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Nov 12 2011

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Shelduck (Tadorna tadorna)

Shelduck

[order] ANSERIFORMES | [family] Anatidae | [latin] Tadorna tadorna | [authority] Linnaeus, 1758 | [UK] Shelduck | [FR] Tadorne de Belon | [DE] Brandgans | [ES] Tarro Blanco | [NL] Bergeend

Subspecies

Monotypic species

Genus

The shelducks, genus Tadorna, are a group of large birds in the Tadorninae subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans. The namesake genus of the Tadorninae, Tadorna is very close to the Egyptian Goose and its extinct relatives from the Madagascar region, Alopochen. While the classical shelducks form a group that is obviously monophyletic, the interrelationships of these, the aberrant Common and especially Raja Shelducks, and the Egyptian Goose were found to be poorly resolved. Fossil bones from Dorkovo (Bulgaria) described as Balcanas pliocaenica may actually belong to this genus. They have even been proposed to be referable to the Common Shelduck, but their Early Pliocene age makes this rather unlikely.

Physical charateristics

The common shelduck is not sexually dimorphic, meaning males and females look alike. The only distinguishing characteristic is that males have a “knob” between their bill and forehead during the summer. These large ducks have white plumage, with dark green coloration on the head and random spots on the back. They also have brown coloration under the tail and in a band across the chest. Outside of the breeding season and as juveniles, these colors will appear somewhat duller. They also have pink legs and a red bill.

Listen to the sound of Shelduck

[audio:http://www.planetofbirds.com/MASTER/ANSERIFORMES/Anatidae/sounds/Shelduck.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 100 cm wingspan max.: 120 cm
size min.: 55 cm size max.: 65 cm
incubation min.: 29 days incubation max.: 31 days
fledging min.: 33 days fledging max.: 31 days
broods: 1   eggs min.: 8  
      eggs max.: 10  

Range

Eurasia, Africa : widespread

Habitat

These birds can be found on temperate coasts and wetlands in Europe, Africa, and Asia. They nest in western Europe through the Middle East and Central Asia into northeast China, while spending their winters south of this region through North Africa.

Reproduction

These ducks are very social and tend to live in large flocks, some containing up to 50 birds. These birds are monogamous, so when a mating pair is formed, they stay together for life. They build nests in caves, deserted burrows, and other similar places. Females will lay their eggs in May and lay as many as twelve eggs in a clutch, which can take up to one month to hatch. Both parents help care for the young, which are able to fly six to eight weeks after hatching. Shortly thereafter, they will leave the nest.

Feeding habits

Common shelducks will feed on a variety of small invertebrates, including insects and crustaceans.

Video Shelduck

httpv://www.youtube.com/watch?v=x5nDxKjjQ9Y

copyright: youtube


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Tadorna tadorna is a widespread breeder in coastal areas of north-west and southeast
Europe, which accounts for less than half of its global breeding range. Its
European breeding population is relatively small (<65,000 pairs), but increased moderately between 1970-1990. Although there were declines in Sweden and the United Kingdom during 1990-2000, other sizeable populations-notably in Germany, Netherlands and Russia-were stable or increased, and the species was stable overall.
Shelduck status Least Concern

Migration

British population mainly resident, but with regular, short, seasonal movements, deserting small breeding pools and meres to winter on some large reservoirs. Flocks develop September-December and disperse March-April. Increasing records in continental Europe show that some birds wander further afield. Migratory in North America, withdrawing from breeding range (except in California) to winter in Pacific, Atlantic and Gulf coastal states of USA and south into Mexico, Belize, and Guatemala

Distribution map

Shelduck distribution range map

Literature

Title Aktivitatsrhythmus von Brandgansen (Tadorna tadorna) und Watvogeln (Charadrii) an der Nordseekiiste
Author(s): Hermann Hotker
Abstract: Shelducks, Oystercatchers, Grey Plovers, Knots, Du..[more]..
Source: J. Orn. 136: 105-126.

download full text (pdf)

Title Timing of moult in male and female Shelducks Tadorna tadorna: Effects of androgens and mates
Author(s): Duettmann H., Dieleman S. & Groothuis T.G.
Abstract: We investigated effects of testosterone treatment ..[more]..
Source: ARDEA 87 (1): 33-39

download full text (pdf)

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