Rusty blackbird (Euphagus carolinus)

Description

Rusty blackbird fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Rusty blackbird description

As its common name suggests, the rusty blackbird (Euphagus carolinus) is best distinguished by the rusty red-brown edges and tips to its feathers ^{(2) (3)}. An otherwise fairly indistinctive, medium-sized bird with a slender bill, the rusty blackbird is one of the least well known of the North American blackbirds ⁽³⁾.

The distinctive rusty colouration of this species is unique to the winter plumage, where it is particularly noticeable on the upperparts of the body ^{(2) (3)}. During the winter, the male rusty blackbird is characterised by the rusty edges to the tertials, and by its rusty brown crown, nape and back. The rest of the upperparts are black, while the cheeks, throat, breast and sides are lighter brown or buff ⁽³⁾. The male also has a tawny-coloured stripe above the eye ⁽²⁾. The female rusty blackbird is similar to the male, but with a conspicuous paler buff line above the eye ⁽³⁾.

In breeding plumage, the rusty colouring of this blackbird becomes less apparent, with the male becoming generally uniform dark black above ^{(2) (3)}, often with a shiny blue-green to greenish gloss ⁽³⁾. The female is generally an unassuming grey-brown ⁽²⁾, although darker above, also with a slight blue-green gloss ⁽³⁾. 

Both the male and female rusty blackbird possess striking yellow eyes and a long, square-tipped tail ⁽⁴⁾. The juvenile rusty blackbird resembles the adult, but is typically much browner and has a paler line above the eye ^{(2) (4)}. The eye of the juvenile bird is initially brown, becoming yellow in its first autumn ⁽³⁾.

The male rusty blackbird has a squeaky, bubbling song ^{(2) (4)}, comprising up to three warbled notes ending in a higher, rising note, which is aptly likened to a rusty gate creaking. The call of the rusty blackbird is usually a harsh ‘chek’ ⁽²⁾.

Size

Length: 21 - 25 cm ⁽²⁾

Wingspan: 37 cm ⁽²⁾

Weight

47 - 80 g ⁽²⁾

Rusty blackbird biology

Invertebrates are an important part of the rusty blackbird’s diet ^{(2) (3) (7)}, especially during the summer when it prefers to forage for grasshoppers and aquatic insects ⁽³⁾. However, this species is an opportunistic feeder, and will also feed on small fish and amphibians, as well as seeds, grains and small fruits ^{(2) (3) (7)}. The rusty blackbird has even been known to attack and catch other small birds, such as sparrows, robins and snipe ⁽²⁾. The rusty blackbird feeds mostly on the ground, turning over leaves and debris in the forest in search of prey. It will also wade in shallow water, probing in the mud with its bill ⁽²⁾.

The breeding season of the rusty blackbird begins in April with the building of the nest, which is typically a substantial, bulky bowl woven from twigs, grass and lichens. It is filled with wet, rotting vegetation which is daubed onto the nest framework to produce a hard casing as it dries, and is then lined with fine grass ^{(2) (3)}. The nest is built by the female ⁽³⁾, and is usually located close to water in a tree, around six metres off the ground ⁽²⁾.

Between three and six blue-green or pale greyish eggs are laid by the female rusty blackbird in May or June ^{(2) (3)}. The eggs are incubated by the female for 14 days ^{(2) (7)}. The newly-hatched chicks are completely dependent on the adults and are fed and cared for by both the male and female for around 13 days, after which the young will fledge ^{(2) (7)}.

During the breeding season, the rusty blackbird is typically found in isolated pairs, whereas in the winter it is more likely to be observed in flocks, often of mixed species, with which it feeds and roosts ⁽³⁾.

Rusty blackbird range

The rusty blackbird has the most northerly breeding range of all North American blackbirds, occurring in Alaska, Canada and the north-eastern United States ^{(3) (5)}. It is a migratory species, spending the winter in the south-eastern and mid-western United States ^{(4) (5)}.

The greatest wintering concentrations of this species are thought to centre in the Mississippi River Valley in the United States ⁽⁶⁾.

Rusty blackbird habitat

The rusty blackbird is one of only a few bird species that are restricted to wooded wetland habitats throughout the year ⁽⁶⁾.

It is highly dependent on boreal forest wetlands during the breeding season ⁽⁶⁾, occurring in wet coniferous and mixed forests from the tundra south to the fringes of deciduous forests and grasslands ⁽³⁾. This species nests close to water sources, frequenting fens, bogs, muskeg swamps, beaver ponds and streams ^{(2) (3) (4)}.

The rusty blackbird is also found primarily in wooded wetlands in winter ^{(2) (3) (4) (6)}, although it occasionally occurs in scrub habitats or pasture land, as well as open woodlands and even cultivated areas ⁽⁷⁾.

Rusty blackbird status

The rusty blackbird is classified as Vulnerable (VU) on the IUCN Red List ⁽¹⁾.

Rusty blackbird threats

The rusty blackbird has undergone a steep and fairly rapid population decline of an estimated 85 to 99 percent since 1966. However, the reasons behind the declining population remain unclear ⁽⁴⁾.

Factors causing the decline may include the destruction of boreal wetland and woodland habitats ^{(4) (5)}, which would deprive the rusty blackbird of suitable breeding sites. An alternative suggestion is that climate change has caused wetlands in the boreal forest region to dry out and the chemical composition of the habitats to change ⁽⁴⁾.

It is widely accepted that the rusty blackbird is also encountering difficulties on its wintering grounds, perhaps as a result of the loss of many wooded wetlands in the south-eastern United States ^{(5) (6)}, particularly due to the conversion of wetlands for agriculture ⁽⁶⁾. Furthermore, habitat loss may have caused the rusty blackbird to feed in more open habitats, where it is exposed to increased competition with other birds, such as the common grackle (Quiscalus quiscula) and red-winged blackbird (Agelaius phoeniceus) ⁽⁶⁾.

This species may also fall victim to control methods targeted at other blackbird species that cause damage to crops ^{(4) (8)}, such as the spraying of blackbird roosts ⁽⁵⁾. 

Rusty blackbird conservation

Despite its acute and continuing population decline, the rusty blackbird is not currently protected under the United States Endangered Species Act ⁽⁴⁾. In 2005, the International Rusty Blackbird Technical Working Group was established by the Smithsonian National Zoological Park to carry out research on this species’ population trends, and to identify potential threats, the reasons behind its long-term decline and possible courses of action to reverse the declines ⁽⁶⁾.

Additional recommended conservation measures for the rusty blackbird include working to protect areas of suitable habitat ⁽⁴⁾.

Find out more

Find out more about the rusty blackbird:

• BirdLife International - Rusty blackbird:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=9745&m=0
• Avery, M.L. (1995) Rusty blackbird (Euphagus carolinus). In: Poole, A. (Ed.) Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
  http://bna.birds.cornell.edu/bna/species/200
• Migratory Bird Center - Rusty blackbird (April, 2012)
  http://nationalzoo.si.edu/scbi/migratorybirds/research/rusty_blackbird/

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Glossary

Boreal forest

The sub-Arctic forest of the high northern latitudes that surrounds the North Pole and is mainly composed of coniferous trees.

Deciduous forest

Forest consisting mainly of deciduous trees, which shed their leaves at the end of the growing season.

Incubate

To keep eggs warm so that development is possible.

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.

Lichen

A composite organism made up of a fungus in a co-operative partnership with an alga. Owing to this partnership, lichens can thrive in harsh environments such as mountaintops and polar regions. Characteristically forms a crust-like or branching growth on rocks or tree trunks.

Muskeg swamp

A swamp or bog consisting of a mixture of water and partly dead vegetation, frequently covered by a layer of Sphagnum moss or other mosses.

Nape

The back of the neck.

Tertials

Flight feathers attached to the upper arm (humerus) of the wing.

Tundra

Treeless, grassy plains characteristic of Arctic and sub-Arctic regions. They are very cold and have little rainfall.

References

1. IUCN Red List (April, 2012)
   http://www.iucnredlist.org/
2. Cornell Lab of Ornithology: All About Birds - Rusty blackbird (April, 2012)
   http://www.allaboutbirds.org/guide/Rusty_Blackbird/lifehistory
3. Avery, M.L. (1995) Rusty blackbird (Euphagus carolinus). In: Poole, A. (Ed.) Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
   http://bna.birds.cornell.edu/bna/species/200
4. BirdLife International (April, 2012)
   http://www.birdlife.org/datazone/speciesfactsheet.php?id=9745&m=0
5. American Bird Conservancy - WatchList species account for the rusty blackbird (Euphagus carolinus) (April, 2012)
   http://www.abcbirds.org/abcprograms/science/watchlist/rusty_blackbird.html
6. Migratory Bird Center - Rusty blackbird (April, 2012)
   http://nationalzoo.si.edu/scbi/migratorybirds/research/rusty_blackbird/
7. NatureServe Explorer - Rusty blackbird (April, 2012)
   http://www.natureserve.org/explorer/servlet/NatureServe?searchSciOrCommonName=rusty+blackbird&x=10&y=8
8. Rich, T.D., Beardmore, C.J., Berlanga, H., Blancher, P.J., Bradstreet, M.S.W., Butcher, G.S., Demarest, D.W., Dunn, E.H., Hunter, W.C., Inigo-Elias, E.E., Kennedy, J.A., Martell, A.M., Panjabi, A.O., Pashley, D.N., Rosenberg, K.V., Rustay, C.M., Wendt, J.S. and Will, T.C. (2004) Partners in Flight North American Land Bird Conservation Plan. Cornell Lab of Ornithology, Ithaca. Available at:
   http://www.birdlife.org/action/science/sites/neotrops/andes/background/08_PIF4_AppendicesWEB