Geographic Range
Orchard orioles breed in Canada, the United States, and Mexico. Their breeding range
extends north to southeast Saskatchewan, through southwest Manitoba, southern Ontario,
central New York and extreme southern Maine, along the entire east coast of United
States through northern Florida, southwest from the Gulf coast of northern Florida
through southern Texas (but absent from Rio Grande Valley), and into inland central
Mexico to southern Guanajuato. The breeding range extends west to eastern Montana
and Colorado, western Texas, and northwestern Oklahoma.
The winter range of orchard orioles includes both coasts of Mexico, through Central
America, and northern South America. On the Pacific Coast they occur north to central
Sinaloa and south to central Oaxaca, where they also occur inland. On the Gulf Coast
they are found as far north as southern Tamaulipas and south to southern Veracruz,
where they are also found inland. Orchard orioles are present on all of the Yucatan
Peninsula and throughout Central America except the highlands of Guatemala and southern
highlands of Nicaragua. They winter as far south as northern Colombia and northwestern
Venezuela.
Orchard orioles migrate over southern Florida in large numbers, and have (very rarely)
been recorded wintering there as well as southern Louisiana.
- Biogeographic Regions
- nearctic
- neotropical
Habitat
Orchard orioles exhibit a preference for settling near a source of water, such as
a lake or river, and may be found in narrow riparian zones, floodplains, or marshes
(Jaramillo and Burke, 1999). They are rather adaptable to local ecosystems. In the
summer nesting season, for instance, they are found in mesquite brushland in Texas,
orchards in Pennsylvania, and phragmite marshes in Louisiana (Scharf and Kren 1996).
During migrations, they often inhabit forest edges where flowering trees and fruits
are available (Scharf and Kren 1996). While overwintering in their southern ranges,
they are found in the same types of habitats: light woods in Colombia, plantations
in Honduras, and tropical forests in Mexico (Scharf and Kren 1996). Overall they
tend to avoid dense forest, preferring more open woods or edge habitats, and are not
usually found in the dry inland scrub regions of Mexico (Scharf and Kren 1996).
Orchard orioles are not particularly sensitive to human activity, and are found in
suburbs, parks, and agricultural lands throughout their geographic range (Scharf and
Kren 1996).
- Habitat Regions
- temperate
- tropical
- terrestrial
- Terrestrial Biomes
- forest
- Aquatic Biomes
- lakes and ponds
- rivers and streams
- Wetlands
- marsh
- Other Habitat Features
- suburban
- agricultural
- riparian
Physical Description
Orchard orioles are the smallest of the North American orioles, averaging 15 to 18
cm in length, with males marginally larger than females. They have a short, squared-off
tail and small, slender bill. The legs and feet are blue-gray and the eyes are dark
brown for both sexes (Jaramillo and Burke 1999).
Breeding adult males are black on the head, neck, upper breast, nape, back, and scapulars. The rump, upper-tail coverts, and underparts from breast to under-tail coverts are rich chestnut. The wings are primarily black, except for chestnut epaulets and white wing bar and tips. The tail is black with narrow brownish-white tips (Jaramillo and Burke 1999).
Non-breeding adult males look much like breeding males, but olive or pale chestnut-tipped feathers may obscure the black coloration on the upperparts. The feathers on the rump and upper tail-coverts as well as the underparts from the breast to the undertail-coverts may have yellowish tips. Brownish white or gray tips on the tail may be more noticeable than on the breeding male (Jaramillo and Burke 1999).
Second year males are similar to adult females, but have a solid black bib and black between the eye and bill. The degree to which black adult plumage appears in this stage varies considerably between individuals, with some males of this age having more black feathering than others (Scharf and Kren 1996). Despite their lack of adult coloration, these males are sexually mature. Though they can breed, they are often unsuccessful in finding a mate because females generally select males with adult plumage (reviewed in Enstrom, 1993).
Hatch year males are similar to adult breeding females, but with more greenish, yellowish,
or brownish upperparts and brighter yellow underparts (Scharf and Kren 1996). Flecked
black feathering on the throat and between the eye and bill is possible (Jaramillo
and Burke 1999).
Juvenile Orchard Orioles of both sexes are similar in appearance to adult females,
but they are browner above and more yellow below (Scharf and Kren 1996). The wings
are pale brown with dull white edges and two buff-white wing bars (Scharf and Kren
1996). The tail is yellowish olive green (Scharf and Kren 1996). The bill is tinged
pink or orange at the base, fading with age to adult black and blue-gray (Jaramillo
and Burke 1999).
Breeding adult females look much like non-breeding adult females, but have brighter underparts, a more mottled appearance on the upperparts, and a yellow sheen on the underside of the tail. Non-breeding adult females are brownish olive from forehead to uppertail-coverts on upperparts. This coloring is brighter on the forehead, more yellow on the rump and uppertail-coverts, and fades to olive on the flanks (Scharf and Kren 1996). The back is dark olive and the wings are dark gray with two white wing bars and white edging (Jaramillo and Burke 1999, Scharf and Kren 1996). The tail is olive above and yellowish underneath (Jaramillo and Burke 1999).
Second year and hatch year females are similar to adult non-breeding females. The
second year females are browner on the underparts and more uniformly brown (less mottled)
on the upperparts than adult females (Scharf and Kren 1996). The hatch year females
are browner above and brighter yellow below than adults (Scharf and Kren 1996). The
transition between these two plumage patterns is slight, and may not be noticeable
in the field (Jaramillo and Burke 1999).
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes colored or patterned differently
- male more colorful
Reproduction
Both second year and full adult males arrive in breeding ranges at the same time in
mid May. Females arrive either with the males or, in the most northerly parts of
their range, soon after (Jaramillo and Burke 1999). Both females and males use courtship
displays to attract mates, including “bowing” (the head is lowered) “seesawing” (the
head and tail are bobbed alternately), and “begging” (the wings are fluttered and
a high trill is sung). The male also uses a flight display, during which he seesaws
while flying (Scharf and Kren 1996).
- Mating System
- monogamous
After pair formation and copulation, females begin building a hanging cup-shaped nest
(Scharf and Kren 1996). Orchard orioles generally prefer to build their nests in
the fork of small branches in trees without a dense canopy, such as willows, elms,
magnolia, and pecan (Scharf and Kren 1996). The nests are also commonly built in
Spanish moss, and have more rarely been found in phragmites grasses (Dennis 1948).
The nest takes the female about six days to complete and is woven from long strands
of grass lined with animal hair, yarn, thin grass, feathers, or other available soft
materials (though it may not be lined at all) (Scharf and Kren 1996).
About seven days after the female begins building the nest, she lays between two and
seven eggs, depending on geographic area (Clawson 1980). The eggs are light blue,
with irregular purple or brown markings mostly on the larger end of the egg (Jaramillo
and Burke 1999).
The female incubates the eggs for 12-14 days, during which the male feeds her and
may guard the nest (Johnsgard 1979, Foss 1994, Scharf and Kren 1996). Once the eggs
hatch, the downy gray or buff-colored chicks are fed by both parents and fledge after
11-14 days in the nest (Scharf and Kren 1996).
The fledglings remain in densely covered habitat close to the nest until the family
unit disbands after about a week (Sealy 1980). Adult females and fledglings of both
sexes stay in the area and feed mainly on fruits in late July and early August when
the males have begun their fall migration (Scharf and Kren 1996).
Orchard orioles are generally considered single-brooders, raising only one brood of
offspring per season. When unseasonably harsh weather or other catastrophes destroy
eggs early enough in the season, they may re-lay, raising one successful brood later
in the breeding season (Scharf and Kren 1996). However, in 2004 three pairs of orchard
orioles in Maryland were observed raising two successful broods in one season (Omland
and Ligi, unpublished data). The second brood was laid as soon as a week to as late
as a month after the young from the first brood had fledged (Omland and Ligi, unpublished
data). Further research may help clarify the question of how prevalent this behavior
is in orchard oriole populations.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
Both male and female orchard orioles play a role in parental care. Females build
the nest and incubate the eggs. During incubation, males feed the female and protect
the nest. When the chicks hatch, the male and female share the responsibilities of
feeding the young and carrying away feces (Scharf and Kren 1996). After the young
have fledged, the male and female remain to forage with the fledglings for about a
week, after which the male begins the fall migration (Sealy 1980). When males leave,
females and young may stay behind and feed in large flocks (Jaramillo and Burke 1999).
- Parental Investment
- altricial
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- male
-
protecting
- male
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- male
- female
-
protecting
- male
- female
-
provisioning
Lifespan/Longevity
The oldest orchard oriole recorded was recaptured in the wild at 9 years and 7 months
old (Scharf and Kren 1996).
Behavior
Orchard orioles are relatively social both within and outside their species. During
the breeding season, they often nest in loose colonies, warning each other of danger
(Scharf and Kren 1996). They also nest near other species, (up to within a meter
of western kingbirds,
Tyrannus verticalis
) which in some cases may be beneficial by reducing nest parasitism from cowbirds
(
Molothrus ater
) (Scharf and Kren 1996). During the winter, they may roost in large numbers (sometimes
more than 100), both with other orchard orioles and other species, including Baltimore
orioles (
Icterus galbula
) and many species of finch (
Fringillidae
)(Bent 1965).
Orchard orioles are diurnal except during spring and fall migrations. They generally
begin foraging at dawn, decrease activity around noon, and are inactive during the
afternoon and evening. When weather interrupts foraging, however, it is resumed later
in the day (Scharf and Kren 1996). During migration, they are nocturnal (Bent 1965).
Orchard orioles migrate in the spring and fall. They leave their wintering grounds
(Central Mexico to Northern Colombia) March through April, and arrive in their breeding
ranges (Eastern United States and Northern Mexico) late April through late May (Scharf
and Kren 1996). They begin leaving the breeding ranges after the young have fledged
in late July to early August, and arrive in wintering grounds around mid-August (Scharf
and Kren 1996).
Home Range
Orchard orioles have been observed nesting semi-colonially with conspecifics, as well
as in close proximity to other species, such as Baltimore orioles (
Icterus galbula
) and Bullock’s orioles (
Icterus bullockii
) (Scharf and Kren 1996). Orchard orioles are not fiercely territorial year-round,
but during the breeding season adult males will defend nesting and foraging areas
from second year males (Scharf and Kren 1996).
Communication and Perception
Females and young orchard orioles communicate vocally through short monotonal whistles
(Scharf and Kren 1996). These vocalizations are especially common during mid-July
to mid-August, after adult males leave the nesting grounds and before the females
and young begin their fall migration (Scharf and Kren 1996).
Adult (including second-year) males sing upon reaching the breeding grounds, most
likely in order to attract a mate, but perhaps to a limited degree to establish foraging
and nesting areas (Scharf and Kren 1996). This song, a high-pitched series of notes
that may include harsh interjections and downward slurs, is similar to that of Baltimore
orioles (
Icterus galbula
) (Scharf and Kren 1996). A soft chuck and chatter may also be used (Scharf and Kren
1996).
Alarm calls comprised of chucks and chatters are used by orchard orioles to warn others
of potential danger (Scharf and Kren 1996). Orchard orioles respond to these warning
calls from their own species as well as similar calls from other species, such as
Baltimore orioles (
Icterus galbula
) or Bullock’s orioles (
Icterus bullockii
) (Clawson 1980, Scharf and Kren 1996). Orchard orioles also use visual signals to
attract mates (see Reproduction).
Food Habits
During the breeding season (late April or early May to mid July), orchard orioles
are mostly insectivorous, but also consume small, ripe fruits and berries, nectar,
and small seeds (Thomas 1946, Dennis 1948, Bent 1965). Stomach content data from
Maryland suggests that their diet consists of about 91% insects and 9% plant material
during this season (Bent 1965).
During their fall migration to southern wintering ranges (arriving as early as the
beginning of July in Mexico) their diet incorporates more ripe fruits and berries
such as mulberries and chokecherries, as well as nectar from roadside flowering trees
and hedges in Mexico (Howell and Webb 1995).
In winter ranges (early or mid July to January), they consume the nectar of tropical
flowering trees and vines such as
Erythrina fusca
, fruits such as mistletoe
Arceuthobium
), and insects obtained from foliage (Scharf and Kren 1996).
During spring migration, an abundance of blooming plants makes nectar a significant
food source along with insects (Scharf and Kren 1996). Orchard orioles passing through
Florida consume blooming black locust (
Robinia pseudoacacia
) nectar in large numbers (Bent 1965), and those in California have been observed
frequently feeding at hummingbird feeders (Small 1994).
- Primary Diet
- omnivore
- Animal Foods
- insects
- terrestrial non-insect arthropods
- Plant Foods
- fruit
- nectar
- flowers
Predation
Common grackles (
Quiscalus quiscula
) in western Nebraska expel young chicks from orchard oriole nests and break unhatched
eggs (Scharf and Kren 1996). Nest parasitism by bronzed cowbirds (
Molothrus aeneus
) and brown-headed cowbirds (
Molothrus ater
) is fairly common, with parasitism rates being recorded as high as 28% (Jaramillo
and Burke 1999). In California, greater roadrunners (
Geococcyx californianus
) have been observed preying on orchard orioles (Binford 1971).
Ecosystem Roles
Orchard orioles are omnivorous, consuming insects and spiders, fruits, nuts, and nectar.
They may help stabilize insect populations through predation in their communities.
Fruits consumed by orchard orioles pass quickly through the bird’s digestive system.
The seeds contained by the fruit remain undigested, spreading the seeds to other areas
through its defecation.
Though they consume nectar, they are not always pollinators of the species they feed
on (Scharf and Kren 1996). For some species, such as the flowering trumpet creeper
(
Campsis radicans
), the bird pierces the flower at the base to obtain the nectar, avoiding the stamens
of the flower and not pollinating the plant (Bent 1965). For other species, such
as
Erythrina fusca
, orchard orioles do serve as a main pollinator (Morton 1979).
Like many other bird species, orchard orioles are hosts for several types of parasites, including blood parasites and various mites (Scharf and Kren 1996). Nest parasitism by bronzed cowbirds ( Molothrus aeneus ) and brown-headed cowbirds ( Molothrus ater ) is fairly common, with parasitism rates being recorded as high as 28% (Jaramillo and Burke 1999).
- Ecosystem Impact
- disperses seeds
- pollinates
- blood parasites ( Hematozoa )
- fowl mites ( Acarina )
- brown-headed cowbirds ( Molothrus ater )
- bronzed cowbirds ( Molothrus aeneus )
Economic Importance for Humans: Positive
Orchard orioles prey upon the cotton boll weevil (
Anthonomus grandis
), a major crop pest for cotton farmers (Oberholser 1974). They are also predators
of many other important agricultural pest species, including caterpillars, plant lice,
beetles, and worms, making them quite beneficial to farmers (Bent 1965).
- Positive Impacts
- controls pest population
Economic Importance for Humans: Negative
Orchard orioles may cause some minor crop damage when nesting on plantations. They
may consume small amounts of stamens from fruit trees, small cultivated berries and
fruits (strawberries, raspberries, cherries), figs, and grapes (Bent 1965)
- Negative Impacts
- crop pest
Conservation Status
Because of population declines since 1982, the American Birds Blue List considers
orchard orioles a species of special concern (Scharf and Kren 1996). Overall, the
eastern population is steady, but the central population has declined in recent years
(Scharf and Kren 1996).
The main cause of population decline is thought to be loss or degradation of habitat.
Destruction of riparian zones and other preferred areas might account for some of
the population’s decline in the central range (Scharf and Kren, 1996). Pesticide
spraying in orchards is another potential issue and has displaced birds in Texas and
Pennsylvania (Oberholser, 1974; Scharf and Kren, 1996).
Orchard orioles are protected by the Migratory Bird Treaty Act of 1918, which prohibits
hunting, trading, and disturbing the nests or eggs of orchard orioles (USFWS, 2002).
Other Comments
Orchard orioles are considered a species complex consisting of two groups, orchard
orioles (
I.s. spurius
) and Fuertes’s or ochre orioles (
I.s. fuertesi
). A third subspecies is also often considered,
I. s. phillipsi
. The classification of these groups is a subject of recent debate. There is uncertainty
as to whether Fuertes’s orioles should remain classified as a subspecies of
Icterus spurius
, as they are now, or considered a separate species, as they were in the past (
I. fuertesi
) (Jaramillo and Burke, 1999). The plumage pattern of Fuertes’s orioles is basically
identical to that of orchard orioles; females and young males of the two groups are
virtually indistinguishable. However, unlike adult male orchard oriole chestnut coloring,
adult male Fuertes oriole’s plumage is described as “ochre” or tan. There appears
to be no color overlap between the groups (Tracy, Hofmann, Cronin, and Omland, unpublished
data).
Recent research into the genetics of Fuertes’s and orchard orioles has suggested that
they are genetically distinct enough to be considered two separate species. By analyzing
similarities in the mitochondrial gene, cytochrome-b, Baker et al. (2003) developed
a phylogenetic tree that shows how closely related different orchard and Fuertes’s
oriole individuals are. The tree that resulted shows that nearly all Fuertes’s orioles
tested were more closely related to each other than to any orchard orioles (Baker
et al., 2003).
Several other factors may support the separation of orchard and Fuertes’s orioles into different species. Perhaps the most immediately obvious difference between the two groups is the difference in adult male coloration. Indeed, this may be a significant difference. Hofmann, McGraw, Cronin, and Omland (unpublished data) used spectral measurements (plumage reflectance) and biochemical analysis to determine which pigments are responsible for the bright colors of orchard and Fuertes’s orioles. The color difference is due to a difference in the relative concentration of melanin and carotenoid type pigments in the feathers of each species. The chestnut color of orchard orioles is predominantly produced by a melanin-based pigment, specifically phaeomelanins; carotenoids are present, but are masked by the melanin (Hofmann, McGraw, Cronin, and Omland, unpublished data). Adult male Fuerte’s orioles have a much lower concentration of phaeomelanins (although it is still a higher concentration than is found in females). In Fuertes’s orioles, phaeomelanins do not completely mask the carotenoid color as they do in orchard orioles; carotenoids and melanins both contribute (Hofmann, McGraw, Cronin, and Omland, unpublished data).
Other differences between orchard and Fuertes’s orioles are their geographic ranges
and migratory habits. Orchard orioles migrate long distances from their breeding
grounds in the United States and Canada to wintering ranges as far south as Colombia,
while Fuertes’s orioles inhabit only a small range, breeding on the eastern coast
of Mexico from southern Tamaulipas to southern Veracruz, and wintering on the Pacific
coast of Mexico from Guerrero to Chiapas (Jaramillo and Burke 1999).
The genus
Icterus
contains 25 recognized species, many of which exhibit very similar plumage patterns
despite being distantly related (Omland and Lanyon 2000). Orchard orioles are an
excellent example of this phenomenon, called “convergence.” Orchard orioles have
a distinct pattern that includes a black head, colored epaulets, and white wing bars.
A nearly identical pattern is found in Baltimore orioles (
I. galbula
), which are distantly related to orchard orioles. Omland and Lanyon (2000) examined
44 specific feather patches to assess the similarity of patterns in different species
of orioles (a process called scoring) and, upon comparing orchard and Baltimore orioles
found that only four of the feather patches between the two species differed in pattern
(2000). These instances of marked similarity between distantly related species occur
repeatedly in
Icterus
.
Additional Links
Contributors
Lynna Kiere (author), University of Maryland, Baltimore County, Kevin Omland (instructor), University of Maryland, Baltimore County.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- 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.
- 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.
- monogamous
-
Having one mate at a time.
- 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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- altricial
-
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- diurnal
-
- active during the day, 2. lasting for one day.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- social
-
associates with others of its species; forms social groups.
- 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.
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
References
Baker, J., E. Lopez-Medrano, A. Navarro-Seguenza, O. Rojas-Soto, K. Omland. 2003. Recent Speciation in the Orchard Oriole group: divergence of Icterus spurius spurius and Icterus spurius fuertesi. The Auk , 120(3): 848-859.
Bent, A. 1965. Life Histories of North American blackbirds, orioles, tanagers, and allies . New York: Dover Publications.
Binford, L. 1971. Roadrunner captures Orchard Oriole in California. California Birds , 2: 139.
Clawson, S. 1980. Comparative ecology of the Northern Oriole (Icterus galbula) and the Orchard Oriole (Icterus spurius) in Western Nebraska . Master's Thesis, University of Nebraska: Lincoln.
Dennis, J. 1948. Observations on the Orchard Oriole in the lower Mississippi Delta. Bird Banding , 19: 12-21.
Enstrom, D. 1993. Female choice for age-specific plumage in the Orchard Oriole: implications for delayed plumage maturation. Animal Behavior , 45: 435-442.
Foss, C. 1994. Atlas of breeding birds in New Hampshire . Arcadia: Audubon Society of New Hampshire.
Howell, S., S. Webb. 1995. A guide to the birds of Mexico and northern Central America . New York: Oxford Univ. Press.
Jaramillo, A., P. Burke. 1999. New World Blackbirds: The Icterids . Princeton: Princeton University Press.
Johnsgard, P. 1979. Birds of the great plains: breeding species and their distribution . Lincoln: Univ. of Nebraska Press.
Morton, E. 1979. Effective pollination of Erythrina fusca by the Orchard Oriole (Icterus spurius):coevolved behavioral manipulation. Ann. Mo. Bot. Gard. , 66: 482-489.
Oberholser, H. 1974. The bird life of Texas Vol. 1 . Austin: Univ. of Texas Press.
Omland, K., S. Lanyon. 2000. Reconstructing plumage evolution in Orioles (Icterus): repeated onvergence and reversal in patterns. Evolution , 54: 2119-2133.
Scharf, W., J. Kren. 1996. Orchard Oriole. Birds of North America , 255: 1-23.
Sealy, S. 1980. Breeding biology of Orchard Orioles in a new population in Manitoba. Can. Field-Nat , 94: 154-158.
Small, A. 1994. California birds: their status and distribution . Vista, CA: Ibis Publ. Co.
Thomas, R. 1946. An Orchard Oriole colony in Arkansas. Bird Banding , 17: 161-167.
2002. "USFWS Division of Migratory Bird Management" (On-line). Birds protected by the Migratory Bird Treaty Act. Accessed April 19, 2005 at http://migratorybirds.fws.gov/intrnltr/mbta/mbtandx.html#alpha1 .