Cassin’s Kingbird is a locally common and conspicuous breeding flycatcher in northern and central Mexico and the western United States where its patchy distribution is determined by its preferred elevation range.
Because of the close visual resemblance of Cassin’s, Western (T. verticalis), Couch’s (T. couchii), and Tropical (T. melancholicus) kingbirds, TBBA atlasers had to be especially careful in identifying these species. The most useful field marks for identifying Cassin’s Kingbird are a darker gray head (the dark “mask” of other kingbirds is difficult to see), the strong contrast of the white under the eye with the dark above and behind it, the patterned appearance of the folded wing (caused by pale tips and edges of the coverts), and the combination of long wings and short tail (Kaufman 1990, Pyle 1997). These four kingbird species can also be distinguished by voice.
The nests of Cassin’s and Western kingbirds are similar in appearance. Diet and foraging behavior are also similar, so field workers needed to be cautious here, especially at elevations where both species breed.
DISTRIBUTION: ,During the 1987-1992 field work for the TBBA project volunteers found Cassin’s Kingbird breeding in the Trans- Pecos. Most reports (68%) came from 3 latilong blocks: the block with the Davis Mountains, and two immediately east and south. Another 21% of the total came from the Guadalupe Mountains. This confirms the results of Ohlendorf (1974) who found Cassin’s Kingbird to be a highly localized breeder in Texas with almost all reports from Culberson, Jeff Davis, Presidio and Brewster counties. A North American Breeding Bird Survey (BBS) distribution map (Sauer et al. 2005) shows the highest densities of Cassin’s Kingbirds in and around the Davis Mountains and in the Guadalupe Mountains. Much lower densities were found in the Big Bend area.
Birders visiting these areas of western Texas in late spring and early summer should be able to find this species especially at elevations above 1200 m (4,000 ft).
Although most of the breeding population in the United States is in south and central California, Arizona, New Mexico and west Texas, Cassin’s Kingbird also breeds regularly in southern Nevada, southern Utah, southeastern Colorado, southeastern Montana, eastern Wyoming, southwestern South Dakota, and extreme western Kansas and Oklahoma (Tweit and Tweit 2000).
In Mexico, the species breeds at higher elevations of northern Baja California and the mainland south to the Isthmus of Tehuantepec. Cassin’s Kingbirds winter in western Mexico, Baja California and extreme southwest California (Howell and Webb 1995, Tweit and Tweit 2000).
SEASONAL OCCURRENCE: In the Trans- Pecos, spring migration of Cassin’s Kingbird occurs from early April to mid-May with fall departure between mid-August and early October (Oberholser 1974). Near Marathon in Brewster County in 1935, the first migrant was observed on April 18, with a wave arriving May 24 and 25 (Van Tyne and Sutton 1937).
TBBA volunteers found Cassin’s Kingbird breeding in May and June. In August the species disperses to feeding areas and is often seen on fences and utility wires (Ohlendorf 1974). Cassin’s Kingbird is rare in the rest of the western third of Texas and is casual in winter. throughout the state.
BREEDING HABITAT: In Texas Cassin’s Kingbird breeds in a variety of habitats including grassland and grassland associated with shrubs, oaks, or junipers (52%), riparian woodland (24%), desert shrub (12%), pine-oak-juniper (7%), and suburban (5%). Cassin’s Kingbird usually nests at elevations between 1060 and 1820 m (3,500 to 6,000 ft). The mean is 1435 m (4735 ft). The mean for Western Kingbird (in -Pecos Texas) is 1025 m (3382 ft). This difference in nesting elevation, which reflects habitat preferences, appears to be the major factor separating these species ecologically (Ohlendorf 1974).
In Big Bend National Park, Wauer (1996) reported Casein’s Kingbird sometimes nests in riparian habitat. Ohlendorf (1974) found a nest in the Big Bend area below 760 m (2500 ft) elevation, about 450 m (1500 ft) lower than the lowest of the other 41 nests he found in Texas. TBBA atlasers found breeding evidence along the Rio Grande River west of Big Bend National Park.
Of the 42 nests found by Ohlendorf (1974), 50% were on utility poles or in planted trees. Nests were most often in the upper third of the tree canopy with a mean height of 8.8 m (29 ft). Cassin’s Kingbird nests are large bulky structures, built of a variety of plant materials, usually placed well out on a limb. Dimensions: 20 cm (8 in) outside diameter and 7.6 cm (3 in) high. The cavity averages 9 cm (3.5 in) in diameter and 4.5 cm (1.8 in) deep (Harrison 1979).
A clutch usually has 3-4 eggs. The female incubates for 12-14 days and the young birds fledge about two weeks later (Bendire 1895).
STATUS: Lockwood and Freeman (2004) report Cassin’s Kingbird as an uncommon to locally common summer resident at mid- to upper elevations in the Trans-Pecos region. TBBA workers found most breeding in the state occurred in the area around the Davis Mountains. BBS data indicate 10-30 kingbirds per 40 km (25 mi) route were detected in and around the Davis Mountains (Sauer et al. 2005).
Comparison of the TBBA map with that in Ohlendorf (1974) suggests the breeding range of Cassin’s Kingbird in Texas has not changed in recent years. BBS data for 1966-2004 do not show statistically significant trends for this species in Texas (95% confidence range of -13.4 to 3.1%) from 16 routes suggests more data is needed. In the United States as a whole the interval of -2.4 to 2.2% (from 166 routes) suggests a relatively stable population. (Sauer et al. 2005). The presence of suitable breeding habitat in Guadalupe Mountains National Park and Davis Mountains State Park may assure the future of Cassin’s Kingbird as a breeding species in Texas for now.
Text by Robert C. Tweit.(2006)
Bendire, C. E. 1895. Life histories of North American birds. U. S. National Museum Bulletin, No. 3.
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.
Kaufman, K. 1990. A field guide to advanced birding. Houghton Mifflin, Boson MA.
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.
Ohlendorf, H. M. 1974. Competitive relationships among kingbirds (Tyrannus) in Trans-Pecos Texas. Wilson Bull. 86: 357-373.
Pyle, P. 1997. Identification guide to North American birds, Part 1. Slate Creek Press, Bolinas, CA.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2004. Version 2005.1. USGS Patuxent Wildlife Research Center, Laurel MD (Web site, http://www.mbr-pwrc.usgs.gov/ebbs).
Tweit, R. C. and J. C. Tweit. 2000. Casein’s Kingbird (Tyrannus vociferans). In The birds of North America, No. 534 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Van Tyne, J. and G. M. Sutton 1937. The birds of Brewster County, Texas. University of Michigan Press, Ann Arbor.
Wauer, R. 1996. A field guide to birds of the Big Bend, 2nd ed. Gulf Publishing, Houston, TX.