Overview

Brief Summary

Biology

Although highly social throughout the year, the tricoloured blackbird's gregarious behaviour becomes most apparent during the breeding season (April to July), when huge colonies may form, consisting of tens of thousands of birds (2) (3). Within the vast colony, many activities are remarkably synchronous, such as nesting, foraging and the males' singing (5). Breeding pairs, which only stay together for a single nesting effort, maintain a small territory of a few square metres around their nest (4). The female tricoloured blackbird builds the nest alone, collecting dry leaves which are dipped in water and woven around strong, upright plant stems, usually around a metre above the ground. A layer of mud and softer materials is then added to help cushion the clutch of three to five eggs, which are incubated by the female for around 12 days. After hatching, the chicks are fed by both parent birds for 10 to 14 days before fledging. Interestingly, adults encourage the fledglings to disperse from the colony by tempting them with food, and then fly away from the colony with the young bird in pursuit (4). Despite feeding mainly upon grains, the tricoloured blackbird is opportunistic and will take a variety of other foods when available, such as insects (particularly grasshoppers) and snails (2) (4). This species usually only forages within five to six kilometres from the colony, hence the proximity of good foraging sites is one of the requirements for colony formation (6). During the winter, the tricoloured blackbird roosts and forages communally, and many colonies withdraw from their breeding grounds and concentrate around the central coast of California and the Sacramento-San Joaquin Delta (4).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Description

Despite forming the largest breeding colonies of any North American landbird, the tricoloured blackbird's numbers are rapidly declining (3). The common name of this species derives from the male's plumage, which is almost entirely black, except for patches on the upper wing, near the shoulders, which are bright scarlet with a band of white below. By contrast, the female has predominantly dark brown plumage, which is paler around the throat, and streaked dark grey and brown on the underparts (2) (4). Both sexes possess long, pointed bills and narrow, pointed wings. Juveniles resemble the female adult, although their colouring is paler (4). The tricoloured blackbird produces a range of vocalisations including the male's drawn-out guuuaaaak call, a chwuk alarm call and a churr flight call (2). The male also makes a curious mewing call during the early part of the breeding season (4).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Distribution

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 (Native )

  • Hamilton, W. 1998. Tricolored Blackbird itinerant breeding in California. Condor, 100: 218-226.
  • 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.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Range Description

Agelaius tricolor is near-endemic to California, breeding mainly in the Central Valley and other points west of the Cascades and Sierra Nevada, U.S.A. It has also been recorded in Oregon, west Nevada (Jaramillo and Burke 1999), Washington (Beedy and Hamilton 1999), and extreme northwest Baja California (Mexico). It has a large range, with an estimated global Extent of Occurrence of 113,000 km2, which has not contracted since the 1930s. Californian birds are thought to make up over 95% of the global population (Cook and Toft 2005). In 1934, systematic surveys estimated over 700,000 adults in just 8 Californian counties, and found breeding birds in 26 counties, including one colony containing over 200,000 nests (c.300,000 adults) covering 24 ha (Neff 1937). Studies in 1969-1972 reported an average of about 133,000 individuals/year in Central Valley, and estimated that the global population had declined by more than 50% since 1934 (DeHaven et al. 1975). Censuses conducted throughout California in 1994, 1997 and 2000 gave figures of 370,000, 233,000 and 162,000 individuals respectively (Beedy and Hamilton 1999, Cook and Toft 2005), equating to a decline of 56% in six years. However, state-wide volunteer-based censuses conducted throughout California located 257,000 individuals attending 121 breeding colonies in 2005 (King et al. 2006), 394,858 in 180 sites in 32 counties in 2008 (Kelsey 2008) and 259,322 at 138 sites in 29 counties in 2011 (Kelsey 2011). These results suggest that recent declines may not have been as severe as previous estimates reported, but that steep declines (almost 35%) occurred between 2008 and 2011. These apparent declines may be due to discrepancies in survey methodology, but are likely to be partly caused by low reproductive success that has been documented in reports over the past three years (Meese 2008, 2009a, 2009b). The Christmas Bird Count has recorded the species regularly at 120 sites over a 39 year period, and that data suggests the population may be relatively stable (G. Butcher in litt. 2006). This species has proven very difficult to sample, as confirmed by the considerable variation in population estimates. To clarify its status, a thorough, unbiased and consistent approach to sampling is needed in the future.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

occurs (regularly, as a native taxon) in multiple nations

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Breeding range extends from central southern Oregon south through interior California, and along the coast from central California south to localized areas in northwestern Baja California. Abundance is highest in central and central northern California (Breeding Buird Survey data); most of the largest colonies are in the Central Valley (Beedy and Hamilton 1999). During the nonbreeding period the range contracts somewhat as the species withdraws from several areas around the margins of the breeding range (Beedy and Hamilton 1999).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Range

Marshes and farmlands of sw Oregon to nw Baja California.
  • Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2014. The eBird/Clements checklist of birds of the world: Version 6.9. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Range

A North American species, over 95 percent of the tricoloured blackbird's global population is found in California, with the remainder found in Oregon, west Nevada, Washington, and extreme north-west Baja California (2). In California, the population is divided into two main regions, a southern California population, found south of the Tehachapi Mountains, and a Central Valley population (4).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Physical Description

Morphology

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.

Average mass: 59.5 g.

Average length: 22.2 cm.

Average wingspan: 35.5 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; male more colorful

  • Sibley, D. 2007. The Sibley Guide to Birds. New York: Alfred A. Knopf, Inc..
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Size

Length: 22 cm

Weight: 68 grams

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Diagnostic Description

Males differ from male red-winged blackbirds by having a darker red shoulder patch with a white or buffy-white border (buff-yellow or absent in redwing); females are much darker than most races of the redwing and differ from first-year male redwings in lacking a large red shoulder patch; also, females have a bill that is thicker at the base and more sharply pointed (Peterson 1990).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Type Information

Type for Agelaius tricolor
Catalog Number: USNM A2836
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Male; Adult
Preparation: Skin: Whole
Collector(s): T. Nuttall
Year Collected: 1836
Locality: Santa Barbara, California, United States, North America
  • Type: Audubon. 1837. Birds Of America (Folio). 4: pl. 388, fig. 1.
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds

Source: National Museum of Natural History Collections

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Ecology

Habitat

California Central Valley Grasslands Habitat

This taxon is found in the California Central Valley grasslands, which extend approximately 430 miles in central California, paralleling the Sierra Nevada Range to the east and the coastal ranges to the west (averaging 75 miles in longitudinal extent), and stopping abruptly at the Tehachapi Range in the south. Two rivers flow from opposite ends and join around the middle of the valley to form the extensive Sacramento-San Joaquin Delta that flows into San Francisco Bay.

Perennial grasses that were adapted to cool-season growth once dominated the ecoregion. The deep-rooted Purple Needle Grass (Nassella pulchra) was particularly important, although Nodding Needle Grass (Stipa cernua), Wild Ryes (Elymus spp.), Lassen County Bluegrass (Poa limosa), Aristida spp., Crested Hair-grass (Koeleria pyramidata), Deergrass (Muhlenbergia rigens,), and Coast Range Melicgrass (Melica imperfecta) occurred in varying proportions. Most grass growth occurred in the late spring after winter rains and the onset of warmer and sunnier days. Interspersed among the bunchgrasses were a rich array of annual and perennial grasses and forbs, the latter creating extraordinary flowering displays during certain years. Some extensive mass flowerings of the California Poppy (Eschscholzia californica), Lupines (Lupinus spp.), and Exserted Indian Paintbrush (Castilleja exserta) are found in this grassland ecoregion.

Prehistoric grasslands here supported several herbivores including Pronghorn Antelope (Antilocapra americana), elk (including a valley subspecies, the Tule Elk, (Cervus elaphus nannodes), Mule Deer (Odocoileus hemionus), California ground squirrels, gophers, mice, hare, rabbits, and kangaroo rats. Several rodents are endemics or near-endemics to southern valley habitats including the Fresno Kangaroo Rat (Dipodomys nitratoides exilis), Tipton Kangaroo Rat (Dipodomys nitratoides nitratoides), San Joaquin Pocket Mouse (Perognathus inornatus), and Giant Kangaroo Rat (Dipodomys ingens). Predators originally included grizzly bear, gray wolf, coyote, mountain lion, ringtail, bobcat, and the San Joaquin Valley Kit Fox (Vulpes velox), a near-endemic.

The valley and associated delta once supported enormous populations of wintering waterfowl in extensive freshwater marshes. Riparian woodlands acted as important migratory pathways and breeding areas for many neotropical migratory birds. Three species of bird are largely endemic to the Central Valley, surrounding foothills, and portions of the southern coast ranges, namely, the Yellow-billed Magpie (Pica nuttalli), the Tri-colored Blackbird (Agelaius tricolor EN), and Nuttall’s Woodpecker (Picoides nuttallii).

The valley contains a number of reptile species including several endemic or near-endemic species or subspecies such as the San Joaquin Coachwhip (Masticophis flagellum ruddocki), the Blunt-nosed Leopard Lizard (Gambelia sila EN), Gilbert’s Skink (Plestiodon gilberti) and the Sierra Garter Snake (Thamnophis couchii). Lizards present in the ecoregion include: Coast Horned Lizard (Phrynosoma coronatum NT); Western Fence Lizard (Sceloporus occidentalis); Southern Alligator Lizard (Elgaria multicarinata); and the Northern Alligator Lizard (Elgaria coerulea).

There are only a few amphibian species present in the California Central Valley grasslands ecoregion. Special status anuran taxa found here are: Foothill Yellow-legged Frog (Rana boylii NT); Pacific Chorus Frog (Pseudacris regilla); and Western Spadefoot Toad (Pelobates cultripes). The Tiger Salamander (Ambystoma tigrinum) occurs within this ecoregion.

Although many endemic plant species are recognized, especially those associated with vernal pools, e.g. Prickly Spiralgrass (Tuctoria mucronata). A number of invertebrates are known to be restricted to California Central Valley habitats. These include the Delta Green Ground Beetle (Elaphrus viridis CR) known only from a single vernal pool site, and the Valley Elderberry Longhorn Beetle (Desmocerus californicus dimorphus) found only in riparian woodlands of three California counties.

Vernal pool communities occur throughout the Central Valley in seasonally flooded depressions. Several types are recognized including valley pools in basin areas which are typically alkaline or saline, terrace pools on ancient flood terraces of higher ground, and pools on volcanic soils. Vernal pool vegetation is ancient and unique with many habitat and local endemic species. During wet springs, the rims of the pools are encircled by flowers that change in composition as the water recedes. Several aquatic invertebrates are restricted to these unique habitats including a species of fairy shrimp and tadpole shrimp.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© World Wildlife Fund & C. Michael Hogan

Supplier: C. Michael Hogan

Trusted

Article rating from 1 person

Average rating: 5.0 of 5

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 ; terrestrial ; freshwater

Terrestrial Biomes: savanna or grassland

Wetlands: marsh

Other Habitat Features: agricultural

  • Beedy, E., W. Hamilton. 1999. The Birds of North America. Philadelphia, PA: The Birds of North America, Inc..
  • Orians, G. 1960. Autumnal breeding in the Tricolored Blackbird. Auk, 77: 379-398.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Habitat and Ecology

Habitat and Ecology
It is a lowland species, but has bred to 1,300 m in the Klamath area (Oregon) and along the west side of the Sierras (Beedy and Hamilton 1999). It breeds in freshwater marshes with tall emergent vegetation, in upland habitats (especially thickets of non-native Himalayan blackberry Rubus discolor), and in silage fields (Jaramillo and Burke 1999, Cook and Toft 2005), with 50% of the birds in California during the 2008 statewide survey observed nesting in silage fields (Kelsey 2008). It forages in agricultural areas, particularly where livestock are present and grass is short, and shows a preference for roosting in marshes (Jaramillo and Burke 1999). An opportunistic forager, the species takes any locally abundant insect including grasshoppers (Orthoptera), beetles and weevils (Coleoptera), caddis fly larvae (Trichoptera), moth and butterfly larvae (Lepidoptera), dragonfly larvae (Odonata), and lakeshore midges (Diptera), as well as grains, snails, and small clams (Beedy and Hamilton 1999). Breeding typically occurs between April and July, when individuals congregate to form massive breeding colonies that are larger than those of any other extant North American landbird following the extinction of the Passenger Pigeon Ectopistes migratorius (Cook and Toft 2005). Reproductive success is significantly higher in non-native upland vegetation (primarily Himalayan blackberry) than it is in native wetland vegetation (cattail Typha spp. and bulrush Scirpus spp.), its predominant historic breeding habitat (Cook and Toft 2005). In silage fields, which hold a significant proportion of the breeding population (17% in 2000), reproductive success can be disastrously low, as harvesting can result in the loss of entire colonies with tens of thousands of nests (Cook and Toft 2005). Although it can be found throughout the breeding range during winter, the species is nevertheless partly migratory, with large numbers of birds being seen along the central Californian coast in the winter even though few nest in this area in the summer (Jaramillo and Burke 1999).


Systems
  • Terrestrial
  • Freshwater
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Comments: Breeding habitat includes freshwater marshes of cattails, tule, bulrushes, and sedges (AOU 1983). Nests are in vegetation of marshes or thickets, sometimes on the ground. Historically this species was strongly tied to emergent marshes; in recent decades much nesting has shifted to non-native vegetation (e.g., Himalayan blackberry). In migration and winter these blackbirds inhabit open cultivated lands and pastures as well as marshes (AOU 1983).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Historically, the tricoloured blackbird bred in lowland freshwater marshes. Today, as much of this species' wetland habitat has been converted for agriculture, it can more commonly be found nesting in grain silage, as well as in thickets of the non-native Himalyan blackberry (Rubus discolor) in upland regions (3).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Generally this species withdraws from the northern tip of the breeding range for winter.

Foraging occurs in flocks that range widely to more than 15 kilometers from the nesting colony (Beedy and Hamilton 1999).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Trophic Strategy

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.

Animal Foods: insects

Plant Foods: seeds, grains, and nuts; fruit

Primary Diet: omnivore

  • Skorupa, J., R. Hothem, R. DeHaven. 1980. Foods of breeding Tricolored Blackbirds in agricultural areas of Merced County. Condor, 82: 465-467.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Comments: Insects (e.g., beetles, caterpillars) comprise a large portion of the diet. Diet includes seeds and grain in fall and winter.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Associations

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.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

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.

Known Predators:

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 - 300

Comments: This species is represented by a large number of nesting colonies, but most individuals may be concentrated in a very few. For example, in the 1990s, 60 percent were concentrated in the ten largest colonies (Hamilton et al. 1995; Beedy and Hamilton 1997; Hamilton 2000). Additionally, many individuals may concentrate into relatively few winter roosts.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Abundance

100,000 - 1,000,000 individuals

Comments: Total adult population size in the mid-2000s was approximately 260,000 (Tricolored Blackbird Working Group 2007).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

General Ecology

These birds are highly gregarious. They roost and forage in flocks (Beedy and Hamilton 1999).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life History and Behavior

Behavior

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 ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life Expectancy

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.

Range lifespan

Status: wild:
13 (high) years.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Lifespan, longevity, and ageing

Maximum longevity: 13.2 years (wild) Observations: Females breed in first year; males apparently defer breeding until at least second year (http://bna.birds.cornell.edu/).
Creative Commons Attribution 3.0 (CC BY 3.0)

© Joao Pedro de Magalhaes

Source: AnAge

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

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

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.

Breeding interval: Breeding intervals are not reported.

Breeding season: Breeding can occur in spring and in fall.

Range eggs per season: 1 to 4.

Average eggs per season: 3.

Range time to hatching: 11 to 14 days.

Average fledging age: 9 days.

Average time to independence: 14 days.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 2 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; 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 ; male 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)

  • 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.
  • 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.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Nesting occurs in April-June. Males defend small territories within colonies and mate with 1-4 females. Clutch size is 3-4. Incubation, by female, lasts about 11 days (Terres 1980). Both parents feed young. Young leave nest 13 days after hatching. Two broods/year. Nests in large colonies (up to thousands of individuals). These blackbirds are itinerant breeders; they may nest more than once at different locations during a single breeding season (Beedy and Hamilton 1999). They often change nesting locations from year to year. Hamilton et al. 1995) found that 19 of 72 colonies (1991-1994) were active the following year (Hamilton et al. 1995). Of 75 colonies active in 1997, 19 were within 500 meters of colonies active in 1994 (Beedy and Hamilton 1997).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Molecular Biology and Genetics

Molecular Biology

Barcode data: Agelaius tricolor

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 2 barcode sequences available from BOLD and GenBank.

Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

NNNNNNNNNNNTTTTCGGTGCATGAGCCGGNATAGTAGGTACCGCCCTAAGCCTCCTCATCCGAGCAGAACTAGGCCAACCTGGAGCCCTTCTAGGAGACGATCAAGTTTACAACGTAGTTGTCACGGCCCATGCTTTCGTAATAATCTTCTTCATAGTCATGCCAATTATAATCGGAGGGTTCGGAAACTGACTAGTTCCTCTAATAATCGGAGCCCCCGACATAGCATTCCCACGAATAAACAACATAAGCTTCTGACTACTTCCACCATCCTTCCTCCTCCTCCTGGCATCCTCCACAGTTGAAGCAGGCGTAGGCACAGGCTGAACAGTGTATCCCCCACTAGCAGGCAACCTAGCTCACGCCGGAGCCTCAGTCGACCTTGCAATCTTCTCCCTACACCTAGCCGGTATCTCTTCAATCCTAGGAGCAATCAACTTTATTACAACAGCAATCAACATGAAACCCCCTGCCCTCTCACAATACCAAACCCCCCTATTCGTTTGATCCGTACTGATCACTGCAGTGCTATTACTTCTATCTCTACCCGTCCTCGCCGCAGGGATCACAATACTTCTCACAGACCGTAACCTCAACACCACATTCTTTGACCCTGCCGGAGNAGGAGACCCCGTACTATACCAACACCTGTTCTGNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
-- end --

Download FASTA File

Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Statistics of barcoding coverage: Agelaius tricolor

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

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.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: endangered

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
A2bc+3bc+4bc

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s
Bond, M., Butcher, G., Cook, L. & Cook, R.

Justification
This colonially breeding species is listed as Endangered because available information indicates that it is undergoing very rapid declines owing to loss of its upland nesting habitat, low reproductive success in native habitats and complete breeding failure in harvested agricultural fields. A possible reduction in the rate of decline would lead to the species being downlisted to a lower threat category if confirmed.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

National NatureServe Conservation Status

United States

Rounded National Status Rank: N3 - Vulnerable

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

NatureServe Conservation Status

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Nests in colonies primarily in California; historically more numerous than at present; now relatively stable, but vulnerable to localized habitat loss and degradation from agricultural practices, urbanization, or inappropriate water management, and vulnerable to reduced reproductive success from impacts of native predators.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Status

Classified as Endangered (EN) on the IUCN Red List (1).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Population

Population
Rich et al (2003)

Population Trend
Decreasing
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Short Term Trend: Relatively stable (=10% change)

Comments: Trend over the past 10 years or three generations is uncertain but probably relatively stable. Range-wide Breeding Bird Survey (BBS) data indicate an average annual increase of 2.9 percent (95% CI = -0.2, 5.2) for 1966-2011 and 3.3 percent (95% CI = -2.5, 8.0) for 2001-2011. During 1966-2011, most of the range in central and southern California had an increasing trend, whereas a decreasing trend was evident north of central California and in a portion of central California (BBS data). However, the BBS methodology is regarded as not adequate for monitoring tricolored blackbird population size and distribution (see Beedy 2008).

California statewide totals of adults in four late-April surveys covering all recently known colony sites were: 369,359 (1994); 237,928 (1997); 104,786 (1999); and 162,508 (2000). A statewide census in 2005 indicated a California population of approximately 260,000 (Tricolored Blackbird Working Group 2007)..

Global Long Term Trend: Decline of 30-70%

Comments: Overall range of the species has changed little since the mid-1930s, but breeding no longer occurs in some historical locations (e.g., parts of northwestern Baja California), and in some areas formerly large populations are now much smaller (Beedy and Hamilton 1999). Overall population is greatly reduced from that observed by Neff (1937) during the 1930s (Tricolored Blackbird Working Group 2007).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Threats

Major Threats
Loss of upland nesting habitat, combined with low reproductive success in native habitats and complete breeding failure in harvested agricultural fields, are the most likely causes of recent declines (Cook and Toft 2005). Additionally, herbicide spraying and contaminated water are suspected to have caused complete breeding failure in several colonies (Beedy and Hamilton 1999). Historic declines may have occurred because of the loss of native wetlands (which have declined in area by over 95% since the arrival of Europeans), loss of grasslands and grasshoppers (a main component of the species's diet), hunting, and large-scale poisoning efforts to control crop depredation that continued until the 1960s (Neff 1937, DeHaven et al. 1975, Cook and Toft 2005). Predation by non-native Cattle Egret Bubulcus ibis appears to be a significant threat in California (L. Cook in litt. 2012). Some birds are shot in the rice-growing regions of northern Central Valley (L. Cook in litt. 2012). Losses of formerly productive foraging habitats to perennial, woody crops (primarily almonds and grapes) and to urbanisation are also serious threats. Because breeding success is so poor in native wetlands, protection of these habitats will not reverse population declines in the species: conservation measures must focus on agricultural land and upland habitats as well (DeHaven et al. 1975).

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Degree of Threat: High - medium

Comments: The species has undergone a long-term population decline, primarily due to losses and fragmentation of breeding and foraging habitats caused by urban and agricultural land conversions, and water diversions (Tricolored Blackbird Working Group 2007). Most of California's formerly extensive freshwater wetlands have been lost, and the remaining ones often are small isolated patches that support high densities of predators (e.g., coyote, raccoon, black-crowned night-heron, common raven; great-tailed grackle in southern California), which sometimes may cause significant reductions in blackbird reproductive success through predation or disturbance (Tricolored Blackbird Working Group 2007).

Inappropriate water management sometimes causes nesting failures if managed water levels are too shallow (not deep enough to deter raccoon and other predators) or too deep (flooding nests, such as has occurred at Lake Isabella) (Tricolored Blackbird Working Group 2007).

Losses of formerly productive foraging habitats (especially those within 5-6 kilometers of breeding colony sites) to perennial, woody crops (primarily almonds and grapes) and to urbanization are serious threats (Tricolored Blackbird Working Group 2007). In addition, untimely harvesting of silage grains in locations where colonies have settled causes complete breeding failure of many thousands of birds for at least one breeding attempt (Cook and Toft 2005).

Concentration of a high proportion of the population in a few breeding colonies increases the risk of major reproductive failures, especially in vulnerable habsuch as active agricultural fields (Beedy 2008)..

Despite localized threats to habitat and from predators, USFWS (2006) concluded that these factors do not represent significant threats to the continued existence of the species. USFWS (2006) also found that contaminants and other factors do not pose significant threats.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Historically, the tricoloured blackbird's population underwent a serious decline, primarily due to habitat loss as a result of urbanisation, conversion of land for agriculture and the draining of wetlands. In addition, hunting of this species for sale at markets and deliberate poisoning to safeguard crops, were both extensively practiced up until their ban in 1970s and 1980s (4). Despite losing a great deal of its native habitat, the tricoloured blackbird has adapted, and today large numbers breed in silage and in upland regions (3). Unfortunately, in these environments this species faces new threats, as many colonies are being decimated by herbicide poisoning, predation and, in particular, silage harvesting. The silage harvest takes place while the tricoloured blackbird is laying eggs and brooding chicks, and may therefore destroy an entire colony's breeding efforts. With some silage colonies comprising tens of thousands of birds, these losses represent a significant portion of this species' global population (3) (4).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Management

Conservation Actions

Conservation Actions
Conservation Actions Underway
It is currently classified in California as a Species of Special Concern and a Migratory Bird of Management Concern, categories which identify reduced populations but do not include the legal protections offered to species listed as threatened (Cook and Toft 2005). A conservation action plan for the species was published in 2007 (Tricolored Blackbird Working Group 2007). Measures have been taken at times to protect nesting colonies of the species, including purchasing portions of crops, or delaying harvest to avoid impacting nests during the active breeding season. These actions and participation by landowners resulted in the recruitment of an estimated 37,000 to 44,000 first-year adults to the 1994 and 1995 breeding seasons (Beedy and Hamilton 1999) and benefited the population in 2003. However, the U.S. Fish and Wildlife Service take the position that crop purchases or reimbursements for delayed harvest are not a feasible long-term solution for the species' management on private agricultural lands (M. Bond in litt. 2005). Management guidelines have been produced (Beedy and Hamilton 1997, DeHaven 2000). In 2008, an agreement was reached between Audubon California and a local farmer to safeguard a single colony of c.80,000 birds by delaying the harvest of 65 ha of farmland in Tulare County, California where the colony is nesting (Anon. 2008).

Conservation Actions Proposed
Maintain a viable, self-sustaining population throughout current geographic range. Avoid losses of colonies and their associated habitats and increase the breeding population on suitable public and private lands managed for this species. Enhance public awareness and support for protection of habitat and active colonies (Beedy and Hamilton 1997). Create low-risk nesting substrates such as marshes and blackberries within key dairy regions of the San Joaquin and Sacramento valleys, to provide alternative nesting sites to grain silage fields, and monitor their use (DeHaven 2000). Delay harvesting or herbicide applications until after the colony completes the breeding cycle (Beedy and Hamilton 1999). Protect and enhance Toledo Pit (Tulare County), an important breeding site (DeHaven 2000). Conduct regular range-wide censuses to monitor population trends. Initiate mark-recapture and ratio-telemetry studies to determine demographic rates such as survival, reproduction, and population growth, and site fidelity as related to reproductive success. Conduct studies of foraging ecology to determine key characteristics and possibilities to enhance foraging habitat. List the species as Endangered under federal law (M. Bond in litt. 2005).

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Biological Research Needs: Need to determine most effective non-lethal control methods for times when species is considered an agricultural pest.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Breeding colonies occur on national wildlife refuges in Klamath Basin, California and Oregon, and in the Sacramento and San Joaquin valleys, California. Some nonbreeding roost sites are probably in protected areas.

Needs: Additional protection of nonbreeding roosts may be warranted.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

Efforts to conserve the tricoloured blackbird have been made by the US Fish and Wildlife Service by either purchasing whole areas of silage from private landowners, or by paying them to delay the silage harvest long enough to allow the tricoloured blackbird to successfully breed (4). While this has been extremely beneficial for the survival of tricoloured blackbird colonies, the US Fish and Wildlife Service do not consider it to be a long-term solution for the management of this species. Other proposed measures to conserve this species, include delaying herbicide application until the tricoloured blackbird has completed its breeding cycle, and the creation of areas of marshland and blackberries within key silage nesting regions, offering a safe, alternative breeding habitat (2). The tricoloured blackbird is listed in California as a Species of Special Concern and a Migratory Bird of Management Concern, categories which help to highlight this species' decline, but do not provide the same levels of legal protection as being listed as Endangered under the Endangered Species Act (2). Hence in 2004, the non-governmental conservation organisation, The Center for Biological Diversity, petitioned the US Fish and Wildlife Service to list the tricoloured blackbird as Endangered, but was, unfortunately, unsuccessful (7). Nevertheless, in 2007, the Tricolored Blackbird Working Group, a collaboration of various conservation organisations, produced a comprehensive conservation plan for this species. With adequate funding, the actions proposed by the plan should help to ensure the survival of this fascinating species (6).
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© Wildscreen

Source: ARKive

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Relevance to Humans and Ecosystems

Benefits

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

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

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

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Risks

Stewardship Overview: Primary conservation priorities for habitat conservation and management are to: (1) maintain, enhance, and protect existing habitat suitable for nesting, foraging, and wintering activities; (2) create and restore additional protected breeding habitats to support nesting and foraging; (3) identify mechanisms for protecting nesting and foraging habitats; (4) to the extent allowable by law, survey private lands and identify largest and most vulnerable colonies; (5) encourage private landowners to protect active breeding colonies; and (6) encourage and enhance active breeding colonies on public lands (Tricolored Blackbird Working Group 2007).

Range-wide population monitoring should be conducted at least once every three years (Beedy 2008).

Better information is needed on the effects of non-native plant species and livestock grazing on tricolored blackbird habitat.

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Wikipedia

Tricolored blackbird

The tricolored blackbird (Agelaius tricolor) is a passerine bird of the family Icteridae. Its range is limited to the coastal areas of the Pacific coast of North America, from Northern California in the U.S. (with occasional strays into Oregon), to upper Baja California in Mexico.

This highly social and gregarious bird forms the largest colonies of any North American landbird, with a single breeding colony often consisting of tens of thousands of birds.

The common name is taken from the male bird's distinctive white stripes on bottom of their red shoulder patches, or "epaulets", which are visible when the bird is flying or displaying.

Despite the similar names, this bird is not related to the Old World common blackbird, which is a thrush (Turdidae).

The species' call sounds slightly more nasal than that of the red-wing's - a nasal kip and a sharp check. The male's song is a garbled on-ke-kaaangh. The bird migrates south during the colder seasons to Mexico and back to northern California during the warmer seasons.

Endangered status[edit]

In 1990 the Department of Fish and Game (DFG) of California, based on significant decline in population numbers documented in the 1980s, added the tricolored blackbird to the published list of "Bird Species of Special Concern". This classification is an "administrative designation intended to alert biologists, land managers and others to a species declining status and encourages them to provide additional management considerations". At this time the tricolored was added to the U.S. Fish and Wildlife Service (USFWS) list of Birds of Conservation Concern.

By 1991, the tricolor's breeding population had fallen to approximately thirty-five thousand adults. This prompted a petition submitted by the Yolo chapter of the National Audubon Society to the California Fish and Game Commission. The petition brought the tricolored blackbird under consideration for endangered classification. The classification was granted until the breeding season in 1992. It was then that researchers discovered a population exceeding three hundred thousand adults. A petition to withdraw the endangered classification was submitted and accepted. Conservation measures were supposed to be developed and implemented to avoid a future decline as seen before. These measures were developed, but only very limited progress was made in preventing the future decline of the tricolored blackbird. Interested groups started reconvening shortly after the year 2000. Managing groups found startling results when conducting population research.

In 2006 the tricolored blackbird was classified as Endangered by BirdLife International. Like the extinct passenger pigeon, the colonial nature of the tricolored blackbird makes it particularly vulnerable to extinction. Native grasslands once used for nesting and feeding have been lost to urban and agricultural development. Birds adapted to nesting in agricultural fields have been disturbed by harvesting during the breeding season. Once the tricolored blackbird was placed on the BirdLife Endangered Species list, it officially became a concern both regionally and nationally.

The U.S. Fish and Wildlife Service maintained the following "Primary conservation priorities for Tricolor habitat conservation and management" (The Tricolored Blackbird Working Group, 2007):

  • Maintain, enhance, and protect existing habitat suitable for nesting, foraging, and wintering activities;
  • Create and restore additional protected breeding habitats to support nesting and foraging;
  • Identify mechanisms for protecting nesting and foraging habitats;
  • To the extent allowable by law, survey private lands and identify largest and most vulnerable colonies;
  • Encourage private landowners to protect active breeding colonies; and
  • Encourage and enhance active breeding colonies on public lands.

References[edit]

Further reading[edit]

Book[edit]

  • Beedy, E. C., and W. J. Hamilton III. 1999. Tricolored Blackbird (Agelaius tricolor). In The Birds of North America, No. 423 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.

Thesis[edit]

  • Orians GH. Ph.D. (1961). The Ecology of Social Systems in the Red-Winged Blackbird (Agelaius phoeniceus) and the Tricolored Blackbird (Agelaius tricolor). University of California, Berkeley, United States—California.

Articles[edit]

  • (2003). Emergency protection sought for tricolored blackbird. J Wildl Rehabil. vol 26, no 3. p. 36-36.
  • Academy of Natural Sciences of P. (1999). Tricolored blackbird: Agelaius tricolor. Birds of North America. vol 0, no 423. p. 1-23.
  • Cook LF & Toft CA. (2005). Dynamics of extinction: population decline in the colonially nesting Tricolored Blackbird Agelaius tricolor. Bird Conservation International. vol 15, no 1. p. 73-88.
  • Crase FT & De Haven RW. (1977). Food of Nestling Tricolored Blackbirds. Condor. vol 79, no 2. p. 265-269.
  • Crase FT & Dehaven RW. (1976). Selected Bibliography on the Food Habits of North American Blackbirds. U S Fish & Wildlife Service Special Scientific Report Wildlife. vol 192, p. 1-20.
  • Crase FT & Dehaven RW. (1978). Food Selection by 5 Sympatric California USA Blackbird Species. California Fish & Game. vol 64, no 4. p. 255-267.
  • De Haven RW, Crase FT & Woronecki PP. (1975). Movements of Tricolored Blackbirds Banded in the Central Valley of California 1965-1972. Bird Banding. vol 46, no 3. p. 220-229.
  • Dehaven RW, Crase FT & Miller MR. (1974). Aging Tri Colored Blackbirds by Cranial Ossification. Bird Banding. vol 45, no 2. p. 156-159.
  • Dehaven RW, Crase FT & Woronecki PP. (1975). Breeding Status of Tricolored Blackbird, 1969-1972. Calif Fish Game. vol 61, no 4. p. 166-180.
  • Emlen JT. (1985). Morphological Correlates of Synchronized Nesting in Tricolored Blackbird Agelaius-Tricolor Colony. Auk. vol 102, no 4. p. 882-884.
  • Hamilton WJ, III. (1998). Tricolored blackbird itinerant breeding in California. Condor. vol 100, no 2. p. 218-226.
  • Holcomb LC. (1971). Nest Building and Egg Laying by Redwinged Blackbirds in Response to Artificial Manipulations. Auk. vol 88, no 1. p. 30-34.
  • Kobayashi H. (1975). Absorption of Cerebro Spinal Fluid by Ependymal Cells of the Median Eminence. In Knigge, K M et al. (Ed) Brain-Endocrine Interaction Ii the Ventricular System in Neuroendocrine Mechanisms Symposium. Shizuoka, Japan Oct 16-18, 1974 Ix+406p Illus S Karger: Basel, Switzerland; New York, NY, USA ISBN 3-8055-2176-6, p. 109-122, 1975.
  • Oota Y, Kobayashi H, Nishioka RS & Bern HA. (1974). Relationship between Neuro Secretory Axon and Ependymal Terminals on Capillary Walls in the Median Eminence of Several Vertebrates. Neuroendocrinology. vol 16, no 2. p. 127-136.
  • Palmer TK. (1976). Pest Bird Damage Control in Cattle Feedlots the Integrated Systems Approach. Proceedings of the Vertebrate Pest Conference. vol 7, p. 17-21.
  • Payne RB & Landolt M. (1970). Thyroid Histology of Tricolored Blackbirds Agelaius-Tricolor in the Annual Cycle Breeding and Molt. Condor. vol 72, no 4. p. 445-451.
  • Powell Gun. (1974). Experimental Analysis of the Social Value of Flocking by Starlings Sturnus-Vulgaris in Relation to Predation and Foraging. Animal Behaviour. vol 22, no 2. p. 501-505.
  • Rains MC, Mount JE & Larsen EW. (2004). Simulated changes in shallow groundwater and vegetation distributions under different reservoir operations scenarios. Ecol Appl. vol 14, no 1. p. 192-207.
  • Schafer EWJ & Brunton RB. (1971). Chemicals as Bird Repellents 2 Promising Agents. Journal of Wildlife Management. vol 35, no 3. p. 569-572.
  • Skorupa JP, Hothem RL & Dehaven RW. (1980). Foods of Breeding Tri Colored Blackbirds Agelaius-Tricolor in Agricultural Areas of Merced County California USA. Condor. vol 82, no 4. p. 465-467.
  • Unitt P. (2004). Effect of plumage wear on the identification of female Red-winged and Tricolored Blackbirds. Western Birds. vol 35, no 4. p. 228-230.
  • Vickers ML & Hanson RP. (1980). Experimental Infection and Serologic Survey for Selected Paramyxoviruses in Red-Winged Blackbirds Agelaius-Phoeniceus. Journal of Wildlife Diseases. vol 16, no 1. p. 125-130.
  • http://www.fws.gov/migratorybirds/CurrentBirdIssues/Management/FocalSpecies/Plans/TCBL.pdf
Creative Commons Attribution Share Alike 3.0 (CC BY-SA 3.0)

Source: Wikipedia

Trusted

Article rating from 1 person

Average rating: 2.0 of 5

Names and Taxonomy

Taxonomy

Comments: A. phoeniceus a sister taxon (AOU 1998).

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© NatureServe

Source: NatureServe

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!