The Baltimore oriole is a small colorful bird that received its name from the resemblance of the male's colors to those on the coat-of-arms of Lord Baltimore. The adult male is orange on the underparts shoulder patch and rump. 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. Adult birds always have white bars on the wings.
Baltimore orioles are found in 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. These birds prefer large, leafy deciduous trees, but do not generally reside in deep forests. They can be found 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, Baltimore orioles winter in flowering canopy trees, often over shade coffee plantations.
Baltimore orioles are generally solitary and interact with their mates only during the breeding season. These birds are active during the day and find their food in trees and shrubs; they also make short flights to catch insects. Orioles acrobatically clamber, hover, and hang among foliage as they comb high branches. Their favored prey is perhaps the forest tent caterpillar moth, which they typically eat in their larval stage. The larvae caterpillar are beaten against a branch until their protective hairs are skinned off before being eaten. 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. Baltimore orioles are vocal birds. Males sing all summer loud flutey whistles, with a buzzy, bold quality, which is a familiar sound in much of the eastern United States. Males typically sing from the tree canopy, often giving away their location before being sighted. Females also sing but heir song is generally shorter and simpler.
Baltimore orioles are considered monogamous forming pairs after courtship displays, although extra-pair copulation is reasonably 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. Breeding usually occurs from May to June. The female is responsible for nest construction. 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. The nest is usually located around 7 to 9 m (23 to 30 ft) above the ground. The female lays 3 to 7 pale gray to bluish-white eggs. 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. They reach reproductive maturity and start to breed in the first year of age. If the eggs, young, or nest are destroyed, the oriole is unable to lay a replacement clutch.
Baltimore orioles are not threatened or endangered but they are vulnerable to habitat loss and deforestation. They are also poisoned by the pesticides that are used to eliminate insects and in some areas, orioles are considered a pest and can be persecuted.
According to the IUCN Red List, the total Baltimore oriole population size is around 6, 000,000 mature individuals. According to the All About Birds resource the total breeding population size of the species is 12 million breeding birds. Overall, currently, Baltimore orioles are classified as least Concern (LC) on the IUCN Red List and their numbers today are stable.
Baltimore orioles play an important role in their ecosystem. These birds protect trees from damage as they feed mainly on insects such as caterpillars which do a lot of harm to plants.