Wood duck
| Wood duck | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
,_Parc_du_Rouge-Clo%C3%AEtre,_Brussels.jpg)
Wood ducks ( Aix sponsa ), ♂ |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Aix sponsa | ||||||||||||
| ( Linnaeus , 1758) |
The Wood Duck ( Aix sponsa ) is a bird art from the family of ducks (Anatidae). Their natural range is North America. It lives near forest lakes and is adapted to life in forest areas. Trees serve as breeding and resting places. It prefers to breed in the abandoned nesting holes of woodpeckers. A few hours after hatching, the chicks jump several meters to the ground in order to follow the female parent bird to the next body of water. Wood ducks are very maneuverable fliers who also skilfully fly through dense trees. Today they are among the most common ducks in North America. At the beginning of the 20th century, their populations had decreased significantly, so that it was feared that this species would become extinct. Numerous protective measures have contributed to the fact that the population of this species has recovered strongly.
The males wear a contrasting dress, the species is therefore often kept as an ornamental fowl. Feral wood ducks live as so-called captive refugees in small populations also free- living in Europe.
Systematics
The wood duck is assigned to the genus Aix together with the East Asian mandarin duck. The two species are the only recent representatives of this genus. In his first scientific description, Carl von Linné classified the wood duck as the actual ducks . Since then, taxonomists have assigned the species to several different genera, including the genus Dendrocygna , which includes species such as the fall and widow whistle geese .
The common classification of the wood duck in the genus Aix was first proposed in 1828 by Friedrich Boie and taken up again in 1858 by Spencer Fullerton Baird in a catalog of bird species for the Smithsonian Institution . For a long time, the genus was placed with eight others in the Cairinini tribe. Today it is assigned to the swimming ducks. However, the subdivision of the Anatinae is judged differently by taxonomists and the genus and species affiliation is in some cases strongly in upheaval due to new morphological findings. This follows the standard work Ducks, Geese and Swans , which was published in 2005 by the ornithologist Janet Kear , who specializes in ducks .
Although wood duck and mandarin duck are two closely related species, they do not make hybrids. The reason for this is probably that the mandarin duck has a different karyotype . It is also unable to reproduce with most other species of ducks.
Appearance
The wood duck is a small species of duck and reaches a body length of 47 to 54 centimeters. The wing length is between 21 and 24 centimeters. The slightly larger males weigh an average of 680 grams, the females 640 grams. The wood duck is thus slightly smaller than a mallard and is roughly the size of the North American cap saw . The size of the wood duck and the North American cap saw is not accidental. Both use tree hollows of the helmet woodpecker . The range of all three species is also largely identical.
One of the noticeable features of the physique is that the wood duck's eye has the largest diameter of all water bird species with an average of 12.3 millimeters. The tail is also unusually long and is only surpassed by the pintail within the swimming duck .
Plumage of the male
The male has a striking and colorful splendor . The neck feathers, shimmering in metallic green and purple, are elongated into a tuft. This is framed by two white colored lines on each side of the head. The upper white colored line begins at the upper base of the beak and runs in a semicircle to the neck. The white color of the chin and throat runs out in a U-shape on the cheeks. The back plumage is dark green-brown. The wings are metallic blue, green and black and have a blue wing mirror . The feathers of the arm wings have a white tip. The tail plumage is glossy dark green. The upper tail feathers occasionally have a golden brown stripe. The front breast is chestnut red and has small, triangular, cream-colored to white spots and is bordered on the sides by a white and a black vertical stripe. The rest of the underside of the body is white. The flanks are golden brown with very fine dark dashes. The beak is reddish on top with a clearly defined black beak nail. The nostrils are in the back third of the beak, very high on the ridge of the beak. The lower beak is dark. The legs are dark yellow to black brown. The eye ring and the iris are conspicuously orange-red.
The males wear their splendor from late summer to early summer of the following year. The full moult begins with the change of small plumage. Two to three weeks later, the rocker spring is released. From September onwards, most of the males will wear their splendid dress again.
During the short time in which the males wear their plain dress, their body plumage resembles that of the females. However, they still have the white color areas on the throat and chin that are characteristic of males. Their eye-catching orange-red color and the color of their beak also remain unchanged. On the basis of these characteristics, they can be clearly distinguished from female wood ducks and cannot be confused with the female mandarin duck.
Plumage of the female
The females have a gray head and small speckled gray-brown breast and flank plumage. During the breeding season, the neck plumage is slightly elongated. The gray-brown back plumage has a slight purple-green sheen. The chin and throat are white. A conspicuous white eye ring runs around the eye, which is pulled back slightly at the end of the eye. The wing color is largely the same as that of the males, but the colors are a little less intense. The arm wings have teardrop-shaped white spots at their end that are slightly larger than those of the males. The tail is bronze brown. The beak has black spots. The legs are a little darker than the male. The iris is dark brown.
Like the males, the females change the small plumage twice a year and the flight and control feathers once a year. The females go through the full moult about a month earlier than the males. Like the males, they are incapable of flight for a short time during the moult. In the case of breeding females, this time coincides with the period in which the chicks are growing. The resting dress of the female bride ducks largely corresponds to that of the breeding season. The neck feathers are a bit shorter during this time and the white around the eyes is a bit smaller.
Chicks and young birds
The headstock and the top of the body of the bridal ducklings are dark olive brown. The face, throat and belly are greyish white. The chicks have a showy rein that runs from the end of the eye to the back of the neck. There are small pale yellowish-brown spots on the wings and rump. The tail is black and diversified. The forehead is dark. The eyes are noticeably large. Both the claws and the stiff tail help the chicks to climb out of their brood cavity.
Young wood ducks are fully feathered from their seventh to ninth week of life. From this point on, they are very similar to the females. After a further three weeks, they begin to change color to their first age-old dress, and they increasingly show the white facial markings that are characteristic of their gender. At the same time, the beak, iris and feet are given the color of adult wood ducks. Young females can be distinguished from the adult bridal duck females by the broadly lined flank feathers and the gray beak.
Possible confusion with other duck species
The females of the wood duck are very similar in their plumage to the females of the mandarin duck. These are, however, more roughly round-spotted on the flanks and have a narrower eye ring than female wood ducks. Female wood ducks are slightly larger than those of the mandarin duck and have a slightly darker plumage overall. Female mandarin ducks lack the purple-green sheen on their back plumage. Their head is rather gray in color, while the wood duck's head looks almost greenish. The tail part of female mandarin ducks is also shorter.
The chicks of the wood duck resemble those of the mandarin duck in their color distribution. However, they are significantly larger. The plumage is also a little duller and paler than that of the mandarin chicks.
voice
Wood ducks are mostly silent ducks. Occasionally a thin, rising jii-ii can be heard from the male . During courtship, the male also gives a chuckling pfits . The female has a very variable vocal repertoire. Among other things, it calls out a tinny-sounding, drawn-up writ that repeats it rhythmically. A drawn out, squeaking uh-iik belongs to the sounds of the female . The female calls the chicks with chuckling cow cow cow sounds. The chicks learn this call before hatching and in the first hour of their life. They are lured out of their nest cavity by the female with these chuckling sounds and asked to jump to the ground. The chicks are constantly making high-pitched, polysyllabic calls. Chicks who feel threatened will call a quick ti-ti-ti-ti . From around the third month of life, they have mastered the repertoire of adult bridal ducks.
One of the instrumental sounds of the wood duck is a whistling flight noise.
distribution
Original distribution area
The focus of the distribution area of the wood duck is limited to the United States of America and Canada . A very small population also breeds in Cuba. Wood ducks are occasionally seen in Mexico during the winter months. However, they are not breeding birds there. The northern limit of distribution are the east of the Great Lakes , Manitoba , New Brunswick and the south of Québec .
For the North American continent, three populations are distinguished. The western population occurs in southern British Columbia , northeast Montana , the Pacific northwest and California . The second population breeds in an area that stretches across the Great Plains east to the Atlantic coast and extends from the southern Canadian provinces east of Alberta to the US states on the Gulf of Mexico. A third population breeds in the high plains of central North America. Breeding birds are found on the Yellowstone River , Missouri , Wyoming High Plains, and Colorado .
Wood ducks are part-migrants who migrate mainly during the night. The northern populations move south in the winter months and then stay south of the 35th parallel north. During this time they also reach the extreme northeast and the southwestern coastal areas of Mexico in small numbers. The wood ducks living in California and south of a line from North Carolina, Tennessee and Arkansas are predominantly resident birds.
Distribution in Europe
The optically attractive wood duck was imported to Europe as early as the 17th century. It belonged, for example, to the ornamental fowl kept at the royal court at Versailles . There were reports of escaped and then feral wood ducks as early as the 19th century. Wood ducks are popular as ornamental fowl because they are hardy and easily reproduce in captivity. As a rule, the ducks' wings are not clipped , so that feral pairs occasionally breed in the open countryside and reproduce for a short time. After 1900, the ornithologist Oskar Heinroth made targeted attempts to settle in the greater Berlin area . In 1909 this free-living population consisted of around 120 adult animals, which however became extinct again by 1930. Such attempts at naturalization of animals that do not belong to the native fauna are viewed critically today, and no self-sustaining wood duck populations have formed in Central Europe to this day. However, experts believe it is possible that the wood duck could establish itself in the near future.
Duration
Little is known about the numbers of wood ducks before and during the 19th century. However, there are numerous indications in reports from the 18th and 19th centuries that bridal ducks occurred in very large numbers. Due to the numerous bodies of water that still had old trees on their banks during this period, it is very likely that wood ducks were found in greater numbers at that time than is the case today. Above all, tree-lined swamps that have been cut down and drained after settlement by European settlers have disappeared. It is estimated that since European settlement, for example, Texas has lost about 75 percent, Michigan 71 percent, Ohio , Indiana , Illinois and Louisiana each about 50 percent of this habitat.
The wood duck had its population low at the beginning of the 20th century. Since then, their numbers have recovered strongly. The reason for the stock recovery is an increase in the beaver population , a partially targeted (re-) settlement and the installation of artificial nesting holes. Wood ducks also benefit from the fact that a sufficiently old forest has grown back along the rivers of the Great Plains. These areas are also populated again by the helmeted woodpecker. This large species of woodpecker creates a new breeding cave every year. The old ones are used by wood ducks and similar cave-breeding birds.
The wood duck is the most common species of duck in North America today that breeds in tree and nest holes. For 2002 the population was estimated at 2.8 million individuals in the east, 665,100 ducks in central and 66,000 in western North America. The population is increasing, especially in eastern North America.
habitat
The breeding habitat of the wood duck are wooded swamps, shallow lakes or ponds and slowly flowing waters. Many of the bodies of water it inhabits are bodies of water that were created as a result of beaver activities. The water bodies it populates have a dense population of deciduous trees or mixed forest. They find optimal breeding conditions in waters with an average depth between 8 and 48 centimeters and a water surface that is largely sheltered from the wind. The water zone and the bank should be densely lined with trees and shrubs, as is often the case in bald cypress forests, for example. The water surface is shaded by the canopy. Where there are no water-tolerant trees, bulrushes , pond rushes and bridal ducks can also offer sufficient protection. In addition to large amounts of carbohydrate-containing food, the habitat must also have sufficient invertebrates, since egg-laying females in particular are dependent on a high proportion of animal food.
Wood ducks are rarely found in the cold waters of the boreal coniferous forest region. They are completely absent on coastal waters. Wood ducks also colonize park areas if they offer sufficiently secluded retreats. They spend a large part of the day erect. In the winter months they can also be found in more open waters and then occasionally use brackish waters .
Wood ducks usually only stay in pairs or in small groups. Only in winter can accumulations be observed, which can be up to 1000 individuals. Such swarms mainly occur when there is a large regional food supply of acorns and hickory nuts. The wood duck's way of life is closely related to the forest and wood ducks are skilful fliers who can fly through the trees. They are rarely seen in the open.
Food and diet
Wood ducks are basically omnivorous birds whose food composition is largely determined by the supply. They eat parts of aquatic plants, seeds , fruits, invertebrates and also use agricultural areas for foraging. Invertebrates play a very important role, especially for egg-laying females and juvenile ducks.
Acorns are of great importance in the diet of wood ducks . They also eat the seeds of bald cypresses , hickories , beeches , peltandra , holly , rushes , water lilies and fruits such as mulberries and grapes. Both cultivated rice and water rice play a major role in some regions of the range.
The chicks eat almost exclusively animal food until they are six weeks old. These include the larvae of mayflies and dragonflies and newly hatched mosquitoes . The food is mostly picked from the surface of the water. Adult wood ducks also eat beetles , spiders , ants , grasshoppers, and crickets and flies . They also occasionally eat small fish .
Wood ducks have no feeding grounds. They look for food all hours of the day. However, foraging is most intense in the early morning and late afternoon hours. They usually eat in small groups and mostly swim for food. The food is usually picked from the surface of the water. Since they have a relatively narrow beak, which also has only a few lamellas, they seldom strain the water. Instead, the food is usually picked from the surface of the water. Occasionally they also found or dive for food. Usually they then pick up acorns or other large seeds from the bottom of the water. The beak is too weak to crush acorns, for example. Usually these are swallowed whole. Plant parts are torn off.
Wood ducks look for food on land especially when the water they inhabit does not offer sufficient food. You then search the shore zone and the adjacent forest areas for beechnuts , acorns, nuts , berries and fruits. In times of scarcity of food they can also be found on agricultural land and eat soybeans , millet and cereals such as oats and maize .
Reproduction
Courtship
Wood ducks are basically monogamous birds, but their pair bond usually only lasts for one reproductive period. The courtship begins six to seven months before the actual breeding season and thus before migrating bridal ducks migrate to their wintering quarters. During this period the first copulations take place , which primarily serve to bond with the couple.
The courtship is initiated by the females, who during this time let their voices be heard more often. Males that are not mated follow these calls and form small, courtship groups near these females. The courtship repertoire of the wood ducks is very extensive. The common courtship gestures include mutual nibbling on the head and neck plumage. The male's courtship gestures include noticeably turning his head, shaking his head, stretching his head, dipping his beak, ritualized cleaning of the wings and straightening the upper body out of the water. These courtship gestures are mostly triggered by the female, who swims slightly sideways and spreads the tail plumage away from the male. If a male reacts to this swimming behavior by turning his head, the pair has usually been formed. Such pair bonds sometimes only exist for a few minutes or hours at the beginning of the courtship period. The pair bonds strengthen in the course of autumn and early winter. During this time, courtship serves to intensify the pair bond. The courtship takes place mainly on the water. Series flights in which several males follow a female do occur, but are relatively rare.
The pair bond between the sexes lasts until the last week of breeding. Compared to other ducks, male wood ducks stay longer than average near the females. They guard the breeding females against predators and, through their constant proximity, also prevent forced copulation with other males before or during the laying time. Also, harassment of the breeding females by other males is largely prevented by their constant proximity in the nest cavity. This reduces the likelihood that females will give up the clutch.
Breeding loyalty
,_Parc_du_Rouge-Clo%C3%AEtre,_Brussels_(6973269405).jpg)
On the basis of ringed wood ducks, studies have shown that female wood ducks prefer to return to the area in which they themselves grew up and / or in which they have already successfully raised young. The investigations on which these findings are based were mainly carried out on wood ducks that brooded in artificial nesting holes. The wood ducks examined even used the nesting holes of the previous year to a high degree. The probability of the females returning to the immediate breeding area decreased if the clutch was lost the year before. Overall, the return rate of male wood ducks is significantly lower than that of females. In two studies carried out at different locations, 9 to 15.8 percent of the males and between 48 and 58 percent of the females returned to the breeding area. The cause of this low male return rate is due to three behaviors. Males who mate with a female in the breeding area return with the female to this area, provided that the pair bond remains intact in the wintering area. Males that remained unmated in the wintering area prefer to return to the area where they grew up themselves. Males, on the other hand, who form pair bonds in the wintering quarters, follow the females in their breeding area.
The nesting hole
Wood ducks are obligatory cave breeders and nest in tree hollows near bodies of water. In the absence of tree hollows, wood ducks are also very willing to accept nesting boxes.
Although many tree species have suitable hollows in the wood duck's habitat, their nesting holes are particularly found in hardwood trees. In the north of its range include silver , red and sugar maple , American elm , slippery elm , Populus tremuloides , Populus grandidentata , Red Ash , Lime , red oak , dark walnut hickory , black walnut and the American Black Willow among the most frequently used nesting trees. In central North America, besides red and sugar maples, the American plane tree , American beech and the dye areas are of great importance as nesting trees. In the south wood ducks breed preferentially in several species of the Tupelo . In addition to the American plane tree and the American black willow , they also use the bald cypress , the American beech, Quercus nigra and the two-tone oak as nesting trees. The nesting holes of wood ducks are often caused by wind breakage, the death of individual branches or lightning strikes. Wood ducks also often use old, abandoned nesting holes of the helmet woodpecker . The importance of this woodpecker species for the population growth of the wood duck is assessed differently in the literature. There are, however, numerous indications that the increase in the helicopter woodpecker population had a positive effect on the wood duck population. Wood ducks compete with a number of other species for nesting holes. These include other bird species such as the Hooded Merganser , the North American imported European Star and Goldeneye , mammals such as raccoons , foxes and flying squirrels , bees and some snake species. Wood ducks benefit from the presence of squirrels in the breeding area, as these tree hollows often expand so that they are large enough for wood ducks.
The nest box is chosen by the female, who is accompanied by the male. The female prefers to choose nesting holes in the immediate vicinity of water and those nine meters and more above the ground. Due to the small number of tree hollows, the nesting holes are on average 7.6 meters high.
Egg laying
The time at which wood ducks start to lay eggs varies depending on the area of distribution. In the south of the distribution area wood ducks breed as early as February, in the north, however, from mid-March to mid-April. In all areas, oviposition ends before the last week of June.
The eggs are laid with a laying interval of 24 hours. The female covers the first laid eggs with the material found at the bottom of the tree cavity. These are mostly rotting wood as well as leaves and grass that were brought into the cave by croissants , for example . By covering them with this material, the eggs are better protected from predators and insulated against temperature fluctuations. As the eggs are laid, down from the breast plumage of the female is increasingly found in the cover material. The eggs are elliptically oval and have a blunt white shell. The eggs measure an average of about 5 × 4 centimeters. A full clutch has an average of 12.2 eggs. If the clutch is lost, there is usually an additional clutch. This is placed in another nest box. The female breeds alone. The incubation period is on average 31 days. The female leaves the clutch twice a day for about an hour and a half. Your weight loss is 0.68 grams per day. Wood ducks usually only raise one clutch per year. In the extreme south of the distribution area it happens that a second brood is also raised. Occasionally, several females lay eggs in a clutch. Presumably this is a result of the competition for suitable nesting holes. Such joint clutches are usually incubated. The breeding success is only insignificantly lower than with clutches that come from only one wood duck. Female bridal ducks sometimes lay eggs in the nesting holes of cap saws and fall whistled geese .
Chicks hatch and rearing
It takes about six hours for a chick to hatch from the egg. The beeping of the hatching chicks has a stimulating effect on the other chicks, so that the hatching process of a clutch is largely synchronized. The chicks, which weigh an average of 25 grams, are helpless for the first two hours of their lives. However, as soon as their downs are dry, they show a very agile behavior and begin to climb around in the nest cavity. They leave the nest cavity at around 24 to 36 hours of age. They follow the calls of the mother, who lures them from the floor in front of the nest box with gurgling, quick cow-cow-cow sounds. The female parent bird calls for a maximum of one hour. The chicks respond immediately to the call and jump straight into the depths without hesitation. Studies with several duck species have shown that chicks of cave-breeding duck species, unlike ground-nesting species, are generally not afraid of such leaps. Only in the course of the first two weeks of life develops the fear of jumping into the deep. When jumping from the entrance of the nesting holes to the ground, the chicks stretch their feet and beat their wing stumps. The ornithologists Frank Bellrose and Daniel Holm have observed chicks that jumped 15 meters in this way without any obvious injuries. Nestlings who fail to get from the bottom of the nesting cavity to the entrance and jump down from there while the mother bird lures them outside will be left behind by it, even if the chick's beeping is audible to the mother bird.
The mother bird then leads her clutch to the next body of water. Only there can the young find suitable food. Depending on the location of the nest box, the distance can be up to 1.6 kilometers. The chicks feed on the remains of the egg yolk during the migration. It is estimated that mallard chicks can be without food for at least 48 hours after hatching. There are no comparable data for bridal ducklings. The loss of chicks during the migration to the next body of water is very high and increases with the length of the path. The mother bird leads the chicks using available cover. Open spaces are crossed at high speed. Approaching predators are tempted by the mother bird . The close bond between mother duck and chick ends very early in comparison to other swimming ducks. From an age of around 35 days, the chicks react only slowly or not at all to the calls of the mother bird. As a rule, the chicks leave the mother bird and not the other way around. Chicks orphaned early do not have a significantly different mortality rate from chicks that are guided, provided they have reached an appropriate body of water.
The chick growth rate is very high. The chicks, which weigh an average of 25 grams when hatched, weigh around 400 grams forty to 45 days later. The young ducks are able to fly when they are around 70 days old. They are fertile in their first year of life.
Causes of mortality
The eggs of the wood duck are eaten by snakes, the American mink , fox, gray squirrel and red squirrel, as well as various woodpeckers such as the golden and red-headed woodpecker . The importance of the individual species as nest predators varies depending on the distribution area. In all areas of distribution, however, the raccoon is an essential nest predator. Chicks hatch from around 62 percent of the clutch. A number of predators hunt the chicks . These include predatory mammals such as foxes and raccoons. Chicks are also eaten by snapping turtles , bullfrogs , largemouth bass , Mississippi alligators , great horned owls , red-shouldered and red-tailed buzzards , Hudson's harriers and night herons . In wood ducks that breed near human settlements, large numbers of chicks are also killed by domestic cats and domestic dogs . Out of a hundred hatched chicks, between 41 and 65 reach the age at which they fledge. Most chicks die in the first two weeks of life.
Of the adult wood ducks, roughly one in two experiences the next year of life. The mortality rate of the males is slightly lower than that of the females. Females are at greater risk from predators during the breeding season. Brooding females are struck by foxes, gray squirrels , raccoons and the pine snake , among others . Another factor contributing to their higher mortality rate, however, is that fierce fighting occurs between egg-laying females when a female tries to lay an egg in the clutch of another female. These fights often result in head injuries that can be severe enough to kill the injured duck. The degree of intraspecific aggression is unusually high for a bird species. Since the proportion of injured and killed brooding ducks depends on the brood density in an area, ornithologists Frank Bellrose and David Holm see this behavior as a stock-regulating mechanism.
Wood duck and human
The indigenous peoples of North America were very familiar with the wood duck. This is indicated, among other things, by numerous finds of pottery with decorations that resemble the head of the wood duck. Only owls can be found more often on these clay works. Replicas of wood ducks can also be found on kalumets , the pipes that played a role in ceremonial acts for some Indian ethnic groups . The Natchez also celebrated a Moon Festival, which included the presentation of shot wood ducks. Findings during excavations on the hills of the Cahokia culture also indicate the importance of the wood duck as a source of food . 45 bones found were verifiably derived from the wood duck. However, other species of duck were of greater importance. 480 bones came from mallards, 199 from teals , 78 from blue-winged ducks, 426 from other duck species and 453 skeletal remains from geese and swans .
The European settlers also noticed the colorful duck very early on and bridal ducks were also brought to Europe very early. Proof of purchase for wood ducks, which were intended for the zoological collection of a French aristocratic family, exists as early as 1663. Many of the early explorers who traveled to the North American continent mention the wood duck in their reports and have made drawings of it. These include John Lawson , Mark Catesby , George Edwards , John James Audubon and John and William Bartram .
The hunt for the wood duck intensified with the improvement of firearms and, together with the change in the habitat of the wood duck through the draining of water and forest clearing, led to a sharp decline in the population. At the beginning of the 20th century, these population declines were so noticeable that it was feared that this species would become extinct. As early as the 1920s, measures were taken in the USA to relocate them in individual regions. Numerous bird chicks that had been hatched in enclosures were poached. Between 1916 and 1941, the hunt for this species of duck was also largely restricted and numerous nesting boxes were installed, which are very heavily used by this species. In the early 1970s the population was 1.3 million birds. The population is still significantly lower than before the colonization of North America began. The duck can, however, be found again today in most of its former range.
supporting documents
Individual evidence
- ↑ Bellrose and Holm, p. 5
- ↑ Janet Kear (Ed.): Ducks, Geese and Swans . Oxford University Press, 2005, ISBN 0-19-854645-9
- ↑ Bellrose and Holm, p. 6
- ↑ a b c d e f g h Kear, p. 462
- ↑ a b Gooders and Boyer, p. 23
- ↑ a b c Bellrose and Holm, p. 3
- ↑ a b c d e Christopher S. Smith: Field Guide to Upland Birds and Waterfowl . Wilderness Adventure Press, Belgrade (Montana) 2000, ISBN 1-885106-20-3 , p. 74
- ↑ a b Gooders and Boyer, p. 24
- ↑ a b c d e Kolbe, p. 177
- ↑ a b c d e f g Kolbe, p. 176
- ↑ Kolbe, p. 178
- ^ A b Hans-Heiner Bergmann, Hans-Wolfgang Helb, Sabine Baumann: The voices of the birds of Europe - 474 bird portrait with 914 calls and chants on 2,200 sonograms . Aula-Verlag, Wiesbaden 2008, ISBN 978-3-89104-710-1 , p. 52
- ↑ Bellrose and Holm, p. 235
- ↑ Bellrose and Holm, p. 1
- ↑ a b Bellrose and Holm, p. 15
- ↑ Bellrose and Holm, p. 27 and p. 28
- ↑ Heinroth, p. 62ff.
- ^ Olaf Geiter, Susanne Homma, Ragnar Kinzelbach: Inventory and evaluation of neozoa in Germany (PDF; 3.3 MB) . Research report by the Institute for Biodiversity Research (Chair for General and Special Zoology) at the University of Rostock on behalf of the Federal Environment Agency, texts 25/02. Berlin 2002, ISSN 0722-186X , p. 82
- ↑ Bellrose and Holm, p. 61
- ↑ Bellrose and Holm, p. 67
- ↑ a b c d e f Kear, p. 463
- ↑ Bellrose and Holm, p. 71
- ↑ Bellrose and Holm, p. 387
- ↑ Bellrose and Holm, p. 387 and p. 388
- ↑ Bellrose and Holm, p. 388
- ↑ Bellrose and Holm, pp. 389 to 391
- ↑ Bellrose and Holm, p. 394
- ↑ a b c Bellrose and Holm, p. 123
- ↑ a b c d e f g h i j Kear, p. 464
- ↑ Bellrose and Holm, p. 127
- ↑ Bellrose and Holm, p. 156
- ↑ Bellrose and Holm, p. 95
- ↑ a b Bellrose and Holm, p. 104
- ↑ Bellrose and Holm, p. 41
- ↑ Bellrose and Holm, p. 167
- ↑ Bellrose and Holm, p. 276
- ↑ Bellrose and Holm, p. 175
- ↑ a b Bellrose and Holm, p. 218
- ↑ a b c d e f Kear, p. 465
- ↑ Bellrose and Holm, p. 234
- ↑ Janet Kear: Man and Wildfowl . T & AD Poyser, London 1990, ISBN 0-85661-055-0 , pp. 137 and 138.
- ↑ Bellrose and Holm, p. 238
- ↑ a b Bellrose and Holm, p. 241
- ↑ Bellrose and Holm, p. 242
- ↑ Bellrose and Hom, pp. 308 and 309
- ↑ Bellrose and Holm, p. 318 and p. 319
- ↑ Bellrose and Holm, p. 325
- ↑ Bellrose and Holm, p. 314
- ↑ Bellrose and Holm, pp. 256 to 262
- ↑ Bellrose and Holm, p. 7
- ↑ a b Bellrose and Holm, p. 8
literature
- Frank C. Bellrose, Daniel J. Holm: Ecology and Management of the Wood Duck. Stackpole Books, Mechanisburg, Pennsylvania 1994, ISBN 0-8117-0605-2 .
- John Gooders, Trevor Boyer: Ducks of Britain and the Northern Hemisphere. Dragon's World Ltd, Surrey 1986, ISBN 1-85028-022-3 .
- Oskar Heinroth: The wood duck, Lampronessa sponsa (L.), and their naturalization on our park waters. J. Neumann Publishing House (Neudamm), 1910.
- Janet Kear (Ed.): Ducks, Geese and Swans. Oxford University Press, 2005, ISBN 0-19-854645-9 .
- Hartmut Kolbe: The world's ducks. Ulmer, Stuttgart (Hohenheim) 1999, ISBN 3-8001-7442-1 .
Web links
- Aix sponsa in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed on December 18 of 2008.
- Videos, photos and sound recordings for Aix sponsa in the Internet Bird Collection