Icterus abeillei
black-backed oriole
(Also: black-backed or abeille's oriole)

Icterus abeillei is endemic to Mexico, and is typically found in central Mexico. Black-backed orioles breed from Durango, Zacatecas and southern Nuevo Leon in the north to Michoacan and Veracruz to the south (Jaramillo and Burke, 1999). They winter to the south of the breeding range, from the central volcanic belt (Michoacan to Puebla and west-central Veracruz) to Oaxaca. (Howell and Webb, 1995; Jaramillo and Burke, 1999)

Black-backed orioles live in dry to semi-humid wooded areas, pine-oak forests, parks, orchards, and wooded riverbanks (Howell and Webb, 1995). They winter in various habitats including mountainous forests in the northern temperate Oyamel Fir zone, pine oak forests in the highlands, wooded riverbanks, urban areas, and other semi-open wooded areas (Jaramillo and Burke, 1999). (Howell and Webb, 1995; Jaramillo and Burke, 1999)

Black-backed orioles are average sized birds that match Bullock’s orioles fairly closely in appearance, especially females and juvenile birds. Adult male black-backed orioles have a black head with an orange, horizontal line in the space between the top of the eye and base of the bill. The bill itself is black with a pale grey lower mandible and the eye has an orange color on the lower crescent giving it a spectacled appearance. The black plumage of male black-backed orioles extends from the crown, over the nape, back, rump, and top tail feathers. The rest of the tail is black and yellow. There is a broad orange cheek area, and a black bib on the throat. The underparts are mostly orange, with an exaggerated orange area on the breast and a yellowish belly and yellow feathers under the tail. There are white markings on the black wings and the legs and feet are a blue-grayish color. (Howell and Webb, 1995; Jaramillo and Burke, 1999)

Female black-backed orioles are more subtley colored than males, but with a similar pattern. They have an olive-grey crown, yellow cheek and forehead. On the midline of the throat there is a pale, whitish stripe. They have a yellow-orange breast and throat that gradually blends into the grayish, pale yellow belly. The back, shoulders, and rump are olive-grey and the uppertail coverts are a light olive yellow. The wings have a blackish brown color with white markings. (Howell and Webb, 1995; Jaramillo and Burke, 1999)

Juveniles look similar to females, except that they are somewhat duller in color, and the plumage is more loosely textured. The underparts are yellow with a subtle green wash.

Male measurements on average are 104.4 mm wing, 85.3 mm tail, 18.1 mm culmen, and 23.7 mm tarsus. Females on average have a 93.9 mm wing, 82.4 mm tail, 18.3 mm culmen, and 23.7 mm tarsus. (Howell and Webb, 1995; Jaramillo and Burke, 1999)

There is little information on the average lifespan of I. abeillei individuals. See the entry for I. galbula.

Black-backed orioles are commonly found in pairs, especially during the breeding season. Outside of the breeding season they are often seen with multiple companions, usually in small flocks, or larger flocks during migration (Jaramillo and Burke, 1999; Howell and Webb, 1995). Their general behavior patterns resemble those of Baltimore orioles (Omland, K.E. personal observation).

Home Range

There is no information regarding the home range of black-backed orioles.

The song and chatter of I. abeillei is considered similar to Bullock’s orioles in a general sense (Jaramillo and Burke, 1999). However, it also only differs from that of Baltimore orioles by 7 vocalization characters (Price, Friedman & Omland 2007). The warble of black-backed orioles is rich and varied, and preceded by gruff, scratchy notes (Howell and Webb, 1995). (Howell and Webb, 1995; Jaramillo and Burke, 1999; Price, Friedman, and Omland, 2007)

A majority of the black-backed oriole diet is composed of insect prey. They also casually feed on nectar. Black-backed orioles are one of two frequent consumers of the toxic monarch butterfly (Danaus plexippus), as they spend their winter together. They eat the inner, less poisonous abdomen of these insects, although they also typically vomit shortly after ingestion. These orioles have been observed eating monarchs over the course of four to seven days, and it is hypothesized that the cycle correlates with their physiological tolerance for the toxins (Arellano et al., 1993 as cited in Jaramillo and Burke, 1999). (Jaramillo and Burke, 1999)

The most likely natural predators of adult I. abeillei are larger birds, such as falcons. Snakes and arboreal mammals prey on eggs and hatchlings in nests. They are likely to have similar predators to those reported for Icterus galbula. Orioles build hanging nests in inaccessible areas, helping to protect their young from predation in the nest.

Black-backed orioles are important predators of insects in the ecosystems they inhabit.

Black-backed orioles are sometimes minor consumers of fruit crops, such as mangoes and berries, as is typical of other orioles.

Black-backed orioles are endemic to central Mexico and have the potential to attract bird watchers and researchers from other parts of the world. Like other orioles, they feed on the nectar of some flowers making them potential pollinators. Black-backed orioles eat insect pests that bother humans and harm crops.

Despite the fact that population size and decline rate analyses have not been undertaken in black-backed orioles, the International Union for the Conservation of Nature and Natural Resources has recognized I. abeillei as a “lower risk/least concern” species. The fact that this oriole species has a fairly restricted range, being endemic to several states in central Mexico, may warrant some degree of monitoring.

Bullock’s and black-backed orioles have similar morphology, several similar behaviors, and are even thought to hybridize. These facts led scientists to believe the two species were close relatives, even including black-backed orioles as a subspecies of Bullock’s orioles (Miller, 1906 as cited in Omland, Lanyon, & Fritz, 1999; Howell and Webb 1995). (Howell and Webb, 1995; Omland, Lanyon, and Fritz, 1999)

Phylogenetic analysis of mitochondrial genetics in the genus Icterus have revealed a close relationship between I. abeillei and Baltimore orioles (I. galbula) (Omland et al., 1999; Kondo, Baker & Omland, 2004). Mitochondrial DNA analysis of divergence between many closely related songbird species indicates that they diverged anywhere from 1 to 4 million years ago (Dunn, 2005). Divergence between I. abeillei and I. galbula, however, shows an average divergence of only 0.26% (Kondo et al., 2004). This correlates with an estimated separation of the two species occurring about 150,000 to 200,000 years ago (Dunn, 2005). Also in their study of this recent speciation between black-backed and Baltimore orioles, Kondo et al. (2004) found that the maximum genetic divergence between individuals within I. galbula is more than the average difference between the two species. (Kondo, 2006; Kondo, Baker, and Omland, 2004; Omland, Lanyon, and Fritz, 1999)

In her 2006 thesis, Kondo addressed relationships within Icterus using nuclear intron DNA. Unlike mitochondrial DNA, which only yields information on maternal patterns of descent, nuclear introns are present in both sexes, yielding information on biparental patterns of descent. Introns also do not accumulate mutations as fast as mitochondrial DNA, providing a different level of resolution for phylogenetic analyses (Moore, 1995 as cited in Kondo et al., 2004). Kondo’s results are congruent with those from mitochondrial DNA analyses, Baltimore and black-backed orioles are recently diverged species. (Kondo, 2006; Kondo, Baker, and Omland, 2004)

Knowing how recently two species diverged is the way taxonomists understand their evolutionary proximity. The fact that Baltimore and black-backed orioles diverged so recently compared to other species of birds, means that they have only been evolving separately for a short period of time. In this short time, however, Black-backed oriole plumage has become different from that of Baltimore orioles in 17 plumage characters, a value that generally corresponds with equally vast differences in mtDNA between species of Icterus (Omland and Lanyon 2000). There is also a clear difference in migratory distance; Baltimore orioles are long distance migrants whereas black-backed orioles are short distance migrants within Mexico (Jaramillo and Burke, 1999; Kondo et al., 2004). While all of this evidence helps us understand the magnitude of the divergence between the species, it leaves other questions to be answered: how did the two species accumulate the differences between them in this time, and how did speciation occur? (Kondo, Baker, and Omland, 2004; Omland and Lanyon, 2000)

Kondo et al. (2004) suggested that black-backed and/or Baltimore orioles experienced a bottleneck during or after their divergence. Nuclear intron data suggests that more than 99.9% of genetic variation in an ancestral population contributes to current genetic variation in Baltimore orioles. This suggests that black-backed orioles were started through a founder event and later grew in size by approximately 50,000 fold (Kondo, 2006). The significance of starting a new population is that the founding black-backed oriole population had a heavy influence early on from random mutations and genetic drift (Kondo, 2006). To this day there are no known cases of hybridization between the two species, although they clearly share a recent common ancestor (Kondo, 2004). Despite the morphological and behavioral differences that have arisen in the short period since their divergence, black-backed and Baltimore orioles share a high percentage of genetic characteristics. (Kondo, 2006; Kondo, Baker, and Omland, 2004)