Bullock's Oriole
Encyclopedia
The Bullock's Oriole, is a small New World blackbird
. At one time, this species and the Baltimore Oriole
were considered to be a single species, the Northern Oriole. This bird was named after William Bullock, an English
amateur naturalist
.
, with males being more brightly colored than females. In addition, adult males tend to be slightly larger and heavier than females. In general, adults range in mass from 29 to 43 grams. Adults have a pointed bill with a straight culmen. In adult males, the tail is long, square, and jet black. All exposed skin is black, as are the claws and bill, though the base of the lower mandible
lightens to bluish-gray.
Adult males are characterized by strongly contrasting orange and black plumage, a black throat patch and a white wing bar. The underparts, breast, and face are orange or yellow; by contrast, the back, wings, and tail are black. A black line extends from each eye to the black crown. The wing coverts (feathers not directly used in flight) are fringed white, forming a wing patch. Although the tail is mostly black, the outermost three or four retrices (flight feathers) are tipped orange, forming a T shape. Adult females, by contrast, have grey-brown upperparts, duller yellow on the breast and underparts, and an olive crown. Some females may also have a dark throat patch, similar (but less extensive) to the one found in adult males; in all cases females lack the black eye-line present in adult males. It is hypothesized that females with throat patches are older individuals.
Following the general pattern observed among icterids, the overall plumage pattern seen in immature male Bullock's orioles closely resembles that seen in adult females. Juveniles resemble adult females but have darker wings, fresh wing coverts, and a pink or whitish bill. Sexual dimorphism is not obvious in juveniles.
Both males and females rear the young and defend the nest from predators and nest parasites.
Bullock's orioles and Baltimore orioles typically hybridize in the Midwest where their geographic ranges overlap.
This bird's song is similar to that of the Baltimore Oriole, but faster and somewhat more harsh.
to Oaxaca
(Jaramillo and Burke 1999).
. They especially prefer riparian corridors
, open deciduous woodland, and scrub forest
(Jaramillo and Burke 1999). Observations during the breeding season indicate that members of this species prefer areas with an abundance of cottonwood, pecan, and (if near water) willow (Jaramillo and Burke 1999; Rising and Williams 1999). In dry areas, this species prefers salt cedar and mesquite (Rising and Williams 1999). In California, eucalyptus trees are used as major sources of nectar (Jaramillo and Burke 1999; Rising and Williams 1999).
s. They mainly eat insects, berries
and nectar.
Icterid
The Icterids are a group of small to medium-sized, often colorful passerine birds restricted to the New World. Most species have black as a predominant plumage color, often enlivened by yellow, orange or red. The family is extremely varied in size, shape, behavior and coloration...
. At one time, this species and the Baltimore Oriole
Baltimore Oriole
The Baltimore Oriole is a small icterid blackbird that averages 18 cm long and weighs 34 g. This bird received its name from the fact that the male's colors resemble those on the coat-of-arms of Lord Baltimore...
were considered to be a single species, the Northern Oriole. This bird was named after William Bullock, an English
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
amateur naturalist
Natural history
Natural history is the scientific research of plants or animals, leaning more towards observational rather than experimental methods of study, and encompasses more research published in magazines than in academic journals. Grouped among the natural sciences, natural history is the systematic study...
.
Physical description
Bullock's orioles are sexually dimorphicSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, with males being more brightly colored than females. In addition, adult males tend to be slightly larger and heavier than females. In general, adults range in mass from 29 to 43 grams. Adults have a pointed bill with a straight culmen. In adult males, the tail is long, square, and jet black. All exposed skin is black, as are the claws and bill, though the base of the lower mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
lightens to bluish-gray.
Adult males are characterized by strongly contrasting orange and black plumage, a black throat patch and a white wing bar. The underparts, breast, and face are orange or yellow; by contrast, the back, wings, and tail are black. A black line extends from each eye to the black crown. The wing coverts (feathers not directly used in flight) are fringed white, forming a wing patch. Although the tail is mostly black, the outermost three or four retrices (flight feathers) are tipped orange, forming a T shape. Adult females, by contrast, have grey-brown upperparts, duller yellow on the breast and underparts, and an olive crown. Some females may also have a dark throat patch, similar (but less extensive) to the one found in adult males; in all cases females lack the black eye-line present in adult males. It is hypothesized that females with throat patches are older individuals.
Following the general pattern observed among icterids, the overall plumage pattern seen in immature male Bullock's orioles closely resembles that seen in adult females. Juveniles resemble adult females but have darker wings, fresh wing coverts, and a pink or whitish bill. Sexual dimorphism is not obvious in juveniles.
Reproduction
Bullock's orioles are seasonally monogamous. The breeding season typically lasts from May until July. The exact timing of the beginning of the breeding season tends to vary geographically: in general, breeding begins later in the northernmost and westernmost portions of its geographic range. Mated pairs of Bullock's orioles cooperate to weave deep, pendant baskets in which are deposited between three and six eggs, though females tend to do much of the work. The nest is woven of plant fibers, primarily bark and fine grass fiber, though animal hair is also commonly used. The nest is lined with down, hair, and moss.Both males and females rear the young and defend the nest from predators and nest parasites.
Bullock's orioles and Baltimore orioles typically hybridize in the Midwest where their geographic ranges overlap.
Communication
Both males and females sing. While males have a sweeter voice, females tend to be more prolific singers.This bird's song is similar to that of the Baltimore Oriole, but faster and somewhat more harsh.
Distribution
Bullock's orioles are native to western North America, though according to Jaramillo (1999) they are sometimes found as vagrants in the eastern half of the continent. During the breeding season, they are found as far west as the eastern foothills of the Cascade range. Their breeding range stretches east to the Dakotas, Kansas, and northern central Texas (Jaramillo and Burke 1999). This species can be found as far north as British Columbia in Canada and as far south as Sonora or Durango in Mexico (Jaramillo and Burke 1999; Rising and Williams 1999). It is common throughout its range, but is absent in parts of Arizona and Idaho where a combination of extreme elevation and an arid climate make for poor living conditions (Rising and Williams 1999). During winter, this species retreats to Mexico and northern Central America. Its winter range extends south and east from SinaloaSinaloa
Sinaloa officially Estado Libre y Soberano de Sinaloa is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 18 municipalities and its capital city is Culiacán Rosales....
to Oaxaca
Oaxaca
Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions...
(Jaramillo and Burke 1999).
Habitat
Like other members of Icteridae, Bullock's orioles prefer habitat edgesEcotone
An ecotone is a transition area between two biomes but different patches of the landscape, such as forest and grassland. It may be narrow or wide, and it may be local or regional...
. They especially prefer riparian corridors
Habitat corridor
A habitat corridor is a strip of land that aids in the movement of species between disconnected areas of their natural habitat. An animal’s natural habitat would typically include a number of areas necessary to thrive, such as wetlands, burrowing sites, food, and breeding grounds...
, open deciduous woodland, and scrub forest
Shrubland
Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...
(Jaramillo and Burke 1999). Observations during the breeding season indicate that members of this species prefer areas with an abundance of cottonwood, pecan, and (if near water) willow (Jaramillo and Burke 1999; Rising and Williams 1999). In dry areas, this species prefers salt cedar and mesquite (Rising and Williams 1999). In California, eucalyptus trees are used as major sources of nectar (Jaramillo and Burke 1999; Rising and Williams 1999).
Diet
These birds forage in trees and shrubs, also making short flights to catch insectInsect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s. They mainly eat insects, berries
Berry
The botanical definition of a berry is a fleshy fruit produced from a single ovary. Grapes are an example. The berry is the most common type of fleshy fruit in which the entire ovary wall ripens into an edible pericarp. They may have one or more carpels with a thin covering and fleshy interiors....
and nectar.
Related species
A member of the northern oriole group, Bullock's orioles were once considered to be conspecific with Baltimore orioles and Black-backed orioles. However, recent phylogenetic data suggest that Bullock's orioles are members of a distinct species that does not share a most-recent common ancestor with Baltimore orioles, as was once assumed.External links
- Bullock's Oriole Information - South Dakota Birds and Birding
- Bullock's Oriole Species Account - Cornell Lab of Ornithology
- Bullock's Oriole Species Account - Encyclopedia of Life
- Bullock's Oriole - Icterus bullockii - USGS Patuxent Bird Identification InfoCenter
- Bullock's Oriole (BirdHouses101.com)