Audubon's Oriole

Audubon's Oriole (fmr. Black-Headed Oriole), is a New World passerine inhabiting the forests and thickets of southeastern Texas and the Mexican coast. It is the only species to have a black hood and yellow body. It is divided into four subspecies and two allopatric breeding ranges. The westernmost range extends from Nayarit south to southern Oaxaca, whereas the eastern range stretches from the lower Rio Grande valley to northern Querétaro. Most common in the western range are the subspecies I. g. dickeyae and I. g. nayaritensis; I. g. graduacauda and I. g. audubonii can be found in the eastern range. Like most Central American birds, it is not a migratory species and does not display significant sexual dimorphism. DNA analysis of the ND2 and cyt-b genes strongly suggests that I. graduacauda is most closely related to I. chrysater, the Yellow-backed Oriole.^[1] It is a member of the genus Icterus and therefore should not be confused with the Old World orioles.

Description

The male of the species has a black hood, mandible, and throat, as well as a black tail. Wings are black, but the remiges and retrices (flight feathers) are fringed with white. The secondary coverts form yellow epaulets. The back and vent are yellow washed with olive, and the underside is almost uniformly yellow. Females of this species have a slightly more olive nape and back than the males. The adult female's (first-definitive) plumage is similar to the juvenile plumage; however, unlike adults, the wings are dull brown instead of black. In general, immature specimens have the hood; wingbars; remiges; and epaulets of adult specimens. The first-basic plumage retains the darker, greener coloration of the juvenile plumage, however. Molting generally occurs in early autumn, though some specimens have been noted to molt as early as June.

Behavior

Audubon's Oriole inhabits dense evergreen forests and thickets, preferring riparian (riverside) areas. Though it prefers the shade, mating pairs may occasionally spotted foraging in clearings. In flight, it joins mixed-species flocks that include orioles, jays, tanagers, and other birds of similar size. The nest of the Audubon's Oriole is similar in size and construction to those of the Hooded and Orchard Orioles, being approximately three inches in diameter with a similar depth. The nests are bag-shaped and semi-pensile; that is, they are usually found on the outer twigs of trees, rather than against the trunk. A mating pair of orioles usually incubates two broods per year, each consisting of between three to five eggs per brood; however, chicks hatched from the later brood are usually unable to survive the winter. This species' nests are often parasitized by the Bronzed Cowbird.

Subspecies dickeyae

The subspecies I. g. dickeyae is of note because of the differences in appearance, behavior, and phylogeny between it and the other subspecies of I. graduacauda. The olive wash is weaker, making the bird more proportionally yellow than others of its species. In addition, the yellow epaulets are diminished in dickeyae, being confined to the lesser coverts.

References

Further reading

• Bent, Arthur Cleveland (1965). Life Histories of North American Blackbirds, Orioles, Tanagers, and Allies.. New York: Dover Publications. ISBN 0486210936. 
• Jaramillo, Alvaro; Burke, Peter (1999). New World Blackbirds: The Icterids. Princeton University Press. ISBN 978-0691006802. 
• Peterson, Roger Tory; Chalif, Edward L. (1973). A Field Guide To Mexican Birds. Boston: Houghton Mifflin Company. ISBN 978-0395975145. 
• Stutchbury, Bridget J. M.; and Morton, Eugene S. (2001). Behavioral Ecology of Tropical Birds. San Diego: Academic Press. ISBN 978-0126755565. 
• Baker, Jason M.; López-Medrano, Esteban; Navarro-Sigüenza, Adolfo G.; Rojas-Soto, Octavio R.; and Omland, Kevin E. (2003). The Auk. 
• Flood, N. J., J. D. Rising, and T. Brush. (2002). "Audubon's Oriole (Icterus graduacauda)". In A. Poole and F. Gill, eds. The Birds of North America. Philadelphia, Pennsylvania: The Birds of North America. 
• Flood NJ. (1990). Aspects of the Breeding Biology of Audubon's Oriole. Journal of Field Ornithology. vol 61, no 3. p. 290-302.
• Hobart HH, Gunn SJ & Bickham JW. (1982). Karyotypes of 6 Species of North American Blackbirds Icteridae Passeriformes. Auk. vol 99, no 3. p. 514-518.
• Monk S. G. M.S. (2003). Breeding distribution and habitat use of Audubon's oriole in the Lower Rio Grande Valley of Texas. The University of Texas - Pan American, United States.
• Patrikeev, Michael, Jack C. Eitniear, Scott M. Werner, Paul C. Palmer (2008) Interactions and Hybridization between Altamira and Audubon's Orioles in the Lower Rio Grande Valley Birding 40(2):42-6