|blue: breeding; red: wintering|
The Baltimore Oriole (Icterus galbula) is a small icterid blackbird that commonly occurs in eastern North America as a migratory breeding bird. This bird received its name from the fact that the male's colors resemble those on the coat-of-arms of Lord Baltimore. Like all icterids called "orioles", it is named after an unrelated, physically similar family found in the Old World: the Oriolidae. At one time, this species and the Bullock's Oriole, Icterus bullockii, were considered to be a single species called the Northern Oriole.
This medium-sized passerine measures 17–22 cm (6.7–8.7 in) in length and spans 23–32 cm (9.1–13 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 1.5 oz). The male oriole is slightly larger than the female, although the size dimorphism is minimal by icterid standards. 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.
Distribution and habitat 
These birds are found in the Nearctic in summer, primarily the eastern United States. They breed from Wisconsin to Maine and south 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 are sometimes 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.
The male sings a loud flutey whistle, with a buzzy, bold quality, and a belovedly familiar sound in much of the eastern United States. The male typically sings from the tree canopy and his song often gives away the bird's location before any sighting can be made.
Male Baltimore Oriole singing
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Baltimore Orioles are basically solitary outside of their mating season. This species is generally considered monogamous, although evidence suggests that extra-pair copulation is reasonably common. In the spring, males establish a territory and then display to females on by singing and chattering while hopping from perch to perch in front of her. Males also give a bow display, bowing with wings lowered and tail fanned. Depending on her 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. The nest is a tightly woven pouch located on the end of a branch, consisting of any plant or animal materials available, hanging down on the underside. Trees such as elms, cottonwoods, maples, willow or apple trees are regularly selected for nesting sites, with the nest usually being located around 7 to 9 m (23 to 30 ft) above the ground. The female lays 3 to 7 eggs, with the norm being around 4. The eggs are pale gray to bluish white in color, measuring 2.3 cm × 1.6 cm (0.91 in × 0.63 in) on average. The incubation period is 12 to 14 days. Once they hatch, the nestlings are fed by regurgitation by both parents and brooded by the female for a period of 2 weeks. After the 2 week mark, the young start to fledge and become largely independent shortly thereafter. If the eggs, young or nest are destroyed, this oriole (unlike some other bird species) are not known to be able to lay a replacement clutch.
The record lifespan for a wild bird was 11 years and 7 months, with captivity orioles living up to 14 years of age. Few birds are likely to live nearly this long, however. Free-flying birds may fly into electric wires, cars, radio towers or buildings, all of which commonly kill them. Mortality is generally highest in the early stages of life, with starvation and accidents being a contributing factor. The spraying of insecticides may poison them occasionally and nesting and other habits are sometimes interrupted by clear-cutting. Predation is also a common source of mortality, typically also occurring with eggs, nestlings and fledgings. Common predators at Baltimore Oriole nests can include Common Grackles, American Crows, Blue Jays, Black-billed Magpies, tree squirrels and domestic cats. Raptorial birds are commonly a predator of both young and fully-grown orioles, including Eastern Screech Owls and Cooper's and Sharp-shinned Hawks. In western Massachusetts, avain predators caused 16% of egg losses and 9% of nestling and fledgling losses 
They 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. 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 in an unusual way, called “gaping”: they stab the closed bill into soft fruits, then open their mouths to cut a juicy swath from which they drink 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. Oriole feeders 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). If they discover a well-kept feeder, orioles lead their young to the same feeder.
- BirdLife International (2012). "Icterus galbula". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 16 July 2012.
- CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), ISBN 978-0-8493-4258-5.
- Baltimore Oriole, Life History, All About Birds – Cornell Lab of Ornithology. Allaboutbirds.org. Retrieved on 2012-08-23.
- ADW: Icterus galbula: INFORMATION. Animaldiversity.ummz.umich.edu. Retrieved on 2012-08-23.
- Baltimore Orioles, Baltimore Oriole Pictures, Baltimore Oriole Facts – National Geographic. Animals.nationalgeographic.com. Retrieved on 2012-08-23.
- Rising, J., N. Flood. 1998. Baltimore Oriole: The Birds of North America, No. 384: 1–32.
- Foster, Mercedes S. (2007). "The potential of fruiting trees to enhance converted habitats for migrating birds in southern Mexico". Bird Conservation International 17: 45. doi:10.1017/S0959270906000554.
- Lab of Ornithology- Baltimore Oriole profile
- Hilty, Steven L. (2003): Birds of Venezuela. Christopher Helm, London. ISBN 0-7136-6418-5
- Stiles, F. Gary & Skutch, Alexander Frank (1989): A guide to the birds of Costa Rica. Comistock, Ithaca. ISBN 0-8014-9600-4
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