Icterus auratusorange oriole

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Geographic Range

Orange orioles (Icterus auratus) are endemic to the the Yucatan peninsula (Davis 1972; Howell and Webb 1995; Jaramillo and Burke 1999), including the Mexican states Quintana Roo, Campeche, and Yucatan as well as the northern tip of Belize. Considering the narrow range inhabited by this species, it is unsurprising that there does not appear to be any evidence of regional physical or behavioral variation. (Davis, 1972; Howell and Webb, 1995; Jaramillo and Burke, 1999)

Habitat

Orange orioles are a riparian edge species; they tend to live in forested habitat near bodies of flowing fresh water (Jaramillo and Burke 1999; Skutch 1996). Open woodlands and forest edge are preferred habitats but they are also commonly found in scrub forest and savanna, including flooded scrub forest (Howell and Webb 1995). Orange orioles may also be found near cenotes, a type of flooded sinkhole that is common in the Yucatan (Jaramillo and Burke 1999). (Howell and Webb, 1995; Jaramillo and Burke, 1999; Skutch, 1996)

Physical Description

As their name implies, orange orioles are primarily orange and black, although many other oriole species are as orange. The bill is straight and black, fading to blue at the base of the lower mandible. In adult males, the head, upperparts, and underparts are orange, the body being more yellow than the head and nape (Howell and Webb 1995; Jaramillo and Burke 1999). By contrast, the throat patch, lores, and shoulders are black (Howell and Webb 1995; Jaramillo and Burke 1999). Two broad white wing bars are visible against each brownish-black wing; occasionally, only one wing bar is visible, the other having been lost through abrasion. The primary flight feathers are edged in white, forming a characteristic “handkerchief” (Jaramillo and Burke 1999). (Howell and Webb, 1995; Jaramillo and Burke, 1999)

Adult females are similar to adult males but duller. Their upperparts are washed olive. Jaramillo and Burke (1999) report that adult females are also more yellow than their male counterparts. In addition, the wingbars are narrower than in males. The tail is brown instead of black, though the overall pattern is conserved.

Immature males are similar to adult females, but with a brighter, wider wing bar (Jaramillo and Burke 1999). By contrast, the wing bar is absent in immature females. Immature females in particular have greener upperparts than those of adult females (Howell and Webb 1995). Unlike adult members of this species, both immature males and immature females have olive tails.

Juveniles are similar to immature members of the species, though they entirely lack black; the regions that are black in adults are instead dark brown (Jaramillo and Burke 1999). Wing bars, though present, are yellow (Howell and Webb 1995).

Orange orioles molt once yearly in the months following the breeding season (Jaramillo and Burke 1999). (Howell and Webb, 1995; Jaramillo and Burke, 1999)

Several species have plumage resembling that of Icterus auratus; these include hooded orioles (Icterus cucullatus), yellow-backed orioles (Icterus chrysater), and orchard orioles (Icterus spurius). Orange orioles can be distinguished from hooded orioles in the following manner: hooded orioles have a curved bill and lack the wing markings (the “handkerchief”) seen in adult orange orioles. Yellow-backed orioles resemble adult orange orioles but, as their common name implies, are yellow; in addition, yellow-backed orioles are somewhat larger. Orchard orioles have a similar plumage pattern and overall body size, but are much darker; male orchard orioles also lack the handkerchief found in adult male orange orioles (Jaramillo and Burke 1999). (Jaramillo and Burke, 1999)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful

Reproduction

Orange orioles tend to be colonial nesters, a trait unusual for members of the genus Icterus. Orange orioles breed once yearly, in groups of up to 35 nests. It is common to observe multiple nests in a single tree, with a maximum concentration of 5 nests to a tree (Jaramillo and Burke 1999). (Jaramillo and Burke, 1999)

Nests are found between the upper branches of trees and low bushes, and are most often hung less than 10 meters from the ground. Nests are often found in trees overhanging bodies of water, especially sinkholes (cenotes) (Howell and Webb 1995). Orange oriole nests are wide, pendant structures that are shallow relative to the nests of other oriole species (Howell and Webb 1995; Jaramillo and Burke 1999). Nests are usually woven of fine plant fibers in a loose pattern such that light can easily penetrate the weave (Howell, Webb, and DeMontes 1992). They are often easy to spot, considering their unusual construction and conspicuous locations (Jaramillo and Burke 1999). (Howell and Webb, 1995; Howell, et al., 1992; Jaramillo and Burke, 1999)

Due to a lack of information, parental investment in this species could not be determined.

Lifespan/Longevity

Due to insufficient data, the longevity of this species could not be assessed.

Behavior

Little is known regarding orange oriole behavior; however, orange orioles are generally social and have been observed to congregate in small flocks. These flocks not only include conspecifics, but also other oriole species and catbirds. Orange orioles generally forage in what appear to be mated pairs (Davis 1972; Howell and Webb 1995). (Davis, 1972; Howell and Webb, 1995)

Home Range

Due to insufficient information, the home range of this species could not be determined.

Communication and Perception

Orange orioles generally have a melodious whistling voice, a characteristic they share with most of the other Icterus species. Jaramillo and Burke (1999) describe the song as a sweet whistle with notes lasting an average of two seconds. The song frequently changes in pitch, doing so about four times per second. In addition, orange orioles possess a chattering call described by Davis (1972) as “a thin introduction followed by a series of che figures”. (Davis, 1972; Jaramillo and Burke, 1999)

Food Habits

Little is known regarding the diet of orange orioles. However, considering the food habits of other species in the genus Icterus, orange orioles are most likely insectivorous, supplementing their diet with nectar, berries, and occasionally orchard fruit.

  • Animal Foods
  • insects
  • Plant Foods
  • fruit
  • nectar

Predation

Although statistics regarding predation on orange orioles by other species are not available, one can make several speculations based on the incidence of predation and nest parasitism in other Central American oriole species. Likely predators include jays, snakes, and squirrels, all of which feed on the eggs and young of several oriole species. This species is also most likely parasitized by brown-headed cowbirds, which is known to lay eggs in the nests of several other blackbird and oriole species.

Ecosystem Roles

Their role in the Yucatan ecosystem could not be verified from available data; however, they are likely to be responsible for dispersing the seeds of some plants.

Economic Importance for Humans: Positive

Orange orioles have not been extensively studied, with only a handful of peer-reviewed articles in existence that deal with this species. As such, this species and its attendant ecosystems is a candidate for scientific investigation. Because it is a striking species not observed outside the Yucatan, this species may also be of interest to tourists and birdwatchers.

  • Positive Impacts
  • ecotourism
  • research and education

Economic Importance for Humans: Negative

This species does not appear to negatively impact the economy in the regions where it is found.

Conservation Status

According to BirdLife International (2010), the species is listed as “Least Concern” for the following reasons. It is estimated that there are in excess of 20,000 mature individuals occupying more than 100,000 square kilometers of territory. These data do not fall below the thresholds for “Vulnerable” status as indicated by the IUCN. Especially large populations of orange orioles may be found in Belize. (Butchart, et al., 2009)

Other Comments

Orange orioles are most closely related to the clade including Altamira orioles (Icterus gularis) and yellow orioles (Icterus nigrogularis), as determined by Omland et al. (1999). Average genetic divergence between Icterus auratus and both I. gularis and I. nigrogularis is approximately 4%. Assuming an average rate of genetic divergence of about 2% per million years, it is likely that orange orioles split off of the lineage leading to I. gularis and I. nigrogularis about two million years ago. (Omland, et al., 1999; Omland, et al., 1999)

Contributors

Matthew Murphy (author), University of Maryland, Baltimore County, Kevin Omland (editor), University of Maryland, Baltimore County, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

Butchart, S., J. Ekstrom, J. Bird. 2009. "Species Factsheet: Icterus auratus" (On-line). Accessed April 29, 2010 at http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=9684&m=0#.

Davis, L. 1972. A Field Guide to the Birds of Mexico and Central America. Austin, TX: University of Texas Press.

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

Howell, S., S. Webb, B. DeMontes. 1992. Colonial nesting of the orchard oriole. Wilson Bulletin, 104(1): 189-190.

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

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(2): 224-239.

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

Wheatley, N., D. Brewer. 2001. Where to Watch Birds in Central America, Mexico, and the Caribbean. Princeton, NJ: Princeton University Press.