Baltimore Oriole

The Baltimore oriole is a migratory songbird of eastern North America, named after the orange heraldic crest of England’s Baltimore family. These brightly colored birds have a solid black head, followed by a blazing orange body and wings stroked with bold white.

They are expert architects, building sock-like hanging nests with grass, wool, and artificial fibers on tall deciduous trees. Being voracious feeders of various caterpillars and pests, they play an indispensable role in maintaining the ecological balance of the predator-prey population in their ecosystem.

Description

Size: Length – Body – 17 to 22 cm (6.7 to 8.7 inches); Wingspan – 23 to 30 cm (9.0 to 11.8 inches)

Weight: 22 to 42 g (0.79 to 1.48 oz)

Body and Coloration:

These medium-sized songbirds have long, thick-based, pointed bills, a characteristic feature of the Icteridae family. 

Adult males have a solid black head and flame-orange breast, rump, and underparts. Their wings are black, streaked with orange and white bars, and the tail is orange with bold black strokes. They require over a year to attain adult plumage, molting into orange feathers only after the fall of the second year. In contrast, females and immature males have olive-brown to orange breasts, gray heads, and white wing bars. 

Distribution

They are found in the Nearctic region during the summer, spread across the Canadian prairies, eastern Montana, southern Ontario, and southern Quebec, extending southwards into the eastern United States to central Mississippi, Alabama, and north Georgia.

During winter, they migrate to the Neotropics, moving farther south of the United States, Mexico, and northern South America.

Habitat

They are often spotted on leafy deciduous trees in open woodlands, forest edges, and trees along the rivers. They can adapt to secondary habitats like backyards, orchards, plantations, urban parks, and suburban landscapes.

Diet

Baltimore orioles feed primarily on a range of caterpillars, like gypsy moth caterpillars, fall webworms, and spiny elm caterpillars. They are an important natural predator of the forest tent caterpillar Malacosoma disstria, consumed in both pupal and larval forms. These migratory birds also feed on insects like beetles, crickets, grasshoppers, moths, spiders, snails, and other small invertebrates.

During spring and fall, their diet is supplemented by sugary fruits and nectar, from which they derive energy for migration. Unlike many other fruit-eating birds, these orioles prefer only ripe and dark-colored fruits. They search for the darkest mulberries and cherries and ignore the green and yellow ones, even if they are ripe. It is easy to attract them with oranges, grape jelly, peanut butter, and even artificial nectar. 

Behavior

• These songbirds have a characteristic singing pattern, including a short set of sweet whistles and high-pitched nasal calls that often sound like ‘tyew li.’ Throughout summer, the males sing a flute-like song that includes a brief sequence of notes that are paired and repeated 2-7 times. The females also vocalize, fiercely screeching while protecting their nests. Both sexes could let out warning calls that often sound like inharmonious chatter when combating each other. 

• They are absolute acrobats, clambering, hovering, and hanging among foliage to explore the higher branches and twigs for food. They also fly out from perches and quickly snatch insects from the air.
• Though usually found feeding in higher branches, they are also spotted in lower heights, plucking fruit from vines, bushes, and hummingbird feeders. Sometimes, they stab their pointed bills into soft fruits (gaping) and open them to lap the juices with brushy-tipped tongues.

Lifespan

These orioles can live as long as 11 years in the wild, while the oldest one recorded was over 12 years old at the time of its death. In captivity, they can survive up to 14 years.

Reproduction and Life Cycle

They are generally monogamous, though extra-pair copulations are relatively common. In central North America, their range overlaps with its close relative, the Bullock’s Oriole, and the two species often interbreed. 

In spring, the males arrive on the breeding grounds before the females and establish a breeding territory to display themselves by singing or chattering and hopping from perch to perch. They present a characteristic ‘bow display,’ bowing with lowered wings and fanning their tails to reveal their bright orange backs. The females may completely ignore these signals or reciprocate by a ‘wing-quiver’ display, leaning forward with the partly-fanned tail and quivering the lowered wings.

After copulation, the female chooses a nesting site within the territory established by her partner. She then gathers materials like grass, grapevine bark, wool, horsehair, and artificial fibers like cellophane or twine for constructing the nest. 

These orioles weave a sock-like hanging nest, 3 to 4 inches deep, with a tiny opening 2 to 3 inches wide. There are three stages in building the nest. At first, the female weaves the outer bowl of flexible fibers for essential support. Next, springy threads are tightly woven into an inner bowl, which maintains the nest’s structure. Finally, she adds an inner lining of downy feathers to cushion the eggs. They usually prefer trees like elm, cottonwood, willow, maple, and apple for hanging the nests about 7 to 9 meters (23 to 30 ft) above the ground level.

The female lays three to seven gray to bluish-white eggs measuring approximately 2.3 cm × 1.6 cm (0.91 inches × 0.63 inches.) Following an incubation period of 12 to 14 days, the nestlings hatch, and both parents feed them through regurgitation. After being nursed by the mother for two weeks, the young begin to fledge and become independent.

Predators

Baltimore orioles are commonly predated upon by American crows, common grackles, blue jays, black-billed magpies, and birds of prey like Cooper’s and sharp-shinned hawks. Larger rapacious birds like great horned owls, peregrine falcons, and merlins also opportunistically feed on their eggs, nestlings, and fledglings. 

Conservation Status

Baltimore orioles belong to the Least Concern (LC) category of the IUCN Red List of Endangered Species. According to their report, their current population is estimated to be around 6,000,000 mature individuals.

Though protected by the Migratory Bird Treaty Act, these birds are vulnerable to increasing deforestation and habitat loss and thus require attention.