Birdfinding.info ⇒ Common and conspicuous across most of its range. Often found around livestock and in various human-altered habitats. Rare in the U.S. An apparent invasion lasted from the late 1980s into the ‘90s, with a slew of records that spread from southern Florida to many other eastern states. Areas where it has been found consistently include: the western coast from Tampa Bay to Fort Meyers; the Belle Glade area; Homestead; Flamingo (Everglades National Park); and the lower keys from Marathon to Key West.
Shiny Cowbird
Molothrus bonariensis
South America, the West Indies, and expanding into the U.S. and Central America.
Common and widespread in open, lightly wooded, and settled habitats, including agricultural areas and towns. A brood parasite that has been observed targeting at least 201 species. It is implicated in the declines of several species, especially in the West Indies.
Occurs nearly throughout South America except in high mountains, barren deserts, subantarctic steppes, and extensive unbroken forest. Also throughout most of the West Indies, but absent from many of the smaller and drier islands. In Central America, it occurs north at least to Nicaragua’s southern border.
In North America, resident in southern Florida, sporadic along the Gulf Coast to Louisiana, casual to coastal Texas and North Carolina, and accidental north to Michigan and New Brunswick.
Historically limited to South America and Trinidad & Tobago, but its range has gradually expanded north and west across the West Indies and Central America since the 1890s, starting in the Lesser Antilles. It reached Puerto Rico in 1950s, Hispaniola in the 1970s, and Cuba and Florida in the 1980s.
Within South America, it continues to expand into human-altered habitat, filling in previous gaps in Amazonia, along the Pacific Coast, and locally up into the Andes.
Identification
Male is all-black with a glossy sheen that is purplish on the head, neck, breast, and back, and becomes bluish, then greenish, on the wings and tail.
Shiny Cowbird, male. (Delta del Paraná, Buenos Aires, Argentina; September 20, 2015.) © Diego Marino
Shiny Cowbird, male. (Puembo Birding Garden, Pichincha, Ecuador; June 12, 2015.) © Jon Lowes
Shiny Cowbird, male showing the progression of its glossy sheen from purplish to bluish to greenish. (San Isidro, Lima Peru; August 3, 2018.) © Mercedes Benavides
Shiny Cowbird, male showing the progression of its glossy sheen from purplish to bluish to greenish. (Rancho Vegas, Cayey, Puerto Rico; April 29, 2018.) © José Santiago
Shiny Cowbird, male striking a typical posture of alertness. (Torry Island, Belle Glade, Florida; July 16, 2016.) © Kenny Miller
Shiny Cowbird, male. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; August 7, 2010.) © Jose Luis Merlo
Shiny Cowbird, male in low light, but still showing purplish and bluish sheen. (Las Terrazas, Sierra del Rosario Biosphere Reserve, Artemisa, Cuba; January 11, 2016.) © Michael J. Good
Shiny Cowbird, male showing that it does not always shine. (La Planicie, Lima, Peru; January 31, 2011.) © Stephen Gast
Shiny Cowbird, male showing narrow, elongated head shape and bulky body—in strong light, the wings often appear brighter than the body. (Tierra del Sol Golf Course, Aruba; April 9, 2013.) © Steven Mlodinow
Shiny Cowbird, male showing narrow, elongated head shape and bulky body. (San Sebastián de la Selva Private Reserve, Misiones, Argentina; October 8, 2012.) © Luis Cesar Tejo
Shiny Cowbird mating ritual. © Román Montero
Female plumage is nondescript and highly variable, with no prominent or distinctive features. When no males are present, the identification of females is often based on size, bill shape, and process of elimination.
Its overall coloration is drab: some shade of brown, usually grayish, and somewhat darker and browner on the wings and tail. The body plumage can be even-toned or subtly spotted or streaked.
Shiny Cowbird, female showing typically drab coloration and a distinct brow. (Homestead, Florida; June 10, 2017.) © Shane Runyon
The predominant tone varies from pale sandy to gray to warm-brown to olive-gray to dark brown. A blackish morph occurs from southern Brazil into Argentina.
Shiny Cowbird, female with typical coloration and a distinct brow. (Tunapuna-Piarco, Trinidad; May 18, 2017.) © Mike Hudson
Shiny Cowbird, female. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; September 23, 2017.) © J. Simón Tagtachian
Shiny Cowbird, female showing pale sandy coloration and a short brow. (Mondesir, Siparia, Trinidad; February 3, 2018.) © Tarran Maharaj
Shiny Cowbird, female, blackish morph, with a distinct brow. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; November 29, 2015.) © Eduardo Cusano
Shiny Cowbird, female showing warm-brown coloration with subtle streaks and a vaguely defined brow. (Vicente López Ecological Reserve, Buenos Aires, Argentina; May 11, 2019.) © Jorge La Grotteria
Shiny Cowbird, female with olive-gray coloration and no distinct features. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; September 8, 2018.) © Ezequiel Vera
Most females have a pale brow, although it is usually subtle. It is often most pronounced directly over the eye, where it narrows and curves to trace an arc along the upper edge of the eye. Behind the eye, the brow typically broadens—however, many individuals have a short brow, and some lack it altogether.
The face is usually dark between the brow and throat, giving it a slightly masked appearance.
Shiny Cowbird, female with pale gray coloration and a distinct long brow. (St. George, Grenada; January 18, 2018.) © Knut Hansen
Shiny Cowbird, female, with pale gray, spotty plumage and a distinct narrow brow—riding a horse. (Estero Mantagua, Valparaíso, Chile; December 3, 2017.) © Renacer Experimental
Shiny Cowbird, female with warm-brown coloration, an indistinct brow, and noticeable mask. (Fruitville, Florida; June 4, 2015.) © Randy Harrod
Shiny Cowbird, female with an aberrant (pale and rounded) bill and a prominent but short pale brow. (Divi Village Golf Course, Aruba; April 14, 2017.) © Steven Mlodinow
Shiny Cowbird, female, paler and spottier than most, with a distinct long brow and darker cheek. (San Isidro, Lima, Peru; February 16, 2019.) © Rutger Koperdraad
Shiny Cowbird, female with warm-brown coloration and a distinct short brow. (Bubali Bird Sanctuary, Aruba; July 20, 2017.) © Michiel Oversteegen
Shiny Cowbird, female, blackish morph, with a distinct, but very narrow and short brow. (Parque Germânia, Rio Grande do Sul, Brazil; November 26, 2016.) © Paulo Krieser
Shiny Cowbird, female, a dark individual with a noticeable brow. (Delta del Paraná, Buenos Aires, Argentina; September 20, 2015.) © Diego Marino
Many females have no noticeable facial markings and are essentially featureless brownish birds.
Shiny Cowbird, female with grayish-brown coloration and no distinct features. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; June 3, 2017.) © Ricardo A. Palonksy
Shiny Cowbird, female with dark-brown coloration and no distinct features. (Vitacura Bicentennial Park, Santiago, Chile; February 16, 2018.) © Maria Antonieta Gonzalez Soto
Shiny Cowbird, female, blackish morph, with a subtle short brow. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; January 1, 2018.) © J. Simón Tagtachian
Shiny Cowbird, female showing typical coloration and an indistinct brow. (Bubali Bird Sanctuary, Aruba; April 7, 2013.) © Steven Mlodinow
Shiny Cowbird, female with grayish-brown coloration and no distinct features. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; July 9, 2018.) © J. Simón Tagtachian
Shiny Cowbird, female with medium-brown coloration and no distinct features. (Lake Apopka Wildlife Drive, Apopka, Florida; June 5, 2016.) © Paul Hueber
Immatures generally resemble females, but typically show more uneven coloration and often more contrast between the upperparts and underparts. Most show distinct streaking on the body.
Juveniles in particular are heavily streaked, especially on the underparts, and sometimes suffused with a patchy yellowish wash.
Shiny Cowbird, probably immature—note heavily streaked body and chestnut in flight feathers. (San Miguel del Monte, Buenos Aires, Argentina; January 25, 2015.) © Hernán Tolosa
Shiny Cowbird, immature—note streaked underparts and warm-brown in flight feathers. (La Rioja, Argentina; November 30, 2015.) © Carlos De Biagi
Shiny Cowbird, juvenile—note heavily streaked underparts and yellowish wash. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; December 6, 2015.) © Eduardo Cusano
Shiny Cowbird, juvenile showing extensive yellowish wash. (Barrio Naranjo, Comerío, Puerto Rico.) © Ernesto Burgos
Immature males go through an obvious transition to adult plumage as irregular patches of black feathers emerge.
Shiny Cowbird, immature male—note isolated black feathers on the lower back—with immature House Sparrow at left. (Rancho Vegas, Cayey, Puerto Rico; June 24, 2018.) © José Santiago
Shiny Cowbird, male, immature beginning molt into adult plumage—note isolated black feathers on the breast. (Costanera Sur Ecological Reserve, Buenos Aires, Argentina; January 5, 2019.) © Dolores Fernandez
Shiny Cowbird, male molting into adult plumage. (Rancho Vegas, Cayey, Puerto Rico; July 9, 2017.) © José Santiago
Shiny Cowbird, male molting into adult plumage. (Vitacura Bicentennial Park, Santiago, Chile; March 11, 2015.) © Vicente Pantoja Maggi
Cf. Brown-headed Cowbird. Female Shiny and Brown-headed Cowbirds can be extremely difficult to distinguish in the field. Both species are variable enough to overlap in most features and some individuals are atypical of their species. Some tendencies that may be helpful include:
Body Plumage: Most female Brown-headed Cowbirds have a spotty appearance above and below, with feathers that have darker centers and paler edges. Female Shiny’s plumage is usually more uniform, especially on the back.
Facial Pattern: As a rule of thumb, female Shiny Cowbird shows a more pronounced, narrow eyebrow that curves over the eye. Female Brown-headed shows a more noticeably pale, whitish throat that is framed by dark malar stripes, and its face is paler, which makes its eye appear more prominent. Some female Brown-headed Cowbirds have a noticeably pale head—echoing the male’s pattern—which is diagnostic for those individuals.
Structure: On average, Brown-headed has shorter, stouter bill, shorter tail, and longer wings. Shiny is slimmer-looking, closer to the shape of a blackbird, with a more typically icterid bill.
Bill Color: Female Shiny Cowbird’s bill is almost always all-black or blackish, whereas female Brown-headed’s bill is usually paler, especially toward the base of the lower mandible.
Cf. Screaming Cowbird. Screaming Cowbird (both sexes) is similar to the male Shiny Cowbird, but not as shiny, with a duller, uniformly bluish sheen. Screaming has a shorter bill, shorter tail, and longer wings.
Notes
Polytypic species consisting of seven recognized subspecies.
References
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Peru Aves, Shiny Cowbird (Molothrus bonariensis), http://www.peruaves.org/icteridae/shiny-cowbird-molothrus-bonariensis/.
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