Lifespan, longevity, and ageing

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Maximum longevity: 14.5 years (wild)
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Brief Summary

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The Fish Crow (Corvus ossifragus) is year-round resident locally from New York and Massachusetts south along the Atlantic-Gulf Coast to southern Florida and west to southern Texas, as well as inland along major river systems. It is very common in parts of its range. Fish Crows are found around tidewater marshes, low valleys along eastern river systems, and in Baldcypress (Taxodium) swamps; in recent decades, the interior range has expanded and the northern boundary of the range has extended northward. Although in most parts of its range it is a permanent resident, in winter Fish Crows withdraw from some parts of their inland range. In the winter, Fish Crows are often seen in mixed flocks with American Crows, when they may also be found on farmland, in towns, and around garbage dumps. The Fish Crow is one of only about a dozen bird species that are endemic to the United States (i.e., found nowhere else in the world). The Fish Crow closely resembles the American Crow (Corvus brachyrhynchos), but is smaller overall and has a smaller bill, smaller feet, and shorter legs, as well as more pointed wings and a faster wingbeat. However, it is best distinguished by its quite different common call, a nasal two-note call with the second note lower in pitch (however, juvenile and sometimes adult American Crows produce similar calls). Fish Crows may feed on an extraordinary range of foods, including carrion, crustaceans, insects, berries, seeds, nuts, bird eggs, turtle eggs, and human garbage. They generally forage in flocks, mainly by walking, especially along the shore or in very shallow water. They may drop mollusks from the air to break open their shells. In colonies of herons and other waterbirds, if the nesting adults are frightened off their nests, Fish Crows may feast on their eggs. Fish Crows often nest in loose colonies of a few pairs. Courtship may involve the male and female flying close together in a gliding display flight. The nest is placed in an upright fork of a tree or shrub. The nest may be placed very low at coastal sites or quite high in deciduous trees in inland swamps (1 to 21 m above the ground or even higher) The nest (which is probably built by both sexes) is a bulky platform of sticks and strips of bark lined with softer materials such as grass,rootlets, hair, feathers, paper, pine needles, and even manure. The female lays 4 to 5 dull blue-green to gray-green eggs blotched with brown and gray. Incubation is by the female (possibly assisted by the male) for 16 to 18 days. Nestlings are probably fed by both parents. The age at which young leave the nest is uncertain, but is probably around 3 to 4 weeks. (Kaufman 1996; AOU 1998; Dunn and Alderfer 2011)
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Fish crow

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The fish crow (Corvus ossifragus) is a species of crow associated with wetland habitats in the eastern and southeastern United States.

Taxonomy

The fish crow was first described by Alexander Wilson in 1812. The latest genetic testing now seems to indicate this species is closely related to the Sinaloa crow (C. sinaloae) and the Tamaulipas crow (C. imparatus), and not as close to the American crow (C. brachyrhynchos) as outward signs would suggest.[2]

Description

The fish crow is superficially similar to the American crow, but is smaller (36–41 cm in length) and has a silkier, smoother plumage by comparison. The upperparts have a blue or blue-green sheen, while the underparts have a more greenish tint to the black. The eyes are dark brown. The differences are often only really apparent between the two species when seen side by side or when heard calling. The bill is usually somewhat slimmer than the American crow, but is only readily distinguishable if both species are seen together.[3]

Visual differentiation from the American crow is extremely difficult and often inaccurate.[4] Nonetheless, differences apart from size do exist. Fish crows tend to have more slender bills and feet. There may also be a small sharp hook at the end of the upper bill. Fish crows also appear as if they have shorter legs when walking. More dramatically, when calling, fish crows tend to hunch and fluff their throat feathers.

The voice is the most outwardly differing characteristic for this species and other American crow species. The call of the fish crow has been described as a nasal "ark-ark-ark" or a begging "waw-waw". Birders often distinguish the two species (in areas where their range overlaps) with the mnemonic aid "Just ask him if he is an American crow. If he says "no", he is a fish crow." referring to the fact that the most common call of the American crow is a distinct "caw caw", while that of the fish crow is a nasal "nyuh unh".[5]

Distribution and habitat

This species occurs on the eastern seaboard of the United States from Rhode Island south to Key West, and west along the northern coastline of the Gulf of Mexico and follows many river systems inland for quite some distance. Coastal marshes and beaches, rivers, inland lakes and marshes, river banks, and the land immediately surrounding all are frequented.[3]

Behavior

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Fish crow while vocalizing

Diet

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Fish crow eating an egg

Food is taken mainly from the ground or shallow water where the bird hovers and plucks food items out of the water with its feet. The fish crow is omnivorous. It feeds on small crustaceans, such as crabs and shrimps, other invertebrates, stranded fish, and live fish if the situation favors their capture, eggs and nestlings of birds, small reptiles, the fruits of many trees, peanuts, and grains, as well as human scraps where available.[3]

Breeding

The nest is usually built high in a tree and is often accompanied in nearby trees with other nests of the same species forming small, loose colonies. Usually, four or five eggs are laid. Pale blue-green in colour, they bear blotches of olive-brown.[6] Fish crows build a new nest for each breeding attempt.[7] A pair of fish crows were reported to have raised a young blue jay for multiple weeks.[8]

Conservation

This species appears to be somewhat more resistant to West Nile virus than the American crow. Survival rates of up to 45% have been reported for fish crows, compared with near zero for American crows.[9]

References

  1. ^ BirdLife International (2012). "Corvus ossifragus". IUCN Red List of Threatened Species. 2012. Retrieved 26 November 2013.old-form url
  2. ^ Hardy, John William (1990). "THE FISH CROW (CORVUS OSSIFRAGUS) AND ITS MEXICAN RELATIVES: VOCAL CLUES TO EVOLUTIONARY RELATIONSHIPS?" (PDF). Bioacoustic Laboratory and Archives. Archived from the original (PDF) on 19 September 2016. Retrieved 18 September 2016.
  3. ^ a b c Goodwin, p. 92
  4. ^ Cornell Lab of Ornithology, Fish Crow - Physical Characters
  5. ^ Cornell Lab of Ornithology, Fish Crow - Voice
  6. ^ Goodwin, p. 93
  7. ^ "Fish Crow". TheCornellLab. Retrieved 24 May 2021.
  8. ^ "Fish Crow". TheCornellLab. Retrieved 24 May 2021.
  9. ^ "West Nile and Ravens". Rhode Island Department of Environmental Management. Archived from the original on 9 September 2014. Retrieved 28 April 2014.
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Fish crow: Brief Summary

provided by wikipedia EN

The fish crow (Corvus ossifragus) is a species of crow associated with wetland habitats in the eastern and southeastern United States.

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