Gray heron
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Gray heron ( ardea cinerea ) |
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| Linnaeus , 1758 |
The Gray heron ( Ardea cinerea ), and heron called, is a bird art from the order Pelecaniformes . It is widespread and common in Eurasia and Africa. Four subspecies are distinguished worldwide. In Central Europe it is represented with the nominate form Ardea cinerea cinerea .
Appearance
The gray heron reaches a body length of 90 to 98 centimeters and usually weighs between 1 and 2 kilograms. Well-fed birds can weigh more than 2 kilograms, emaciated specimens only weigh up to 810 g. The wingspan is between 175 and 195 centimeters. There is no noticeable gender dimorphism . The males, however, are on average slightly larger. It is like with this look very the North American Great Blue Heron , which occupies there a similar ecological niche as the European Gray Heron.
The plumage of the gray heron is white on the forehead and skull, gray-white on the neck and ash-gray on the back with white bands. It has black eye stripes and three long black feathers that form a plume , a triple row of black spots on the front neck and black wings. The long beak is yellowish and turns brown on the ridge of the beak. The wax skin is yellow and turns greenish towards the eye. Individual individuals can, however, deviate significantly from the plumage typical of the gray heron and have a different distribution pattern. The three long front toes are spread wide apart on the stilt leg and prevent sinking into the soft ground. The beak type is the tweezer beak.
The gray heron only has a very stunted rump gland . Instead, he has powder feathers on his chest and in the groin, which he occasionally rubs his head against and crumbles it. The resulting powder is very fatty and is distributed over the body to protect it from moisture. The powder downs constantly grow back and do not fall out during the moult.
The departure is often initiated with a few jumps. Gray herons fly with slow wing beats, their heads retracted to the shoulders and an S-shaped neck. Only during take-off and landing is the neck stretched out. A loud, harsh cheek can be heard regularly during the flight . When walking fast, a balancing neck movement can be observed. While foraging for food, they usually walk slowly with their necks stretched out.
distribution
The gray heron is found in the milder and southern regions of Europe and Asia, and in all of southern Africa with the exception of the southern coasts of Namib . It is absent within this large distribution area only in the tundras, deserts, steppes and high mountains. In Central Europe it is a very common breeding bird. The highest population densities are achieved in lowland areas with a lot of water. In Switzerland, the highest breeding grounds are found at altitudes of 900 to 1,230 meters, in Germany it occurs at altitudes between 800 and 1060 meters.
Depending on the distribution area, the gray heron is a short-range migrant , partial migrant or resident bird . The British and Irish breeding birds are mostly resident birds, but a wintering in Israel and Senegal has also been proven for individual birds. The other European gray herons usually migrate in a south-south-westerly direction during the winter months. From Poland a south-south-east migration direction dominates. However, only the breeding areas in northern Europe and those at high altitudes are completely abandoned by gray herons. One of the longest proven train routes to date is the train of a Swedish gray heron, which was found in Sierra Leone and covered a distance of 5,865 kilometers. The migration to the wintering quarters starts in September and they return from the end of February to the beginning of March.
Young birds show a post-breeding season migration from September. They pull in all directions, with a southwest pulling direction slightly dominating. The distances they cover can be several 100 kilometers.
habitat
Gray herons are habitat generalists who are equally at home in freshwater inland, at estuaries and in coastal regions. Their demands on their living space are relatively low. They need to be close to waters with shallow water zones, relatively large prey, and four to five months in which the waters do not freeze over. Accordingly, they can be found on lake shores, rivers, flood zones, reed belts, swamps, ponds, beaches, mangroves and salt marshes. Pastures that are some distance from the nearest body of water are also used. The heron usually finds such habitats in the lowlands. But it also shows a height distribution that is unusual for herons. In Armenia, for example, it occurs at altitudes of 2,000 meters above sea level and in north-western India it is found at altitudes of 4,000 meters. He very often uses bodies of water that were created by man. These include backwater, rice fields and fish ponds. As resting and nesting trees, he uses tall trees that are as free as possible from disturbances.
In recent times it has been making its way into urban areas, where it can often be seen even in the city centers. It also forms common groups with the Little Egrets , for example in the Po Valley in northern Italy.
Duration
Current inventory
The gray heron is the most widespread species of heron in Eurasia. In Europe, the breeding population was between 210,000 and 290,000 breeding pairs at the beginning of the 21st century. With a few exceptions, the gray heron population increased in the 20th century. It has also increased its range in Europe. In many European countries, a decrease in the hunting of the species has contributed to the population increase. In France, for example, the number of breeding pairs rose from 4,500 to 27,000 between 1974 and 1994 after the species was placed under protection there. The same applies to Germany, where there are large colonies with more than a hundred breeding pairs, especially in northern Germany. The German breeding population was estimated at 24,000 to 27,500 breeding pairs towards the end of the 20th century. The largest European colony with 1,000 to 1,900 breeding pairs can be found in Brittany.
In West Africa the number of breeding pairs is very small and may be less than 500 pairs outside of Mauritania . The Mauritanian population, which breeds in isolation on the coast, is significantly larger. The number of breeding pairs in 1997 was 4,188 breeding pairs. In contrast, the gray heron is a widespread species in East Africa. In Tanzania alone there are over 15,000 specimens. The populations are also increasing in southern Africa, as the species here primarily benefits from the reservoirs.
Inventory development in Central Europe
Some of the large Central European breeding colonies of the gray heron had already declined in the last third of the 19th century. The population continued to decline until 1940, although some countries such as Switzerland placed them under protection at an early stage. The war- related cessation of hunting led to a short-term recovery in the first half of the 1940s. After that, populations declined dramatically by the late 1960s. Many colonies were given up and at the same time a reduction in the distribution area could be observed. Only through the restriction or prohibition of persecution did the population increase in the 1970s. Supported by favorable climatic conditions, the population continues to increase in certain areas, which has led to an expansion of the area and the establishment of new colonies. The increase is only interrupted by cold winters. In the meantime, it has been shown in some areas that the capacity limit has been reached.
Way of life
Foraging
The gray heron usually looks for food alone. Only where there is an abundant supply of food can they be seen in loose, small schools and occasionally also with other species. If they eat solitary, then they are able to vigorously defend their food territory. Such intraspecific aggression occasionally even leads to the killing of a competing heron. The level of aggression varies depending on the season and is highest when gray herons raise young birds. The preferred feeding grounds can be in the immediate vicinity of the nesting site, but are occasionally at a considerable distance from it.
As calm as a bittern, the gray heron stalks long-legged through the shallow water with bowed head and crooked neck. It stings at lightning speed for smaller fish, frogs, newts, snakes and aquatic insects. It also eats rats and water voles , which it - like the other food animals - devours whole. In meadows, it waits rigidly for field mice and occasionally eats eggs and young birds. Typical for such high-seat hunts is first a slow leaning forward and then a quick thrust. To hunt fish, it can land on the water, swim for one to three seconds and then fly up again. The preferred method, however, is to land a few feet from the water and then slowly step into the water.
Breeding behavior
As a rule, gray herons do not reach sexual maturity until they are two years old. They are monogamous, bigamy or polygyny is very rare .
The nest is a large, not very stable structure made of sticks in tree tops. In Central Europe, the nests are usually built high on deciduous or coniferous trees. Nesting places in the reeds, however, are very rare. Both parent birds are involved in nest building. Usually the male enters the nesting material. Old nests are very often reoccupied. The appearance of the incomplete construction of the nest is attributed to the fact that the heron only brooded on the ground not so long ago. Evidence for this is given that in Holland, for example, colonies of herons can be found in large reeds.
The clutch consists of four to five eggs, the laying interval is usually two days. The eggs are oval, light blue-green and without a gloss. The incubation period is between 25 and 26 days. The young birds hatch asynchronously. Both parents are involved in feeding the nestlings. The nestlings are hovered up to the 14th day of life, the young birds are only left alone from the 20th day. At around 30 days they are able to climb onto other branches on the breeding tree, and at around 50 days they are able to fly. However, they usually return to the nest for another ten to twenty days.
The mortality of the young herons is very high during the nesting period. It is estimated that 70% of the young die in the first six months. The oldest known ringed gray heron reached an age of 35 years and one month.
Social behavior
Heron colonies are very lively. There is constant quarrel between the birds in a colony, as the birds dispute among each other for nesting material. Together, the birds fend off the crows that are interested in the unguarded eggs.
Hunting and defense against damage in Germany
The gray heron is game within the meaning of the Federal Hunting Act. A hunting season was only set in Bavaria (September 16 - October 31), according to the regulation on the abolition of the closed season for gray herons of July 25, 1983 (colloquial: gray heron regulation) within a radius of 200 meters around closed waters ( within the meaning of Art. 2 Para. 1 Nos. 1 and 2 of the Fisheries Act). In the other federal states, the gray heron was spared all year round, which means that an individual permit from the Lower Hunting Authority is required for a kill (so-called scare-off kills). There are now special regulations to protect pond farms in Schleswig-Holstein, in Thuringia since 2012 and in Saxony since 2013. In Schleswig-Holstein between 100 and 200 birds are shot every year, which has been criticized by the Naturschutzbund Deutschland , since the Schleswig-Holstein population decreased by around 60 percent from around 2,700 breeding pairs to around 1,100 breeding pairs between 2002 and 2014.
In North Rhine-Westphalia , the gray heron is no longer included in the list of huntable species since the introduction of the so-called “Ecological Hunting Act NRW” on May 28, 2015, contrary to the regulations of the Federal Hunting Act.
On smaller ponds, spanning with nets has proven itself to prevent damage. At larger ponds, gray herons can be kept away with wires stretched along the edge of the bank (prevents them from stepping from the bank into the water). Scarecrows are usually quickly recognized as harmless and therefore only offer short-term protection.
In most cases, no significant damage to the fishing industry can be observed in natural waters, as the heron only looks for food in shallow water and there usually only catches economically insignificant fish species.
See also
literature
- 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 .
- James A. Kushlan, James A. Hancock: Herons . Oxford University Press, 2005, ISBN 0-19-854981-4
Web links
- Photo series on the behavior of gray herons in the wild
- Ardea cinerea in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 2 of 2009.
- Videos, photos and sound recordings of Ardea cinerea in the Internet Bird Collection
- Age and gender characteristics (PDF; 5.6 MB) by J. Blasco-Zumeta and G.-M. Heinze (Eng.)
- Feathers of the gray heron
Individual evidence
- ↑ Kushlan et al., P. 70
- ↑ Urs N. Glutz von Blotzheim , KM Bauer: Handbuch der Vögel Mitteleuropas . Volume 1: Gaviiformes - Phoenicopteriformes, AULA-Verlag, Wiesbaden 1993/2001 (first edition 1966), ISBN 3-923527-00-4 , p. 302
- ↑ a b c d e Bauer et al., P. 263
- ↑ a b Kushlan et al., P. 74
- ↑ a b c Kushlan et al., P. 73
- ↑ Bauer et al., P. 264
- ↑ a b c Bauer et al., P. 265
- ↑ Bauer et al., P. 263 and p. 264
- ↑ Closed season restriction for gray herons , accessed on July 31, 2017
- ↑ Shooting of gray herons , accessed on July 31, 2017
- ↑ NABU : No protection for cormorants and gray herons , April 2015, accessed on July 31, 2017
- ^ Ministry of the Interior and Local Affairs of the State of North Rhine-Westphalia, Section 56: Laws and Ordinances | State law NRW. Retrieved March 6, 2017 .