Red Knot

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Red Knot
winter plumage
winter plumage
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Scolopacidae
Genus: Calidris
Species: C. canutus
Binomial name
Calidris canutus
(Linnaeus, 1758)
Distribution and migration routes of the six subspecies of the Red Knot
Distribution and migration routes of the six subspecies of the Red Knot
Synonyms

Tringa canutus

The Red Knot, Calidris canutus (just Knot in Europe), is a medium sized shorebird which breeds in tundra and the Arctic Cordillera in the far north of Canada, Europe, and Russia.

Birds bred in north America migrate to coastal areas in Europe and South America, while birds bred in Europe migrate to Africa, Papua New Guinea, Australia and New Zealand (see distribution map). This species forms enormous flocks in winter.

Contents

[edit] Taxonomy

This species was first described by Linnaeus in his Systema naturae in 1758 as Tringa canutus.[2] It is sometimes said that the Red Knot gets its name from King Cnut, but there is no factual basis for this story. A more likely etymology is that the name is onomatopoeic, based on the bird's grunting call note.

There are six subspecies, in order of size;

  • C. c. roselaari (largest)
  • C. c. rufa
  • C. c. canutus
  • C. c. islandica
  • C. c. rogersi
  • C. c. piersmai (smallest)

[edit] Behaviour

The Red Knot nests on the ground, near water, and usually inland. The female lays 3 to 4 eggs in a shallow scrape lined with leaves and moss. Both parents incubate the eggs, but the female leaves before the young fledge. After the young have fledged the male begins his migration south and the young make their first migration on their own.

On the breeding grounds, Knots eat mostly spiders, arthropods, and larvae obtained by surface pecking, and on the wintering grounds they eat a variety of hard-shelled prey such as bivalves, gastropods and small crabs that are ingested whole and crushed by a muscular stomach.

[edit] Description

An adult Red Knot is 23-26 cm long with a 47-53 cm wingspan. It has short dark legs and a medium thin dark bill. The body is mottled grey on top with a cinnamon face, throat and breast and light-coloured rear belly. In winter the plumage becomes uniformly pale grey. canutus, islandica and piersmai are the “darker” subspecies. rogersi has a lighter belly than either roselaari or piersmai, and rufa is the lightest in overall plumage.

The weight varies with subspecies, but is between 100 and 200 g. Red Knots can double their weight prior to migration.7676786

[edit] Status

The Red Knot has an extensive range, estimated at 0.1–1.0 million square kilometres (0.04–0.38 million square miles), and a large population of about 1.1 million individuals. The species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e., declining more than 30% in ten years or three generations), and is therefore evaluated as Least Concern.[1]

C. c. canutus and C. c. islandica are among the subspecies to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

[edit] Threats to the American subspecies (C. c. rufa)

[citation needed]

Near the end of the 19th century, large numbers of Knot were shot for food during migration in North America. More recently, the birds have become threatened as a result of extensive commercial harvesting of horseshoe crabs in Delaware Bay which began in the early 1990s. Delaware Bay is a critical stopover point during spring migration; the birds refuel by eating the eggs laid by these crabs, and with reduced numbers of horseshoe crabs living in the bay there are fewer eggs to feed on.

In 2003, scientists projected that at their current rate of decline the American subspecies might go extinct as early as 2010. Several environmental groups have petitioned the U.S. government to list the birds as endangered, but thus far their requests have been denied. In New Jersey, state and local agencies are taking steps to protect these birds by limiting horseshoe crab harvesting and restricting beach access. In Delaware, a two-year ban on the harvesting of horseshoe crabs was enacted but struck down by a judge who cited insufficient evidence that the ban would help restore the Red Knot's numbers to justify the potential disruption to the fishing industry.

[edit] References

  1. ^ a b {BirdLife International (2004). Calidris canutus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006. Database entry includes justification for why this species is of least concern
  2. ^ (Latin) Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.. Holmiae. (Laurentii Salvii)., 149. “T. roftro laevi, pedibus cinerascentibus, remigibus primoribus ferratis.” 
  • Shorebirds by Hayman, Marchant and Prater ISBN 0-395-60237-8
  • Baker, Allan J., et al. 2004 Rapid Population Decline in Red Knots: Fitness Consequences of Decreased Refueling Rates and Late Arrival in Delaware Bay, Proceedings of The Royal Society 271, 875-882.
  • Piersma, T., de Goeij, T. P. & Tulp, I. 1993 An evaluation of intertidal feeding habitats from a shorebird perspective: towards relevant comparisons between temperate and tropical mudflats. Netherlands Journal of Sea Research 31, 503-512.
  • Piersma, T., Dietz, M. W., Dekinga, A., Nebel, S., van Gils, J. A., Battley, P. F. & Spaans, B. 1999 Reversible size-changes in stomachs of shorebirds: when, to what extent, and why? Acta Ornithologia 34, 175-181.
  • Tomkovich, P. S. 1992 An analysis of the geographic variability in knots Calidris canutus based on museum skins. Wader Study Group Bulletin 64 Supplement, 17-23.
  • Tomkovich, P. S. 2001 A new subspecies of Red Knot Calidris canutus from the New Siberian Islands. Bulletin of the British Ornithologists Club 121, 257-263.
  • Tulp, I., Schekkerman, H., Piersma, T., Jukema, J., de Goeij, P. & van de Kam, J. 1998 Breeding waders at Cape Sterlegova, northern Taimyr, in 1994. Zeist: WIWO - Report 61.

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