Pygmy snow goose
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Pygmy snow goose ( Anser rossii ) |
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| Anser rossii | ||||||||||||
| Cassin , 1861 |
The pygmy snow goose ( Anser rossii ), also known as the horse's snow goose , is a species of field geese native to North America and thus belongs to the real geese (Anserini). It is sometimes with the snow goose ( Anser caerulescens ), the emperor goose ( Anser canagicus ) and the Bar-headed Goose ( Anser indicus ) in a separate genus with the scientific name Chen asked. She is the smallest of the arctic geese. The species was first described scientifically in 1861 by J. Cassin.
The pygmy snow goose is an extremely rare wanderer in Western Europe. However, it is also possible that most of the birds observed were captive refugees.
Appearance
With a body length of 53 to 66 cm, the pygmy snow goose is about the same size as a brent goose ( Branta bernicla ), its weight is usually between 1.2 kg and 1.6 kg, females are generally somewhat lighter than males. It looks very similar to the snow goose, but is significantly smaller and has a shorter beak than the snow goose . The mostly slightly upright and quite rounded body is covered by pure white plumage; The only exception are the black flight feathers. The neck of the pygmy snow goose is comparatively short; As mentioned, the same applies to the pink beak, which has small bluish protrusions at the base, which are less pronounced in the female. Eye color is dark brown. The legs are colored in strong pink, and the high-standing, clearly visible heel joint is also striking.
Similar to the snow goose , in rare cases there is a dark color morph. These are possibly due to a mating with dark snow geese.
Young animals have a weight of around 65 grams when they hatch, their plumage is initially largely gray, only on the belly side it is a little lighter, occasionally also yellowish. The color of the beak and legs initially looks greyish-green before the color of the adult animal prevails; the flight feathers, on the other hand, are often kept in different shades of brown.
distribution and habitat
Little snow geese are migratory birds that move back and forth between their northern breeding grounds and their wintering areas further south over the course of the seasons. They leave the latter in February, the former in early September.
Geographically, the breeding areas are in northwest Canada , particularly in the Perry River area and on the Siberian Wrangel Island , while the wintering area is more widely distributed. This includes areas of California close to the coast , in particular the Sacramento Valley , but also parts of New Mexico and the highlands of Mexico . The American Gulf Coast of Texas and Louisiana , the marshes of the Mississippi - Delta and even (though rarely) the Atlantic coast are regularly visited by dwarf snow geese. Sometimes individual flocks - often together with barnacle geese - also fly to north-western Europe, especially to Iceland , the Faroe Islands , and more rarely to Belgium , the Netherlands or Germany . Otherwise the pygmy snow goose appears in Central Europe only as a neozoon that has escaped from captivity in breeding stations.
The breeding area is characterized by short summers and a harsh climate in which only tundric grasses and herbs , mosses and lichens , low-growing birches and dwarf willows can grow. The geese live mainly on flat, rocky islands, possibly overgrown with small bushes, which are located in larger lakes and thus do not allow predators to enter. In winter, on the other hand, plateaus, marshes and, today, agricultural land form their habitat.
Diet and Lifestyle
Dwarf snow geese live on the roots , sprouts and seeds of arctic grasses and herbs as well as on green parts of aquatic plants such as sedges ( Carex ). In the winter area, grass seeds and small pieces of roots are also an important part of the diet, and arable land and cattle pastures are also cut.
The extremely social animals usually live in large flocks and are mainly active during the day. Natural enemies, especially for the young, are seagulls and the arctic fox .
Reproduction
The breeding process of the dwarf snow geese is determined by the short and climatically harsh summer of their breeding areas. When the first smaller groups arrive in the last weeks of May or the first of June, there is often still snow. As soon as this has melted, the female starts building the nest ; the male does not take part in this work. The copulation between the partners connected for life had already taken place on the train long before this point in time. The nesting place is mostly small hollows dug into the ground, which are almost always on the leeward side of boulders or small bushes to protect against the cold wind and are covered with small twigs, blades of grass, moss or lichen and finally with down feathers . The individual nests of birds that breed in colonies are often close together.
Depending on the climatic conditions, the female lays two to seven, but mostly four or five pink to creamy, matt-glossy eggs between the beginning and the end of June , which are laid one after the other in a 24-hour cycle. If the first clutch is destroyed, there is no additional clutch. Only the female breeds while the gander guards the females and clutch. About three weeks later (with a fluctuation range of about three days) the young animals hatch at the same time. While they were still grazing in the breeding colony with their families at the beginning, they left the breeding area with their parents three weeks later towards the end of July and went to pastures near the water, where the individual families unite to form larger groups. This is where the moulting begins with the parents , which lasts about a month, so that at the same time as their young, who fledge after five and a half to six and a half weeks, they regain the ability to fly around mid to late August. In the former, the adult plumage develops after almost three months; however, they have already migrated together with their parents to the winter areas, where they arrive in October to November. From the second, sometimes even third year of life, they are themselves ready to reproduce.
The pygmy snow goose not only mates with other species; There are reports of hybrids with the gray goose ( Anser anser ), the snow goose ( Anser caerulescens ), the emperor goose ( Anser canagica ) and the red-necked goose ( Branta ruficollis ).
Danger
Little snow goose are not considered to be threatened. Originally a rather rare species, the number of individuals is increasing significantly. Since the mid-1950s, the population growth has been dramatic in some cases. According to individual estimates, the population growth between the 1950s and 1990s was 10 percent annually. Only a decrease in the number of breeding pairs on Wrangel Island was recorded.
Attitude in Europe
The first snow geese kept in Europe were imported from California at the beginning of the 20th century. However, until the end of World War II, pygmy snow geese remained duck birds, rarely shown by zoos or bred by private individuals. The scientist Peter Markham Scott took part in a research trip to the Arctic Perry River in 1949 , who brought several pygmy snow geese back to Europe from this research trip. The keeper of the geese was the British Wildfowl Trust , which established a breed from which the majority of the pygmy snow geese kept in Europe came. Since the 1980s, the number of animals shown has decreased again. On the one hand, an inbreeding depression contributed to this . At the same time, an increasing number of zoos abandoned the keeping of this species of geese, which are abundant in the wild, and turned to the conservation breeding of the more threatened red-necked and brent goose .
Individual references, literature and web links
literature
- Jonathan Alderfer (Ed.): Complete Birds of North America , National Geographic, Washington DC 2006, ISBN 0-7922-4175-4
- Erich Rutschke: Wild geese, way of life - protection - use , Berlin: Parey, 1997
- H. Kolbe, Die Entenvögel der Welt, 5th edition, Ulmer Eugen Verlag (1999) ISBN 3-8001-7442-1
- Richard Sale: A Complete Guide to Arctic Wildlife. Christopher Helm, London 2006, ISBN 0-7136-7039-8 .
Web links
- Videos, photos and sound recordings about Anser rossii in the Internet Bird Collection
- Anser rossii inthe IUCN 2013 Red List of Threatened Species . Listed by: BirdLife International, 2012. Retrieved November 30, 2013.
Individual evidence
- ↑ Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.): The compendium of birds in Central Europe: Everything about biology, endangerment and protection. Volume 1: Nonpasseriformes - non-sparrow birds , Aula-Verlag Wiebelsheim, Wiesbaden 2005, ISBN 3-89104-647-2 , p. 59
- ^ Sales, p. 95
- ↑ Alderfer, p. 7
- ↑ Kolbe, p. 116