Tricoloured blackbird (Agelaius tricolor)

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Male tricoloured blackbird in breeding plumage
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Tricoloured blackbird fact file

Tricoloured blackbird description

KingdomAnimalia
PhylumChordata
ClassAves
OrderPasseriformes
FamilyIcteridae
GenusAgelaius (1)

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).

Size
Length: 18 – 24 cm (2)
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Tricoloured blackbird 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).

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Tricoloured blackbird 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).

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Tricoloured blackbird habitat

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).

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Tricoloured blackbird status

Classified as Endangered (EN) on the IUCN Red List (1).

IUCN Red List species status – Endangered

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Tricoloured blackbird threats

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).

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Tricoloured blackbird 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).

View information on this species at the UNEP World Conservation Monitoring Centre.
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Find out more

To learn more about the conservation of the tricoloured blackbird visit:

For more information on this and other bird species please see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Gregarious
Tending to form a group with others of the same species by habitually living or moving in flocks or herds rather than alone.
Territory
An area occupied and defended by an animal, a pair of animals or a colony.
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References

  1. IUCN Red List (October, 2008)
    http://www.iucnredlist.org
  2. BirdLife International (October, 2008)
    http://www.birdlife.org
  3. Cook, L.F. and Toft, C.A. (2005) Dynamics of extinction: population decline in the colonially nesting tricolored blackbird Agelaius tricolor. Bird Conservation International, 15: 73 - 88.
  4. Tricolored Blackbird Portal (October, 2008)
    http://tricolor.ice.ucdavis.edu/node/547
  5. Hamilton, W.J. (2004) Tricolored blackbird (Agelaius tricolor). In: The Riparian Bird Conservation Plan: A Strategy for Reversing the Decline of Riparian-Associated Birds in California. California Partners in Flight, California. Available at:
    http://www.prbo.org/calpif/htmldocs/species/riparian/tricolored_blackbird.htm
  6. Tricolored Blackbird Working Group. (2007) Conservation Plan for the Tricolored Blackbird (Agelaius tricolor). Sustainable Conservation, San Francisco. Available at:
    http://www.nbii.gov/portal/community/Communities/Ecological_Topics/Bird_Conservation/USFWS_Focal_Species/Tricolored_Blackbird
  7. The Center for Biological Diversity (October, 2008)
    http://www.biologicaldiversity.org/species/birds/tricolored_blackbird
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Image credit

Male tricoloured blackbird in breeding plumage  
Male tricoloured blackbird in breeding plumage

© Ian Tait / naturalvisions.co.uk

Natural Visions
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GU9 8HJ
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Tel: +44 (0) 1252 716 700
Fax: +44 (0) 1252 727 464
info@naturalvisions.co.uk
http://www.naturalvisions.co.uk/

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