Vireo atricapillus

The Black-capped Vireo, one of the smallest vireos, is very active but very secretive, making it difficult to detect visually. However, it can be readily located in the breeding season by its distinctive song and other vocalizations. Once seen, the striking black cap and white spectacles framing the red eyes in the adult male distinguishes it from other vireo species. Males in their first breeding season have gray napes and gray extending on to the back of the crown and some may not have any black in the cap (Oberholser 1974).

Black-capped Vireo breeding behaviors, including male participation in incubation and feeding young, make confirmation of nesting or actual nest location relatively easy, with patience. Of the 102 Black-capped Vireo TBBA records 81 (79%) were either confirmed (37 records; 36%) or probable (44 records; 43%) nesting. Thirty-five (80%) of the probable breeding records were based on multiple singing males (23 records; 52%) or evidence of a territory being maintained (12 records; 27%). The remaining 21 records (21%) were possible nestings.

DISTRIBUTION: Black-capped Vireos once nested in scrub-oak habitats from south- central Kansas, through central Oklahoma and central Texas, and into central Coahuila Mexico, and possibly Nuevo Leon and Tamaulipas in Mexico (Graber 1961, Am.Ornithol.Union 1998). Currently Black- capped Vireos nest in the United Sates in central Texas, and three locations in Oklahoma. In Mexico it nests in Coahuila, Nuevo Leon and possibly Tamaulipas (Benson and Benson 1990, Howell and Webb 1995). Little information is available about its nesting status in Mexico or wintering habitat in western Mexico, which ranges from southern Sonora to Guerrero. There are few migratory route records (Grzybowski 1995). TBBA atlasers found Black-capped Vireos in 15 latilongs, confirming nesting in 13 and possible or probable nesting in 2 latilongs. The general distribution of these records closely resembles that of Oberholser (1974).

SEASONAL OCCURRENCE: The Black- capped Vireo is found in Texas only during the breeding season. Black-capped Vireos return to Texas from late March to mid-April and migrate south to Mexico between early August and late September. Breeding may occur from early April to mid-July. TBBA results indicate a breeding season starting later and ending later than recorded by Oberholser. The earliest TBBA nest with eggs (May18) was later than documented by Oberholser (April 20); the July 8 TBBA record of a nest with eggs was also later than Oberholser’s latest recorded nest with eggs (June 26). The earliest TBBA nest with young (May 11) and latest nest with young (July 21) also contrasts with Oberholser’s records of young being fed from April 22 to July 1. The earliest record for a complete clutch is April 4 and the latest nest start is July 21 (USFWS 1991).

BREEDING HABITAT: Known Black-capped Vireo breeding habitat is tied to outcrops of Edwards or Fredericksburg limestone where soils, fire history, and climate interact to produce the preferred vegetation structure. Vegetation in territories is diverse, usually dominated by various oak species with a high density of deciduous plants in the understory, and arranged in clumps with open grassy areas in between (USFWS 1991).Three to five pure white, unmarked eggs are laid in a cup-shaped nest, which hangs from a forked shrub or tree twig, approximately 0.75 to 2.0 m (2-6 feet) above the ground. The nest is built by both the male and female from dried leaves, bark strips, catkins, spider cocoons and held together with spider webs; the nest is lined with fine grasses (Harrison 1979).

STATUS: Although there are no population estimates, there are probably a minimum of 1636 males in Texas (USFWS 1996). Oberholser (1974) documented breeding in 17 Texas counties, and records from 1970-1989 documented Black-capped Vireo occurrences in 40 Texas counties (USFWS 1991). Since 1990, Black-capped Vireos were documented in 27 counties, with uncertain status (no recent sightings or surveys or only historical records) in another 26 counties. Counties with greater numbers (approximately 50-100 or more males) include Bandera, Bell, Burnet, Coryell, Edwards, Kerr, Kinney, Travis, and Val Verde (USFWS 1996).

Following significant reductions in range and numbers, the Black-capped Vireo was federally listed as endangered by the U.S. Fish and Wildlife Service in 1987. The major threats to the species include destruction and modification of nesting habitat, Brown-headed Cowbird parasitism, and possible conversion of its wintering habitat. Protection and management (especially cowbird removal) for Black-capped Vireos is focused on some state and federal lands including Devil’s River, Kickapoo Caverns,  Kerr Wildlife Management Area, Fort Hood, and Balcones Canyonlands National Wildlife Refuge.

By the early 21^st century this vireo in Texas was a rare to locally uncommon summer resident whose range was centered on the southwest Edwards Plateau (Lockwood and Freeman 2004).

Text by L. Karolee Owens (posted with updates 2006)

Literature cited.

American Ornithologists’ Union. 1998. Checklist of North American birds, 7th ed. Am, Ornithol. Union, Washington, DC.

Benson, R H. and K. L. P. Benson. 1990. Estimated size of Black-capped Vireo populations in Coahuila, Mexico. Condor 92:777-779.

Graber, J. W. 1961. Distribution, habitat requirements and life history of the Black-capped Vireo (Vireo atricapillus). Ecol. Monogr. 31: 313-336.

Grzybowski, J. S. 1995 Black-capped Vireo (Vireo atricapillus). in The birds of North America, No. 181 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston MA..

Howell, S. N. G. and S. Webb.. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York.

Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.

Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press, Austin.

U. S. Fish and Wildlife Service. 1991. Black-capped vireo ( Vireo atricapillus) recovery plan. Austin, TX.

U. S. Fish and Wildlife Service. 1996. Black-capped vireo population and habitat viability assessment. Compiled by C. Beardmore, J. Hatfield, and J. Lewis. Report of a September 19-21 workshop. Austin, TX.