tricolored blackbird (Agelaius tricolor)
The Tricolored Blackbird is a medium-sized (18-24cm total length), sexually dimorphic North American passerine (Beedy, Edward, and Hamilton III 1999). Adult males are typically larger than females, and are black with bright red and white plumage on the wing shoulder. Adult females have sooty brown-black plumage with distinct grayish streaks, a relatively white chin and throat, and a smaller reddish shoulder-patch. Banding studies indicate a lifespan of 12-13 years (DeHaven and Neff 1973, Kennard 1975).
- Beedy, Edward C. and William J. Hamilton III. 1999. Tricolored Blackbird (Agelaius tricolor), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/423
- Beedy, E. C. and W. J. Hamilton III. 1997. Tricolored Blackbird status update and management guidelines. September. (Jones & Stokes Associates, Inc. 97-099.) Sacramento, CA. Prepared for U.S. Fish and Wildlife Serv., Portland, OR, and Calif. Dept. of Fish and Game, Sacramento, CA.
- Collier, G. 1968. Annual cycle and behavioral relationships in the Red-winged and Tricolored Blackbirds of southern California. Phd Thesis. Univ. of California, Los Angeles.
- Dehaven, R. W. and J. A. Neff. 1973. Recoveries and returns of Tricolored Blackbirds, 1941-1964. West. Bird Bander 48:10-11.
- Dehaven, R. W. 1975. Plumages of the Tricolored Blackbird. West. Bird Bander 50:59-61.
- Emlen, J. T. 1941. An experimental analysis of the breeding cycle of the Tricolored Red-wing. Condor 43:209-219.
- Kennard, J. H. 1975. Longevity records of North American birds. Bird-Banding 46:55-73.
- Martin, A. C., H. S. Zim, and A. L. Nelson. 1951. American wildlife and plants: a guide to wildlife food habits. McGraw-Hill, New York.
- Neff, J. A. 1942. Migration of the Tricolored Red-wing in central California. Condor 44:45-53.
- Orians, G. H. 1960. Autumnal breeding in the Tricolored Blackbird. Auk. 77:379-398.
- Orians, G. H. 1961b. Social stimulation within blackbird colonies. Condor 63:330-337.
- Orians, G. H. 1985. Blackbirds of the Americas. Univ. of Washington Press, Seattle.
- Payne, R. 1969. Breeding seasons and reproductive physiology of Tricolored Blackbirds and Redwinged Blackbirds. Univ. Calif. Publ. Zool. 90:1-137.
- Pyle, P. 1997. Identification guide to North American birds, Part I. Slate Creek Press, Bolinas, CA.
- Skorupa, J. P., R. L. Hothem, and R. W. DeHaven. 1980. Foods of breeding Tricolored Blackbirds in agricultural areas of Merced County, California. Condor 82:465-467.
- States/US Territories in which the tricolored blackbird, Wherever found is known to or is believed to occur: California , Nevada , Oregon
- US Counties in which the tricolored blackbird, Wherever found is known to or is believed to occur: View All
- Countries in which the the tricolored blackbird, Wherever found is known to occur: Mexico
- Additional species information
|Status||Date Listed||Lead Region||Where Listed|
|Pacific Region (Region 1)||Wherever found|
» Candidate Information
|1982-12-30||Review of Vertebrate Wildlife for Listing as End. or Thr. Species|
|1985-09-18||Review of Vertebrate Wildlife; Notice of Review; 50 FR 37958-37967|
|1989-01-06||ETWP; Animal Notice of Review; 54 FR 554 579|
|1991-11-21||ETWP; Animal Candidate Review for Listing as Endangered or Threatened Species; 56 FR 58804 58836|
|1994-11-15||ETWP; Animal Candidate Review for Listing as Endangered or Threatened Species.|
» Federal Register Documents
» Conservation Plans
» Life History
Breeding colonies require a nearby source of water, suitable nesting substrate, and natural grassland, woodland, or agricultural cropland biomes in which to forage. Historically, breeding colonies had been strongly associated with emergent marshes, but more recently there has been a shift to non-natively vegetated and active agricultural areas. In the time interval of 1931-1936, 93% of breeding colonies were observed in freshwater marshland habitats dominated by cattails and bulrushes (Neff 1937). In 1994, 55% of all observed breeding colonies were associated with dairy farms as they contain all required resources (Hamilton et al. 1995).
Tricolored Blackbirds are opportunistic foragers and will consume any locally abundant food resources, including grasshoppers and many other insects, rice, grains, watergrass, snails, and small clams (Collier 1968, Martin et al. 1951, Skorupa et al. 1980). High quality foraging areas include habitats such as irrigated pastures, lightly grazed rangelands, dry seasonal pools, mowed alfalfa fields, feedlots and dairy farms (Breedy and Hamilton 1997). Like other blackbirds, the tricolored Blackbird uses its bill to expose insects hidden under rocks, within agricultural plants, or under soil and sticks (Orians 1985). Individuals will often forage in deep dense grasses and other vegetation, and will occasionally fly-catch up to 30m above breeding colonies (Beedy, Edward, and Hamilton III 1999).
Movement / Home Range
The Central Valley and surrounding foothills of California is home to over 99% of the Tricolored Blackbird populations, though breeding sites can also be found scattered throughout Oregon, Washington and Nevada (Beedy, Edward, and Hamilton III 1999). Banding studies have shown that some Tricolored Blackbird individuals will reside in Central Valley throughout the year (Neff 1942, DeHaven and Neff 1973) whereas other individuals will migrate from their first nesting sites in the San Joaquin Valley to a second nesting site located in more Northern regions, such as the Sacramento Valley, northeast California, and southern Oregon (though sightings in Oregon are rare) (Beedy and Hamilton 1997). Winter distribution and movements indicate winter turnover and mobility at roost sites; however this requires further study (Collier 1968).
Tricolored Blackbirds form the largest breeding colonies of any North American passerine, and an individual breeding colony at a single site can be made up of thousands of birds. The species is polygamous; males defend small territories within these breeding colonies and will mate with 1-4 females (Beedy, Edward, and Hamilton III 1999). Tricolored Blackbirds are itinerant breeders, meaning they will nest multiple times in multiple locations throughout the breeding season and may rear 2 or more broods in a year. The timing of breeding colony development will vary depending on the geographical location of the population, however all breeding is usually completed by late June to early August (Orians 1960, Payne 1969). Clutch size is typically 3-4 eggs but can vary from 1-5, and the estimated incubation period is 11-12 days (Payne 1969, Emlen 1941, Orians 1961b). Young are altricial at birth, hatching from the egg blind, largely naked, and with poor coordination; the young are dependent on parents until they are about 25 days old (Payne 1969).
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