Fish crow (Corvus ossifragus)

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Fish crow perched on fence
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The fish crow is known to forage in flocks of several hundred, and roosts can contain upwards of 45,000 individuals.
  • Similarly to other members of the Corvidae family, it is likely that the fish crow forms monogamous breeding pairs.
  • The male fish crow is slightly larger than the female.
  • The fish crow builds its nests in conifer, broadleaf, palm and mangrove trees.
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Fish crow fact file

Fish crow description

KingdomAnimalia
PhylumChordata
ClassAves
OrderPasseriformes
FamilyCorvidae
GenusCorvus (1)

The fish crow (Corvis ossifragus) has a glossy, iridescent all-black plumage, sturdy scaled legs and a shiny black bill (2). The sexes are alike in appearance, although the male is slightly larger than the female (2). Physically the fish crow is similar to the larger American crow (Corvus brachyrynchos), although it can be distinguished by its vocalisations (4). The fish crow has a relatively nasal voice and gives a distinctive double call (2) (5).

Size
Length: 36 - 40 cm (2)
Weight
195 - 330 g (2)
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Fish crow biology

Although it is occasionally described as a short-distance migrant, the fish crow does not truly migrate and movements are thought to be due to food availability rather than weather conditions. Similarly to other crow species, the fish crow is a highly social bird, particularly outside of the breeding season. It is known to forage in flocks of several hundred, and roosts can contain over 45,000 individuals. During the breeding season, the fish crow may congregate with conspecifics, but in much smaller groups, and roosts alongside American crows, herons and egrets. Grooming between mating pairs is frequently seen throughout the year, and the male is also known to groom large nestlings (2).

The fish crow is known to nest in solitary pairs, or in small nesting groups. It is likely that this species is monogamous, similarly to other members of the Corvidae family. Mating pairs begin building their nest between March and June and it is usually a round structure, although this is dependent on where it is placed within the tree. The nest usually takes around nine days to build and is made from freshly plucked twigs from nearby deciduous trees. Pairs are known to start building several nests at once before concentrating on one and abandoning the others. One brood of between two and six eggs is produced each breeding season and the eggs are pale bluish-green in colour and are patterned with brown markings. The female incubates the eggs while the male guards the area and will stand in the nest if the female leaves. The eggs will generally hatch after being incubated for 18 or 19 days. The young fish crows fledge the nest around five weeks after hatching, but may continue to be fed by the male and female for around a month after leaving the nest (2).

Co-operative breeding is not known among fish crows, although a third individual is often seen with a breeding pair. This third individual may help with nest-building and feeding of the brooding female and its nestlings. However, the presence of the third bird is often disruptive, and it is frequently chased away by the breeding pair. It is thought that the third individual is not a true helper and may remain close to the nest to try and mate with the incubating female (2).

The fish crow is an omnivorous species that is known to take carrion, marine invertebrates, bird and turtle eggs, young birds, insects and fruit (2) (4). The diet of an individual is heavily dependent on its location, and birds in urban areas are known to rely on human waste as one of their main food sources (2).

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Fish crow range

The fish crow is found in parts of the coastal south-eastern United States from Maine to Louisiana, as well as around rivers in Illinois and Kansas (2) (5). During winter, fish crows are likely to congregate near abundant food sources, including estuaries, rubbish dumps and farms (2) (6).

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Fish crow habitat

The fish crow is usually found close to water, including beaches and swamps, where it is able to forage (2) (5). This species generally builds its nest in conifer, broadleaf, palm and mangrove trees (2).

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Fish crow status

The fish crow is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern

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Fish crow threats

The fish crow has a very large range and a population size that has increased in the last 40 years, and is therefore not considered to be at risk of extinction (3). However, hunting of this species is permitted in some areas of the United States and this is thought to be one of the main causes of mortality (2). The fish crow is susceptible to the West Nile Virus, and only 45 percent of individuals that contract the illness are known to survive (5).

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Fish crow conservation

The fish crow is not threatened or endangered in any parts of its range, and local populations are increasing in some areas. The movement of this species into new areas may have a negative impact on other bird species (2).

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Find out more

Find out more about the fish crow:

Find out more about bird conservation in North America:

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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

Carrion
The flesh of a dead animal.
Co-operative breeding
In birds, when three or more individuals contribute towards raising a single brood at a single nest site. Non-parental helpers at the nest assist with the feeding and raising of young birds.
Deciduous
A plant that sheds its 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) and echinoderms.
Monogamous
Having only one mate during a breeding season, or throughout the breeding life of a pair.
Omnivorous
Feeding on both plants and animals.
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References

  1. IUCN Red List (June, 2014)
    http://www.iucnredlist.org/
  2. Mcgowan, K.J. (2001) Fish crow (Corvus ossifragus) In: Poole, A. (Ed.) Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/589/articles/introduction
  3. BirdLife International (June, 2014)
    http://www.birdlife.org/
  4. MobileReference (2008) Encyclopedia of North American Birds. MobileReference, Boston, Massachusetts.
  5. Kaufmann, K. (2005) Kaufman Guide to Birds of North America. Houghton Mifflin Harcourt, Boston, Massachusetts.
  6. Dunn, J.L. and Alderfer, J. (Eds.) (2006) Field Guide to the Birds of North America. National Geographic Society, Washington, D.C.
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Image credit

Fish crow perched on fence  
Fish crow perched on fence

© Neil Bowman / www.flpa-images.co.uk

FLPA - images of nature
Pages Green House
Wetheringsett
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Suffolk IP14 5QA
United Kingdom
Tel: +44 (0) 1728 861 113
Fax: +44 (0) 1728 860 222
pictures@flpa-images.co.uk
http://www.flpa-images.co.uk

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