Agelaius tricolor

Geographic Range

Tricolored blackbirds ( Agelaius tricolor ) are found in western coastal North America. They are native to California and parts of Oregon, Washington, and Nevada. Highest concentrations are found in the Central and San Joaquin Valleys of California, as well as coastal areas.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Tricolored blackbirds are found in areas near water, such as marshes, grasslands, and wetlands. They require some sort of substrate nearby to build nests. This substrate is often in the form of aquatic vegetation. They also need foraging areas, which can consist of grassland or agricultural pastures such as rice, grain, or alfalfa.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial
• freshwater freshwater

• Terrestrial Biomes
• savanna or grassland savanna or grassland

• Wetlands
• marsh marsh

• Other Habitat Features
• agricultural agricultural

Physical Description

Tricolored blackbirds exhibit sexual dimorphism. Males are larger than females and possess dark red shoulder patches with white median coverts on the wings, giving the species its name. Males have brown plumage in the fall. Females are shades of gray with a lighter gray throat. One way to distinguish them from female red-winged blackbirds is that they tend to be darker, have more pointed wingtips, and have more slender bills. They are about 22 cm long with a 35.5 cm wingspan. They weigh approximately 59.5 grams.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• male more colorful

Reproduction

Males attract females by singing and displaying courtship behaviors. The species exhibits polygyny, one male may breed with 1 to 4 females.

• Mating System
• polygynous polygynous

Tricolored blackbirds breed in both the spring and fall. Tricolored blackbirds exhibit itinerant breeding, meaning that they breed twice a year in two separate locations. Spring breeding takes place in mid-March through late April. Breeding colonies consisting of up to 200,000 nests. Clutch sizes in both breeding seasons ranged between one and four. The most common clutch size is three. Incubation lasts between 11 and 14 days. Females build nests and lay their eggs in approximately one week. Females also take part in incubating the young. Fledging occurs approximately 9 days after the chicks are born. An additional 15 days or so are required for the young to live away from their parents. Males begin to breed when they are two years of age. Females are able to breed when they are one year of age.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Males and females care for the young. Females remain at nests during the daytime to incubate the eggs. Males care for the young after they hatch. They range up to 6.5 km to acquire food for nestlings.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • male
  • protecting
    • male
    • female

Lifespan/Longevity

Not much is known about the lifespan of tricolored blackbirds due to few banded recoveries. They can live up to 13 years. Predation and harsh weather conditions account for the majority of mortality. Further studies on survivorship need to be conducted.

Behavior

Tricolored blackbirds are the most colonial species of all North American passerines. They gather in large flocks outside of the breeding season and seasonally migrate among different areas.

• Key Behaviors
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• social social
• colonial colonial

Home Range

Males display territoriality. Generally, each territory is about 10.7 square meters, containing several nests. Foraging takes place far from their nests.

Communication and Perception

Tricolored blackbirds have a nasal “oo-grreee” call that begins loud and gradually gets softer. They also emit a “drdodrp” call. Their calls have a lower pitch than those of red-winged blackbirds ( Agelaius phoeniceus ). Females tend to be silent during incubation.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Tricolored blackbirds are omnivorous, feeding on both animal and plant matter. Their diet depends on the region they live in and what crops or insects are most abundant. Insect prey includes grasshoppers , beetles , moths , and fly larvae . Their diet also includes grains, seeds, rice, and other crops. Nestlings are fed primarily insects.

• Primary Diet
• omnivore omnivore

• Animal Foods
• insects

• Plant Foods
• seeds, grains, and nuts
• fruit

Predation

Tricolored blackbirds are preyed on by a variety of species. Predators include mammals such as gray foxes ( Urocyon cinereoargentus ) and skunks ( Mephitis mephitis ). Larger birds, such as common ravens ( Corvus corax ), black-crowned night herons ( Nycticorax nycticorax ), northern harriers ( Circus cyaneus ) and Cooper’s hawks ( Accipiter cooperii ) also prey on tricolored blackbirds. In more urban areas, feral cats ( Felis catus ) prey on nests. Tricolored blackbirds do not fight back against predators and tend to be less aggressive than red-winged blackbirds .

Ecosystem Roles

Many tricolored blackbirds are dependent on rice-growing fields and duck-hunting areas of central California. Their populations change in response to insect abundances. They are ecologically dependent on insect outbreaks for food. Thus, they help to keep rampant insect populations under control.

Economic Importance for Humans: Positive

Tricolored blackbirds help manage insect populations that harm crops. They are especially significant during insect outbreak years where insects such as grasshoppers are in high abundance. By feeding on agriculturally harmful insects, higher crop yields can be obtained.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

Tricolored blackbirds are also considered agricultural pests because they often forage in nearby croplands. They can feed on young rice grains, oats, and barley.

• Negative Impacts
• crop pest

Conservation Status

Tricolored blackbirds are federally protected under the Migratory Bird Treaty Act of 1918. They are listed as endangered bu the International Union for Conservation of Nature and Natural Resources (IUCN) Red List. The California Department of Fish and Game lists tricolored blackbirds as Species of Special Concern. Population declines are due to loss of wetland habitat, urban sprawl, and agricultural needs. This has resulted in greatly reduced foraging and breeding areas. Several conservation efforts are underway to preserve this species. Tricolored blackbird habitat development on public land and colony preservation can help stimulate populations. Education and outreach is important for educating landowners on proper ways to coexist with the tricolored blackbirds. Continued tracking is helping researchers understand breeding and migrating behaviors of this species so that more precise conservation plans can be made.

Additional Links

Encyclopedia of Life

Contributors

Carolina Fernandez (author), Florida State University, Emily DuVal (editor), Florida State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Beedy, E., W. Hamilton. 1999. The Birds of North America . Philadelphia, PA: The Birds of North America, Inc..

Hamilton, W. 1998. Tricolored Blackbird itinerant breeding in California. Condor , 100: 218-226.

Orians, G. 1960. Autumnal breeding in the Tricolored Blackbird. Auk , 77: 379-398.

Sibley, D. 2007. The Sibley Guide to Birds . New York: Alfred A. Knopf, Inc..

Skorupa, J., R. Hothem, R. DeHaven. 1980. Foods of breeding Tricolored Blackbirds in agricultural areas of Merced County. Condor , 82: 465-467.

U.S. Fish and Wildlife Service and California Department of Fish and Game. Tricolored Blackbird status update and management guidelines. 97-099. Sacramento, CA.: E.C. Beedy and W.J. Hamilton III. 1997.