The Bullock’s Oriole is a striking songbird of the American West, instantly recognizable by the male’s brilliant orange and black plumage. As a highly migratory species, it spends its breeding season across western North America, favoring open woodlands and riparian corridors before migrating south to Mexico and Central America for the winter. This omnivorous western oriole has a varied diet that shifts dramatically depending on the season and the bird’s biological needs.
Primary Diet: Invertebrates and Protein Sources
The majority of the Bullock’s Oriole’s diet, especially during the breeding season, consists of insects and other arthropods. Approximately 60% of their diet is composed of animal matter, which provides the high protein necessary for raising nestlings. This insectivorous focus is most pronounced in spring and early summer.
The oriole consumes a wide range of invertebrates, including beetles, weevils, ants, and scale insects. Caterpillars are a significant food source for both adults and chicks. Other common prey items include grasshoppers, crickets, and spiders plucked from foliage or webs. They also exhibit specialized behaviors, such as removing the stinger from honeybees before consumption.
Secondary Diet: Nectar, Fruit, and Sap
While insects are the primary food source during the nesting period, plant-based foods become increasingly important as the summer progresses and during migration, providing quick energy from sugars and carbohydrates. Fruits can account for up to 40% of the adult oriole’s summer diet. They readily consume ripe, dark-colored fruits and berries, such as cherries, mulberries, raspberries, and blackberries.
The bird is also a dedicated nectarivore, frequently visiting flowering plants like agaves and the introduced eucalyptus for sugary sustenance. Orioles will often use their sharp, pointed bills to pierce the base of a flower—a method known as ‘nectar robbing’—to access the sugary liquid without pollinating the plant. They may also utilize holes drilled by sapsuckers to drink tree sap, further supplementing their sugar intake. These high-energy foods are particularly beneficial for fueling the long-distance migration to their wintering grounds in Mexico and Central America.
Specialized Foraging Behavior
The Bullock’s Oriole employs several specialized foraging techniques to acquire its varied diet, utilizing its agility and unique bill structure. The most common method is “gleaning,” where the bird actively picks insects and other arthropods directly off the surfaces of leaves, branches, and trunks. They are often observed hanging upside down from the outer canopy of trees to reach hidden prey on the underside of foliage.
Another distinctive feeding technique is “gaping,” which involves inserting the closed bill into a tough-skinned food item and then prying the mandibles open to create a gap. They use this technique to access the pulp and juices of fruits or to open rolled leaves to extract hidden insects. The bird’s tongue is brushy, which helps it lap up the pooling liquids after gaping. Orioles primarily forage in the canopy and dense shrubs, rarely descending to the ground, focusing their search on trees like cottonwood, willow, and mesquite.
Encouraging Orioles Through Backyard Feeding
For those in the oriole’s western range, attracting these bright birds to a backyard requires catering to their sweet tooth, especially during their spring arrival. Placing feeders out in early spring, just before their expected arrival, can establish the yard as a reliable source of food after their exhausting migration. The color orange is a strong visual cue for the birds, and using orange feeders or placing offerings near orange objects can increase visibility.
The most effective backyard foods are high in sugar, such as oranges cut in half and placed on a spike or dish feeder. Grape jelly is a favorite, though it should be offered in small, accessible dishes and changed frequently to prevent spoilage.
Orioles will also readily drink sugar water from nectar feeders, similar to those used for hummingbirds, but they prefer feeders with perches since they cannot hover effectively. To provide the protein they need, especially during nesting, offering live or dried mealworms in a shallow dish can be highly effective. Planting native fruit-bearing trees and shrubs like black cherry or serviceberry provides natural, long-term forage that supports both the adults and the local insect population they depend on.