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).
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 ; acoustic
Other Communication Modes: duets
Perception Channels: visual ; ultraviolet; tactile ; acoustic ; chemical
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).
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Yellow-backed orioles are minor crop pests of bananas.
Negative Impacts: crop pest
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
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
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.
Animal Foods: insects; terrestrial non-insect arthropods
Plant Foods: seeds, grains, and nuts; fruit; nectar
Primary Diet: carnivore (Insectivore )
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 (Native )
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).
Range elevation: 0 to 2900 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest ; scrub forest ; mountains
Other Habitat Features: agricultural
The longevity of this species could not be determined from available information.
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).
Range length: 20.5 to 24 cm.
Average length: 21.5 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes colored or patterned differently
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.
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).
Breeding interval: Yellow-backed orioles breed once or twice yearly.
Breeding season: This species breeds from January until October.
Range eggs per season: 2 to 3.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; 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.
The yellow-backed oriole (Icterus chrysater) is a species of bird in the family Icteridae.
Yellow-backed orioles are a yellow-bodied, sexually monomorphic species. They average 21.5 cm (8.5 in) in length from beak to tail; making it a relatively medium-sized oriole species.[2] Exposed skin and claws are bluish-black; in adults, the bill is black, with the base of the mandible becoming bluish-grey.
Adult males display strongly contrasting yellow and black plumage. The wings, tail, shoulders, throat, and face are all black; by contrast, the back and underparts are an extremely bright yellow. Adult females closely resemble males, but yellow parts appear slightly greenish. Despite differences in plumage coloration between sexes, it is likely that this species is extremely difficult to sex in the field.
Immature yellow-backed orioles resemble adult females in overall pattern, but are greener; additionally, the flight feathers, which are black in females, are dark brown. Immature yellow-backed orioles are easily distinguished from adult females by their olive eye-line.
Similar species include the South American yellow oriole (Icterus nigrogularis).
Yellow-backed orioles are found throughout Central America and northern South America. In particular, the species is divided into three allopatric populations. One population, designated as the subspecies I. c. giraudii, is endemic to southern Central America, including Nicaragua, Panama, and Colombia. The northernmost populations comprise the subspecies I. c. chrysater and I. c. mayanensis; these subspecies are found in northern Central America and in southern Mexico. The species is found in Belize, Colombia, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, and Venezuela.
Yellow-backed orioles are able to tolerate a wide variety of habitats, but prefer open, mixed pine-oak woodlands and dry scrub forest. This species has also been sighted in banana plantations. It has occasionally colonized lowland deciduous forest.
This species is usually found in regions that are less than 900 m (3,000 ft) in altitude, though in Central and South America populations are often seen residing at elevations greater than 1,000 m (3,300 ft). The upper altitude limit for populations observed in the wild appears to be about 3,000 m (9,800 ft).
Yellow-backed orioles are monogamous; like many species of the genus Icterus, they breed once a year with a single mate.
The nests of this species are shallow, dangling baskets that are usually hung from the edge of a tree limb. Members of this species appear to prefer to attach nests to the tips of palm fronds.[3] Nests are usually woven of fine grasses, giving them a springy texture (Wetmore et al. 1984). Nests of this species are normally hung in the canopy of mature trees that are at least 7 m (23 ft) in height.
The eggs of this species are whitish, with purple scrawlings that are concentrated near the broad end of the egg. The eggs are commonly marked with evenly distributed brown lines.[3][4]
Yellow-backed orioles have been observed to congregate in small flocks of up to eight individuals;[4] these flocks are probably family units, as they are composed of individuals at varying stages of maturity. This species occasionally joins mixed-species flocks that include band-backed wrens, jays, and other medium-sized orioles.[3][4]
This species has a clear, whistling voice, with a song resembling that of Spot-breasted orioles (Icterus pectoralis). The song generally consists of a series of clear notes, but it acquires a muddy, warbled quality among populations native to southern Central America.[3][5] Both sexes are known to sing, which appears to be common to orioles that breed in tropical climates.[6] Vocalizations are generally delivered from perches high in trees.[7]
The most commonly used call has been described as a “nasal ‘chert’”,[3] but other calls include a “whistling chatter” and a “nasal alarm”.
Yellow-backed orioles are insectivorous. Their diet consists primarily of caterpillars, wasps, ants, weevils, and other arthropods. This species' diet is often augmented with bananas and may also include nectar from balsa and Heliconia.[8]
This species is often observed foraging in family units or in pairs.[3] Insects are hunted by probing the bark of trees or the leaves of epiphytes. While foraging for nectar, this species sometimes practices "nectar robbing", puncturing the base of an unopened flower to gain access to nectar.[9]
