Icterus chrysater

Geographic Range

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).

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).

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).

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

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).

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).

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• scrub forest scrub forest
• mountains mountains

• Other Habitat Features
• agricultural agricultural

Physical Description

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).

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.

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).

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).

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently

Reproduction

Yellow-backed orioles are socially monogamous.

The nesting season begins in February and lasts through May in northern populations (Jaramillo and Burke, 1999). In contrast, nesting behavior begins in January and continues until October in South American populations (Jaramillo and Burke, 1999). Like most other New World oriole species, individuals of I. chrysater normally attempt to raise one clutch of 2 to 3 eggs per breeding season (Skutch, 1996; Jaramillo and Burke, 1999; but see Ligi and Omland 2007).

The nests of this species take the form of shallow, dangling baskets (Jaramillo and Burke, 1999). They are built so that they hang from the end of a branch, usually a palm frond (Jaramillo and Burke, 1999). Nests are placed high in mature trees, approximately seven meters from the ground (Wetmore et al., 1984). The nests are constructed of plant material, primarily grasses, and have a wiry, springy texture (Wetmore et al., 1984).

Yellow-backed oriole eggs are typical of the genus Icterus : they are whitish, have purple blotches clustered near the wide end of the egg, and are marked with evenly distributed dark brown lines (Jaramillo and Burke, 1999; Wetmore et al., 1984).

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

There is little information available regarding the parental investment of yellow-backed orioles toward their young. However, see the sources at the end of the account for more information.

Lifespan/Longevity

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

Behavior

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 ), Cissilopha jays and orioles of similar size ( Icterus ) (Jaramillo and Burke, 1999; Howell and Webb, 1995).

• Key Behaviors
• arboreal arboreal
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• sedentary sedentary
• social social

Home Range

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

Communication and Perception

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).

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)

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).

• Communication Channels
• visual visual
• acoustic acoustic

• Other Communication Modes
• duets duets

• Perception Channels
• visual visual
• ultraviolet
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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).

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 .

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects
• terrestrial non-insect arthropods

• Plant Foods
• seeds, grains, and nuts
• fruit
• nectar

Predation

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 .

Ecosystem Roles

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.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

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

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

Yellow-backed orioles are minor crop pests of bananas.

• Negative Impacts
• crop pest

Conservation Status

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).

Other Comments

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).

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Matthew Murphy (author), University of Maryland, Baltimore County, Kevin Omland (editor, instructor), University of Maryland, Baltimore County.

References

American Ornithologists’ Union, 1998. Check-list of North American Birds. 7th edition . Washington, DC: American Ornithologists’ Union.

Hofmann, C., T. Cronin, K. Omland. 2008. Evolution of sexual dichromatism. 2. Carotenoids and melanins contribute to sexual dichromatism in New World orioles (Icterus ssp.). The Auk , 125:4: 790-795.

Howell, S., S. Webb. 1995. A Guide to the Birds of Mexico and Northern Central America . New York: Oxford University Press, Inc..

Jaramillo, A., P. Burke. 1999. New World Blackbirds: the Icterids . Princeton, NJ: Princeton University Press.

Leck, C. 1972. Seasonal changes in feeding pressures of fruit- and nectar-eating birds in Panama. Condor , 74: 54-60.

Ligi, S., K. Omland. 2007. Contrasting breeding strategies of two sympatric orioles: first documentation of double brooding by Orchard Orioles. Journal of Field Ornithology , 78:3: 298-302.

Morton, E. 1979. Effective pollination of Erythrina fusca by the orchard oriole (Icterus spurius): coevolved behavioral manipulation?. Annals of the Missouri Botanical Garden , 66:3: 482-489.

Omland, K., S. Lanyon, S. Fritz. 1999. A molecular phylogeny of the New World orioles (Icterus): the importance of dense taxon sampling. Molecular Phylogenetics and Evolution , 12: 224-239.

Price, J., N. Friedman, K. Omland. 2007. .Song and plumage evolution in the New World orioles (Icterus) show similar lability and convergence in patterns. Evolution , 61: 850-863..

Price, J., S. Lanyon, K. Omland. 2009. Losses of female song with changes from tropical to temperate breeding in the New World blackbirds. Proceedings of the Royal Society of London, Series B , 276: 1-10.

Ridgely, B., G. Tudor. 1989. The Birds of South America. Volume 1: The Oscine Passerines . Austin, TX: University of Texas Press.

Skutch, A. 1996. Orioles, Blackbirds, & Their Kin: A Natural History . Tuscon, AZ: The University of Arizona Press.

Wetmore, A., R. Pasquier, S. Olson. 1984. The Birds of the Republic of Panamá. Part 4: Passeriformes: Hirundinidae (Swallows) to Fringillidae (Finches). . Washington, DC: Smithsonian Institution Press.