Icterus chrysater
yellow-backed oriole

Yellow-backed orioles (Icterus chrysater) are found in three allopatric populations (Jaramillo and Burke, 1999). The southern population, Icterus chrysater giraudii, is endemic to northern Venezuela and Panama, stretching east through Colombia to the Gulf of Mexico (Ridgely and Tudor, 1989). In Colombia, this species’ range is restricted by two mountain ranges, the Andes forming the western boundary and the Macarenas forming the eastern boundary (Ridgely and Tudor, 1989). (Jaramillo and Burke, 1999; Ridgely and Tudor, 1989)

Subspecies I. c. chrysater and I. c. mayensis are endemic to Central America. They are widely disjunct from the South American population. Icterus chrysater chrysater is found throughout northern Central America (Jaramillo and Burke, 1999). Its range extends from Nicaragua west to the eastern border of Oaxaca, and from the Gulf of Mexico south nearly to the Pacific Ocean (Jaramillo and Burke, 1999). Although I. c. chrysater exists in several disjunct regions in Central America, these regions are not separated widely enough and the local populations are not genetically distinct enough to be classified as separate subspecies. The other subspecies, Icterus chrysater mayensis, is restricted to the Yucatan peninsula (Jaramillo and Burke, 1999). (Jaramillo and Burke, 1999)

A fourth subspecies, Icterus chrysater hondae, has been proposed, which would also occupy the South American part of this species’ range (American Ornithologists Union, 1998). However, support for I. c. hondae is based on two specimens of I. chrysater taken from Colombia’s Upper Magdalena Valley, so it is possible that I. c. hondae and I. c. giraudii are the same subspecies but with markedly different coloration (Jaramillo and Burke, 1999; Ridgely and Tudor, 1989). (American Ornithologists’ Union, 1998; Jaramillo and Burke, 1999; Ridgely and Tudor, 1989)

Yellow-backed orioles are a tropical edge species that prefers scrub forest and open woodlands (Jaramillo and Burke, 1999). Though normally observed in mixed pine-oak woodland, this species may also be observed in cloud forests and on banana plantations (Jaramillo and Burke, 1999; Howell and Webb, 1995). Lowland populations have also colonized deciduous woodland (Ridgely and Tudor, 1989). (Howell and Webb, 1995; Jaramillo and Burke, 1999; Ridgely and Tudor, 1989)

Mexican populations may be found from sea level to 900 meters; Central and South American populations are more common at elevations greater than 900 m (Wetmore et al., 1984). Individuals of I. chrysater have been founding living at elevations of up to 2900 m (Jaramillo and Burke, 1999). (Jaramillo and Burke, 1999; Wetmore, Pasquier, and Olson, 1984)

Yellow-backed orioles are a yellow bodied, nearly monomorphic species; males and females are difficult to tell apart based on plumage coloration. Length measurements range from 20.5 to 24 cm (8 to 9.5 in.) (Howell and Webb, 1995) averaging 21.5 cm (8.5 in.), making Icterus chrysater a medium-sized oriole species (Jaramillo and Burke, 1999). In adult yellow-backed orioles the bill is mostly black and the basal third of the lower mandible appears blue-gray (Jaramillo and Burke, 1999). The feet and legs are also gray, the toes ending in black claws (Wetmore et al., 1984). Though slightly curved, the bill often appears to be straight from a distance (Jaramillo and Burke, 1999). The tail is black, rounded, and graduated (Jaramillo and Burke, 1999). (Howell and Webb, 1995; Jaramillo and Burke, 1999; Wetmore, Pasquier, and Olson, 1984)

Adult male yellow-backed orioles have strongly contrasting regions of yellow and black plumage (Ridgely and Tudor, 1989). The bib and face are black, as are the wings, tail, and scapulars. The back and underparts are all a bright golden yellow (Jaramillo and Burke, 1999; Howell and Webb, 1995). Excluding the belly and undertail coverts, those parts that appear bright yellow on males of this species are tinged green in females (Jaramillo and Burke, 1999). Although there are some differences in coloration between sexes in I. chrysater (Hofmann et al. 2008), sexes may be indistinguishable in the field. (Hofmann, Cronin, and Omland, 2008; Howell and Webb, 1995; Jaramillo and Burke, 1999; Ridgely and Tudor, 1989)

Immature yellow-backed orioles are greener than adult females (Jaramillo and Burke, 1999). In addition, the remiges and retrices (flight feathers) are dull brown, though the coverts are nearly black (Jaramillo and Burke, 1999). Juveniles have similar plumage, but lack the black bib of older yellow-backed orioles (Jaramillo and Burke, 1999). The other distinguishing features occur on the head -- the presence of a bright yellow supercilium and olive lores (Jaramillo and Burke, 1999). (Jaramillo and Burke, 1999)

Several species have plumage patterns resembling those of I. chrysater. The most similar sympatric species is Icterus nigrogularis, informally called the “yellow oriole” (Ridgely and Tudor, 1989). They may be distinguished from I. chrysater by their white-fringed secondaries and tertials and less extensive black bibs (Ridgely and Tudor, 1989). Audubon’s orioles, Icterus graduacauda, are also similar to I. chrysater in appearance, but the two species are allopatric. However, I. graduacauda is greener and, like I. nigrogularis, differs by the presence of wing bars (Jaramillo and Burke, 1999; Howell and Webb, 1995). (Howell and Webb, 1995; Jaramillo and Burke, 1999; Ridgely and Tudor, 1989)

The longevity of this species could not be determined from available information.

Although little has been recorded regarding this species’ behavior, yellow-backed orioles have been seen congregating in pairs or small flocks of 6 to 8 individuals (Wetmore et al., 1984). Flocks of yellow-backed orioles are believed to be family units, as they often include birds with immature plumage in addition to mature adults (Wetmore et al., 1984; Jaramillo and Burke, 1999). Additionally, yellow-backed orioles sometimes join mixed-species flocks, which include band-backed wrens (Camphylorhynchus zonatus), Cyanocorax jays and orioles of similar size (Icterus) (Jaramillo and Burke, 1999; Howell and Webb, 1995). (Howell and Webb, 1995; Jaramillo and Burke, 1999; Wetmore, Pasquier, and Olson, 1984)

Home Range

Due to a lack of information, the home range size of this species is largely unknown.

Yellow-backed orioles primarily communicate using vocalization. Both sexes sing (Jaramillo and Burke, 1999) as is normal for tropical, monomorphic orioles (Price et al., 2007; Price et al., 2009). (Jaramillo and Burke, 1999; Price, Friedman, and Omland, 2007; Price, Lanyon, and Omland, 2009)

Yellow-backed oriole song consists of 4 to 6 clear whistles, the notes acquiring a muddier, warbled quality in the southern part of the species’ range (Jaramillo and Burke, 1999). Vocalizations made by I. chrysater resemble those made by spot-breasted orioles (Icterus pectoralis) (Skutch, 1996) or Audubon’s orioles (Icterus graduacauda) (Howell and Webb, 1995). Yellow-backed orioles normally deliver their songs from high branches (Ridgely and Tudor, 1989) (Jaramillo and Burke, 1999; Ridgely and Tudor, 1989; Skutch, 1996)

In addition to song, I. chrysater exhibits several other vocalizations, many typical to the genus Icterus. Alvaro Jaramillo (1999) describes the primary call as a short “chert”; other calls include a “whistling chatter” (Jaramillo and Burke, 1999) and a “nasal alarm” (Skutch, 1996). (Jaramillo and Burke, 1999; Skutch, 1996)

Yellow-backed orioles are primarily insectivorous, their diet including caterpillars (Lepidoptera), ichneumon wasps, longhorn beetles (Cerambycidae), cistelid beetles (Cistelidae), cockroaches (Blattaria), ants (Formicidae), and weevils (Curculionidae) (Wetmore et al., 1984). They will also consume arachnids and terrestrial mollusks (Wetmore et al., 1984). Bananas are a significant contributor to the yellow-backed oriole diet (Jaramillo and Burke, 1999). This species has been observed consuming nectar, especially from balsa trees (Ochroma pyramidale) and Heliconia (Leck, 1974). Analysis of the stomach contents of two yellow-backed orioles by Leck (1974) revealed that this species augments its diet with seeds (Wetmore et al., 1984; Leck 1972). (Jaramillo and Burke, 1999; Leck, 1972; Wetmore, Pasquier, and Olson, 1984)

Yellow-backed orioles often forage in pairs or small flocks; oftentimes, mated pairs will be seen foraging together (Jaramillo and Burke, 1999). This species acquires food primarily by probing, and is normally seen foraging in pine trees (Jaramillo and Burke, 1999). Members of this species have been observed flaking the bark of pine trees to expose boring insects, as well as probing epiphytes (including bromeliads) for insects (Jaramillo and Burke, 1999). When taking nectar from flowers of Erythrina fusca, they normally visis flowers that are already open, but will also puncture the calices of unopened flowers to gain access to the nectar (Morton, 1979). It is possible that this behavior is not limited to flowers of E. fusca. (Jaramillo and Burke, 1999; Morton, 1979)

The effects of predators on Icterus chrysater populations are not well known, but it may be assumed that possible predators of this species are similar to those of related orioles and may include snakes, ants, and some jays and crows.

This species plays a role in the regulation of several insect and arthropod populations. In addition, it may spread the seeds of several species of plants through its droppings. Finally, its young and eggs provide food for a few bird and snake species. Please see above sections, especially “Food Habits”, for more detailed references.

Yellow-backed orioles are minor crop pests of bananas. (Wetmore, Pasquier, and Olson, 1984)

Yellow-backed oriole foraging habits aid in the regulation of damaging insect populations, especially caterpillars and cerambycid beetles (Wetmore et al., 1984). (Wetmore, Pasquier, and Olson, 1984)

Because Icterus chrysater is well adapted to a variety of habitats and has a wide population distribution, it is unlikely that the existence of this species is under immediate threat (IUCN, 2009). However, human activities, especially the exotic pet trade, have contributed to the decline of this and related species (Skutch, 1996). (Skutch, 1996)

Yellow-backed orioles are most closely related to Audubon’s orioles (Icterus graduacauda), as determined by Omland et al. through cytrochrome-b and ND-2 gene analysis. The average sequence divergence between the two species is 1.7%. This suggests that, assuming a molecular clock of 2% divergence per million years, the two species diverged less than one million years ago (Omland et al., 1999). (Omland, Lanyon, and Fritz, 1999)