Baltimore orioles eat primarily caterpillars, including many pest species. They also eat other insects, some small fruits, and nectar. They are an important predator of the nuisance forest tent caterpillar, Malacosoma disstria, which it eats in both its larval and pupal forms. Large larvae are seized and smashed against a twig to break them open and avoid the setae (stiff, hair-like structures). Pupae are pulled out of their cocoon.
In suburban and rural areas, I. glabula can be attracted to feeders by providing orange halves, grape jelly, or artificial nectar. Adults who come to feeders will take their young to the feeder once they are fledged.
Baltimore orioles eat primarily caterpillars, including many pest species. They also eat other insects, some small fruits, and nectar. They are an important predator of the nuisance forest tent caterpillar, which it eats in both its larval and pupal forms. Large larvae are seized and smashed against a twig to break them open and avoid the setae (stiff, hair-like structures). Pupae are pulled out of their cocoon.
In suburban and rural areas, Baltimore orioles can be attracted to feeders by providing orange halves, grape jelly, or artificial nectar. Adults who come to feeders will take their young to the feeder once they are fledged.
Animal Foods: insects; terrestrial non-insect arthropods; mollusks
Plant Foods: fruit; nectar
Primary Diet: carnivore (Insectivore )
Baltimore orioles have many different kinds of predators, including larger birds and mammals. Most predators take eggs, nestlings, or fledglings. In western Massachusetts, avain predators caused 16% of egg losses and 9% of nestling and fledgling losses. In response to predators, both males and females give alarm calls, and chase and mob (harass) predators.
Known Predators:
Adult birds are 17 to 20 cm long, somewhat smaller than a robin. There is sexual dimorphism in plumage and in size; males are 1-5% larger than females in a variety of measurements. Adult males have a black head, bill, and back, and a bright orange breast, rump, and underparts. Their wings are black with orange and white wing bars, and the tail is orange with black streaks. Adult females are paler than males, olive-brown to orange. Their wings are brown with white wing bars, and the bill is gray. She may have traces of black on her head. Immature animals are variable, but typically resemble the female. Males take over a year to reach adult plumage.
Range mass: 28 to 42 g.
Range length: 17 to 20 cm.
Range wingspan: 9 to 10 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful
Average basal metabolic rate: 0.5052 W.
The oldest recorded Baltimore oriole in the wild lived to 11 years and 7 months old. They have been recorded living 14 years in captivity.
Range lifespan
Status: wild: 11.5 (high) years.
Range lifespan
Status: captivity: 14 (high) years.
Average lifespan
Status: wild: 139 months.
Baltimore orioles prefer open woods, with a strong preference for deciduous over coniferous trees. They are very adaptable, however, and can be found breeding in a variety of habitats. They are rare on farmlands but have adapted well to urban parks and suburban landscapes. In Mexico, they winter in flowering canopy trees over shade coffee plantations.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest ; rainforest ; scrub forest
Other Habitat Features: urban ; suburban ; agricultural ; riparian
Baltimore orioles are neotropical migrants. They spend summers in the Nearctic, primarily the eastern United States. They breed from Wisconsin to Maine and south to central Mississippi and Alabama, northern Georgia, and western South Carolina and North Carolina. They winter in the neotropics as far north as Mexico and sometimes the southern coast of the United States.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Baltimore orioles are important predators on insects in the communities in which they live. Because they live in forested areas and prey on caterpillars, the lifestage at which many insects do most damage to plants, they are especially important in protecting forest trees from damage.
Baltimore orioles are attractive songbirds that will come to feeders. They are generally liked by both serious birdwatchers and casual backyard enthusiasts for both their appearance and song. They are also important predators on some insect pests such as forest tent caterpillars.
Positive Impacts: ecotourism ; controls pest population
Baltimore orioles may occasionally damage crops of peas or small fruits.
Negative Impacts: crop pest
Baltimore orioles are protected by the Migratory Bird Treaty Act. They may be at risk due to habitat loss, as they prefer wooded areas, but this is not well documented. Although direct human impacts on oriole populations are unknown, the increase in number of orioles wintering in temperate North America may be due to an increase in bird feeders in backyards and elsewhere.
US Migratory Bird Act: protected
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
The male sings all summer. His song is rich and flute-like, with each individual having a distinct song. The female song is generally shorter and simpler. The call, from both sexes, is a whistled "hew-li." Nestlings beg loudly.
Baltimore orioles also use postures and movements to communicate, such as male courtship displays, female wing-flutter displays, and nestling wing-flutters when begging for food.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Baltimore orioles were previously considered a supspecies of northern orioles (Icterus galbula galbula) along with Bullock's orioles (Icterus glabula bullockii), a western North American oriole. They are currently considered separate species: Baltimore orioles, Icterus galbula, and Bullock's orioles, Icterus bullockii. Some hybridization occurs in the Great Plains where these species overlap.
Baltimore orioles are generally considered monogamous, although evidence suggests that extra-pair copulation is reasonably common. In the spring, males display to females on their territory by singing and/or chattering while hopping from perch to perch in front of her. Males give a bow display, bowing with wings lowered and tail fanned. Some females ignore these displays while others sing and give calls or a wing-quiver display in response. The wing-quiver display involves leaning forward, often with tail partly fanned, and fluttering or quivering slightly lowered wings.
Mating System: monogamous ; polygynandrous (promiscuous)
Males arrive on breeding grounds in the spring a few days before females. Courtship displays by the male consist of bowing, to show off the bright orange front and black back, and singing. The female builds a woven pouch nest hanging from the end branches of trees, well concealed by leaves. She builds a new nest each year with little or no help from the male. Icterus galbula prefers to build in elms, maples, willow, or apples, twenty-five to thirty feet above the ground. Any available plant and animal fibers may be used.
The female lays four to six eggs, typically four. The eggs are pale grayish or bluish white, irregularly blotched and streaked with browns and black. The female incubates for twelve to fourteen days. Both parents feed the nestlings. Fledglings will stay with their parents for two weeks, and are fed by their parents duing that period. Baltimore orioles lay only one brood per season.
Breeding interval: Baltimore orioles breed once yearly.
Breeding season: Breeding occurs from May to June.
Range eggs per season: 3 to 7.
Average eggs per season: 4.
Range time to hatching: 11 to 14 days.
Average time to hatching: 12 days.
Average time to independence: 2 weeks.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average eggs per season: 4.
The female alone broods nestlings; the male occasionally feeds the brooding female, but she usually forages for herself. Parents feed nestlings by regurgitation during the first few days of the nesting period.
Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
The Baltimore oriole (Icterus galbula) is a small icterid blackbird common in eastern North America as a migratory breeding bird. It received its name from the resemblance of the male's colors to those on the coat-of-arms of 17th century Lord Baltimore. Observations of interbreeding between the Baltimore oriole and the western Bullock's oriole, Icterus bullockii, led to both being classified as a single species, called the northern oriole, from 1973 to 1995. Research by James Rising, a professor of zoology at the University of Toronto, and others showed that the two birds actually did not interbreed significantly.[2]
The Baltimore oriole is the state bird of Maryland. It is also the namesake and mascot for the Baltimore Orioles baseball team.
The Baltimore oriole was one of the many bird species originally described by Carl Linnaeus in the 1758 10th edition of his Systema Naturae, where it was given the binomial name of Coracias galbula.[3]
Like all New World orioles, this species is named after an unrelated, physically similar family found in the Old World: the Oriolidae. "Oriole" ultimately derives from Latin aureolus, "golden".[4] The genus name Icterus is from Ancient Greek ikteros, a yellow bird, usually taken to be the Eurasian golden oriole, the sight of which was thought to cure jaundice. The specific galbula is the Latin name for a yellow bird, again usually assumed to be the golden oriole.[5]
This medium-sized passerine measures 17–22 cm (6.7–8.7 in) in length and spans 23–32 cm (9.1–12.6 in) across the wings. Their build is typical of icterids, as they have a sturdy body, a longish tail, fairly long legs and a thick, pointed bill. The body weight averages 33.8 g (1.19 oz), with a range of weights from 22.3 to 42 g (0.79 to 1.48 oz).[6] The male oriole is slightly larger than the female, although the size dimorphism is minimal by icterid standards.[7][8][9] Adults always have white bars on the wings.
The adult male is orange on the underparts shoulder patch and rump, with some birds appearing a very deep flaming orange and others appearing yellowish-orange. All of the rest of the male's plumage is black. The adult female is yellow-brown on the upper parts with darker wings, and dull orange-yellow on the breast and belly. The juvenile oriole is similar-looking to the female, with males taking until the fall of their second year to reach adult plumage.
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Baltimore orioles are found in the Nearctic in summer, including the Canadian Prairies and eastern Montana in the northwest eastward through southern Ontario, southern Quebec and New Brunswick and south through the eastern United States to central Mississippi and Alabama and northern Georgia. They migrate to winter in the Neotropics as far north as Mexico and sometimes the southern coast of the United States, but predominantly in Central America and northern South America. Some areas of the southern United States may retain orioles all winter if they have feeders that appeal to them. The range of this bird overlaps with that of the similar Bullock's oriole in the Midwest, and the two species were once considered to be conspecific under the name northern oriole because they form fertile hybrids. The Baltimore oriole is a rare vagrant to Western Europe.
Baltimore orioles are often found high up in large, leafy deciduous trees, but do not generally reside in deep forests. The species has been found in summer and migration in open woodland, forest edge, and partially wooded wetlands or stands of trees along rivers. They are very adaptable and can breed in a variety of secondary habitats. In recent times, they are often found in orchards, farmland, urban parks and suburban landscapes as long as they retain woodlots. In Mexico, they winter in flowering canopy trees, often over shade coffee plantations.[10]
From 1966–2015, the Baltimore oriole experienced a greater than 1.5% annual population decrease throughout the northern and eastern parts of its breeding range.[11] Among other causes Dutch elm disease destroyed a meaningful amount of their favorite nesting locations: elm trees.[12]
The male sings a loud flutey whistle, with a buzzy, bold quality, a familiar sound in much of the eastern United States. The male typically sings from the tree canopy, often giving away its location before being sighted.
Baltimore orioles are basically solitary outside their mating season. The species is generally considered monogamous, although evidence suggests that extra-pair copulation is relatively common. In the spring, males establish a territory then display to females by singing and chattering while hopping from perch to perch in front of them. Males also give a bow display, bowing with wings lowered and tail fanned. Depending on their receptiveness, the females may ignore these displays or sing and give calls or a wing-quiver display in response. The wing-quiver display involves leaning forward, often with tail partly fanned, and fluttering or quivering slightly lowered wings.
The Baltimore oriole's nest is built by the female. It is a tightly woven, bindle-like pouch located on the end of a branch, consisting of any fine plant or animal materials available, hanging down on the underside.[13] Trees such as elm, cottonwood, maple, willow, or apple are regularly selected, with the nest usually located around 7 to 9 m (23 to 30 ft) above the ground. The female lays three to seven eggs, with the norm being around four. The eggs are pale gray to bluish white, measuring 2.3 cm × 1.6 cm (0.91 in × 0.63 in) on average. The incubation period is 12 to 14 days. Once the nestlings hatch, they are fed by regurgitation by both parents and brooded by the female for two weeks. After this the young start to fledge, becoming largely independent shortly thereafter. If the eggs, young, or nest are destroyed, the oriole is unable to lay a replacement clutch.[10]
Predation of adults is a common source of mortality, typically also occurring with eggs, nestlings and fledglings. Common predators at Baltimore oriole nests can include common grackles, American crows, blue jays, black-billed magpies, tree squirrels and domestic cats, which most commonly capture newly fledged orioles or adults engaged in brooding behavior. Rapacious birds commonly prey on both young and fully-grown orioles, the most prolific being the eastern screech owl and Cooper's and sharp-shinned hawks. Somewhat larger rapacious birds also sometimes opportunistically prey on the oriole, including peregrine falcons, great horned owls, and barn owls, while merlins may do so while orioles are migrating.[14][15]
The record lifespan for a wild bird was 12 years and 0 months (based on a banded bird killed by a peregrine falcon), with captive orioles living up to 14 years.
Baltimore orioles forage in trees and shrubs, also making short flights to catch insects. They acrobatically clamber, hover and hang among foliage as they comb high branches. They mainly eat insects, berries and nectar, and are often seen sipping at hummingbird feeders. Their favored prey is perhaps the forest tent caterpillar moth, which they typically eat in their larval stage, and can be a nuisance species if not naturally regulated by predation. The larvae caterpillar are beaten against a branch until their protective hairs are skinned off before being eaten. They will also consume beetles, grasshoppers, wasps, bugs, and spiders.[12] Unlike American robins and many other fruit-eating birds, Baltimore orioles seem to prefer only ripe, dark-colored fruit. Orioles seek out the darkest mulberries, the reddest cherries, and the deepest-purple grapes, and will ignore green grapes and yellow cherries even if they are ripe. Baltimore orioles sometimes use their bills to "gape", stabbing their closed bill into soft fruits, then opening it to lap the juice with their tongues. During spring and fall, nectar, fruit and other sugary foods are readily converted into fat, which supplies energy for migration. Many people now attract Baltimore orioles to their backyards with oriole feeders. Many contain essentially the same food as hummingbird feeders, but are designed for orioles, and are orange instead of red and have larger perches. Baltimore orioles are also fond of halved oranges, grape jelly and, in their winter quarters, the red arils of gumbo-limbo (Bursera simaruba).[16] If they discover a well-kept feeder, orioles lead their young there.
The Baltimore oriole (Icterus galbula) is a small icterid blackbird common in eastern North America as a migratory breeding bird. It received its name from the resemblance of the male's colors to those on the coat-of-arms of 17th century Lord Baltimore. Observations of interbreeding between the Baltimore oriole and the western Bullock's oriole, Icterus bullockii, led to both being classified as a single species, called the northern oriole, from 1973 to 1995. Research by James Rising, a professor of zoology at the University of Toronto, and others showed that the two birds actually did not interbreed significantly.
The Baltimore oriole is the state bird of Maryland. It is also the namesake and mascot for the Baltimore Orioles baseball team.
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