the black-capped vireo was listed, these prey on vireo eggs/young and likely pose an increasing threat (USFWS 2007).

Conservation Actions

Management Requirements: Beneficial management activities include removal of cowbirds from nesting areas; cowbird removal has been a successful technique, but presently it benefits only a small portion of the total population (Grzybowski 1991).

Hot fires and bulldozers can be used to create favorable habitat conditions (Grzybowski 1991). Prescribed fire is an important tool in maintaining habitat suitability in Oklahoma and in the eastern portion of the species' range in Texas, whereas in the western portion of the breeding range in Texas and in Mexico, fire is not as important in maintaining habitat suitability (USFWS 2007).

See also USFWS (1987), Grzybowski et al. (1994), and habitat comments for information on habitat management and other management issues.

Biological Research Needs: Better information is needed on the magnitude and trends of brood parasitism by the brown-headed cowbird, as well as differences in parasitism rates across the breeding range (USFWS 2007).

Global Protection: Several (4-12) occurrences appropriately protected and managed

Comments: Protected areas include the Balcones Canyonlands National Wildlife Refuge (80-100 pairs), Santa Ana National Wildlife Refuge, and Wichita Mountains National Wildlife Refuge.

Economically, the decline in the population of the black-capped vireo has had a negative impact on humans in terms of restrictions on urban growth and development needed to meet the expanding demographics of the Central Texas area.

Stewardship Overview: Recovery plan is out-of-date and needs to be updated (USFWS 2007).

Recvoery depends on management to reduce major threats (loss of habitat and brood parasitism). Conservation programs and measures implemented to reduce the threats to the species include a 37-county Safe Harbor Agreement, private lands incentives, cowbird removal programs, and public outreach. Most of these measures have occurred within the species' range in Texas (USFWS 2007).

Comments: Vireo atricapilla and V. nelsoni may constitute a superspecies (AOU 1998).