Little Egret ( Egretta garzetta )
|Leach , 1820
The herons (Ardeidae) are a family in the order Pelecaniformes . There are 62 species in this family . Most species have long legs and a dagger-like beak. Many species also have long necks. Herons are almost exclusively bound to freshwater habitats, the food consists mainly of fish and other water-dwelling animals and is sought there in the shallow water near the shore. They are common worldwide.
All herons have long, dagger-like bills, short tails, and large, broad wings. The neck is bent into an S-shape, which is due to the elongated sixth cervical vertebra. The curved neck is particularly noticeable in flying herons. The so-called day herons are usually large birds with pronounced long necks and long legs; the night herons and tommers are stocky and much shorter-necked. The largest species, the Goliath heron, is up to 140 cm long and has a wingspan of up to 230 cm. The smallest herons are found in the genus of the bittern, some of which only reach a body length of 27 cm. There is little difference in size between males and females: males are around 2 to 4% larger than females. Otherwise there is no conspicuous sexual dimorphism , an exception, however, are the bittern , in which the plumage of males and females is fundamentally different in color. Furthermore, there are often youthful clothes that are very different from the plumage of adult birds.
There are both very colorful and inconspicuous gray-brown herons. The most common colors are black, brown, blue, gray, and white. Often colors serve as camouflage. This is most noticeable with the bitterns , which, with their black-brown stripes, can hardly be seen in the reed beds ; but also apparently strikingly colored herons often have a black and white dashed belly side, which is difficult to see when viewed under water. Many types of day and night herons are characterized by elongated decorative feathers on the head, neck, chest and / or back. These are often conspicuously colored and reach their highest expression in courtship . Another specialty of the heron plumage is the powder down . These down feathers grow for a lifetime and ultimately break down into a powdery substance that is used to cleanse the plumage. Herons usually have three paired plumage regions with powder down, some species have two or four. Herons also have a preening gland , which is very small compared to that of many other waterfowl.
The featherless body parts of the herons are mostly yellow, black or brown. These are the legs and the beak, but also parts of the head between the eye and the beak. These colors become lighter and brighter during the breeding season. The gray heron usually has a yellow-brown beak that turns bright orange-yellow during the breeding season.
The heron's beak is long and dagger-like. The only exception is the boat's beak, which has a very broad, thick beak, a clear deviation from all other species.
The long legs end in an anisodactyl foot. The middle toe is always the longest, the back toe is directly opposite it. The middle toe and inner toe are connected by a basal webbing , otherwise webs are missing. The legs enable walking in deep water. Some species have very elongated toes with which they can get hold of floating parts of plants. The tommels can finally climb around in the bushes and reeds.
The wings have ten to eleven (nine in the Kahnschnabel) hand wings and 15 to 20 arm wings . They allow a slow flight with powerful wing beats. Night herons and tommers flap their wings faster than day herons. The largest herons need 100 wing beats per minute, the smallest 200. The neck is bent backwards in flight so that the head rests on the shoulders. The only exception is the whistling heron , which is also different with its rather duck-like, fast flight.
distribution and habitat
Herons are common on all continents except Antarctica. They are only absent in the polar regions and on some oceanic islands. The greatest biodiversity is found in South and Southeast Asia (24 species), followed by Africa (21), South and Central America (20) and Australia and Oceania (16). The Nearctic with 12 and the Palearctic with 9 species are poorer in species.
Herons are usually residents of the banks of water. They are found mainly on shallow lakes and in swamps, but also on rivers, mangroves and even on the coast of the sea. But there are also exceptions to this rule. Some species are temporarily or permanently found far from the water. The East Asian wavy heron also occurs at the edges of water. Its preferred habitat, however, are subtropical rainforests, where it hunts frogs and earthworms on the forest floor. The best-known example of a heron species that is not bound to water is the cattle egret , which lives in grasslands and savannahs and has no significant connection to water.
Most herons are standing or line birds . However, there are also many distinct migratory birds in the family. The migration behavior of species in the temperate and cold zones is more pronounced than that of species in the tropics. The European populations of the purple heron , night heron and bittern overwinter in sub-Saharan Africa. The gray heron is a partial puller ; 25 to 45% from Central Europe move to the African winter quarters, from Sweden 70%; however, the gray herons are resident birds in the British Isles.
Way of life
The terms day and night heron are not always aptly chosen. There is almost no species of heron that is exclusively diurnal or nocturnal. The gray heron is mostly diurnal, but occasionally also hunts at night without any difference in efficiency being noticed. The night heron is actually mostly crepuscular and nocturnal, but can sometimes also be found hunting in broad daylight. With the African white-backed heron , only one species is known that actually seems to be exclusively nocturnal.
While the day and night herons live in colonies, tiger herons and tommers are loners. The former breed and rest sociable, but usually hunt alone. Especially the solitary bitterns avoid being seen with immobility and colored camouflage ; They have perfected these properties through their post position when threatened, in which they stretch their head and beak up in order to attract even less attention in the reed beds; they can maintain this position for hours.
With a few exceptions, herons feed on aquatic animals, namely fish, amphibians, reptiles, water birds, small mammals, insects, molluscs and crustaceans. The food requirement of a gray heron is at least 330 to 500 g per day. Usually the prey is surprised by the heron standing motionless on the spot and then thrusting its beak at lightning speed. Ideally, the animal to be captured is pierced. Sometimes herons also stride slowly around looking for prey.
Other hunting techniques are less common. A catch of aquatic animals from flight, insect hunting in flight and swimming stalking have been observed in various species.
Many herons use their wings to catch prey. They spread them out to provide shade in which potential prey animals seek supposed protection from the sun. Another benefit of wing shadow is that it minimizes reflections from the water surface and gives the heron better visibility. Many species of heron use this technique occasionally, but the African bell heron almost exclusively. It can form a closed canopy with its wings . Another notable hunting technique is the mangrove heron , which deliberately places insects on the surface of the water as bait to attract fish.
The great herons are able to hunt very large prey. A gray heron has been spotted catching a coot in Belgium ; another was photographed in the Netherlands in Vianen in the province of Utrecht while capturing a rabbit. However, these are exceptions. Looting of bird nests is more common: Little bitterns occasionally eat eggs and young of reed warblers , while the night herons attract the clutches of ibises , terns and other herons.
Some species have an unusual range of prey. White-cheeked herons and black-necked herons have been seen eating carrion, and mangrove herons have even been seen eating acorns. The generalist among the herons is the cattle egret . Although it also occasionally preyes on heron-typical food such as fish and other aquatic animals, it usually stays far away from the water, so that insects have become its main prey. As a cultural follower , he sometimes looks for his food in rubbish dumps, and he also takes large amounts of vegetable food, which he also steals from silos. The cattle egret is particularly known for accompanying large mammals (cattle, buffalo, elephants, etc.) and for freeing them from skin parasites .
Most herons breed in colonies - but there are also solitary species such as the goliath heron and bittern, as well as species that can breed both in colonies and individually, such as the gray heron. Heron colonies can take on enormous proportions: in the Niger Delta , one heron colony comprised 68,300 to 70,800 pairs of different species.
The male first arrives at the nesting site and immediately begins courtship. A series of ritualized gestures are designed to grab a female's attention and keep male competitors away. Such gestures include the vertical stretching of the head and neck, the spreading of the wings, the swinging up and down of the head while raising the feathers and the rattling of bills.
The nests are either in trees or in reeds. In the little bittern, the nest is built exclusively by the male, in other species by both partners together. It is an unstructured accumulation of twigs or reeds. The nests of many species are enlarged every year, which means that they can reach enormous dimensions - around 1.5 m for the gray heron's tree nest. The heron clutch consists of one to ten eggs. The lower extreme (an egg) occurs in the black heron and the white-headed heron, the upper in the miniature tommers. In the vast majority of species, three to five eggs are laid. On average, the herons of the temperate zones have larger clutches than those of the tropics. The eggs are usually glossy white or light blue, with some species also olive brown (bittern) or spotted (tiger heron). They are incubated for 14 to 30 days, which is usually done by both partners. Brood parasitism is also rare , with a female heron laying the eggs in the nest of another species.
The young do not hatch at the same time. The oldest young in a clutch thus has a growth advantage; when it is fed by the parent birds, it tries to force the younger siblings away from the food. As a result, it often happens that the youngest siblings starve to death, or die from aggression with beak blows.
The boys are initially almost completely naked. They remain in the nest for three and a half to thirteen weeks. During this time they are fed with a half-digested food pulp, which is either choked out by both adult birds into the nest or directly into the boy's beak.
Although heron fossil finds are extremely rare, they show that herons are a very ancient group of birds: the genus Proardea from the Eocene of France is the oldest known heron, and footprints are known from the same period, probably from herons. The lines of the large day heron and the small night heron can already be recognized in the Miocene , some of which are already assigned to the recent genera Ardea , Ardeola , Egretta and Nycticorax .
In the Pleistocene many of the extant species already living. Ardea bennuides , a heron widespread on the Arabian Peninsula and the largest known species that has ever lived, did not become extinct until a very young age .
In total, fewer than forty fossil species have been described. Furthermore, an extinct family Xenerodiopidae is known from the Oligocene, which is believed to be close relatives of the herons.
For a long time, the herons were assigned to the walking birds , where they were grouped with storks , ibises and New World vultures, among other things . One of the few exceptions was that of Ligon, who in 1967 separated the herons from the wading birds (Ciconiiformes) in a separate order Ardeiformes; in the latter he combined storks and New World vultures. The relationship of the herons to the other families of the walking birds remained unexplained for a long time.
Recent genetic analyzes suggest that the herons, like their sister clade the ibises and spoonbills , belong to the Pelecaniformes, i.e. are more closely related to the pelicans than to the storks. This classification, which is also used in this article, is also followed by the International Ornithological Union (IOU).
Carl von Linné assigned all of the herons known to him to a single genus Ardea . In the 20th century it became customary to divide the family into the subfamilies of the real herons (Ardeinae) and the tommers (Botaurinae). Payne and Risley, however, distinguished four lines in 1976: the great day heron (Ardeinae), the small night heron (Nycticoracinae), the tiger heron (Tigrisomatinae) and the tiger heron (Botaurinae) - a system that has often been quoted and adopted.
In contrast, in 2005, Kushlan and Hancock put the day and night herons back together in a common subfamily. They also separate the different boat-billed and the Agami Heron on as their own subfamilies Agamiinae and Cochleariinae. The separation of the spear heron was made here for the first time, while the boat's beak had long been viewed as a strongly deviating species, and occasionally even its affiliation to the herons was doubted.
The following classification of the herons follows Kushlan & Hancock 2005:
- Subfamily day heron (Ardeinae)
- Tribus Ardeini
- Genus Ardea
- Gray Heron , Ardea cinerea
- Great blue heron , Ardea herodias
- Cocoi Heron , Ardea cocoi
- White-necked Heron , Ardea pacifica
- Great Egret , Ardea alba
- Middle heron , Ardea intermedia
- Black-necked heron , Ardea melanocephala
- Madagascar Heron , Ardea humbloti
- Imperial heron , Ardea insignis
- Sooty Heron , Ardea sumatrana
- Goliath Heron , Ardea goliath
- Purple Heron , Ardea purpurea
- Genus Bubulcus
- Cattle Egret , Bubulcus ibis
- Genus Butorides
- Genus Schopfreiher , Ardeola
- Genus Ardea
- Tribus Egrettini
- Genus Egretta
- Red Egret , Egretta rufescens
- Pied Heron , Egretta picata
- Brown-throated heron , Egretta vinaceigula
- Bell heron , Egretta ardesiaca
- Three-colored heron , Egretta tricolor
- White-cheeked Heron , Egretta novaehollandiae
- Blue Heron , Egretta caerulea
- Great Egret , Egretta thula
- Little Egret , Egretta garzetta
- Middle heron , Egretta intermedia
- Snow heron , Egretta eulophotes
- Reef Freer , Egretta sacra
- Coastal Heron , Egretta gularis
- Genus Syrigma
- Whistling heron , Syrigma sibilatrix
- Genus Pilherodius
- Capped heron , Pilherodius pileatus
- Genus Nyctanassa
- Genus Egretta
- Night heron tribe, Nycticoracini
- Tribus Ardeini
- Subfamily Dommeln , Botaurinae
- Genus bittern , botaurus
- Genus bittern , Ixobrychus
- Striped bobbin , Ixobrychus involucris
- American bittern , Ixobrychus exilis
- Little bittern , Ixobrychus minutus
- Chinadommel , Ixobrychus sinensis
- Von schrenck's bittern , Ixobrychus eurhythmus
- Cinnamon bobble , Ixobrychus cinnamomeus
- Gray-backed bobbin , Ixobrychus sturmii
- Black bittern , Ixobrychus flavicollis
- † Black-backed little bittern , Ixobrychus novaezelandiae
- Genus Zebrilus
- Zigzag Heron , Zebrilus undulatus
- Subfamily Tiger Heron , Tigrisomatinae
- Subfamily Agamiinae
- Spear Heron , Agamia agami
- Subfamily Cochleariinae
- Kahnschnabel , Cochlearius cochlearius
Herons and humans
Herons have probably been hunted for millennia. For example, evidence of heron hunting from the second millennium BC has been found in Mexico. In the Middle Ages, herons in Europe belonged to the so-called high hunt, which was reserved for the nobility. The heron hunting was in De arte venandi cum avibus , the Falk book of Friedrich II. Described and illustrated. There was even a "Heron War" between the Baron of Crailsheim and the Margrave of Ansbach, in which there was a dispute over the possession of a gray heron colony. The gray heron was not only hunted for pleasure, but was also considered a particularly exquisite food.
Heron hunting experienced the greatest expansion with the increasing popularity of heron feathers. For many peoples, the ornamental feathers of various types of heron were important as jewelry - for example with the Maori , for whom the feathers of the great egret were common as headdresses of the chiefs, or with Indian peoples who used the feathers of the white heron as barter goods. At the end of the 19th century it became fashionable in Europe to adorn hats with the feathers of white herons (especially great egrets and little egrets). For this purpose, an unprecedented hunt began worldwide, in which entire colonies were destroyed, including the species that breed with herons. The dimensions of this hunt are illustrated by a few examples: in 1887 a single dealer in London offered two million herons hides; In 1898, 1.5 million herons were exported from Venezuela . The destruction of the heron colonies was the motivation for the establishment of the first conservation organizations, above all the National Audubon Society of the USA - two men appointed by the Audubon Society to protect a heron colony were even killed by hunters. In 1913 the USA banned the trade in heron feathers, Great Britain followed in 1920. To this day the great egret is the heraldic animal of the Audubon Society.
While hunting for meat and feathers only plays a very subordinate role today, herons are seen primarily as competitors to the fishing industry . Extermination campaigns by fishermen have been documented since the 19th century. Studies have shown that herons almost exclusively eat fish that are uninteresting for fishing, but in Europe and North America there are repeated demands from fishermen's associations to decimate the heron populations.
The relationship between humans and cattle egrets, which mainly eats insects, is mostly positive. Since it remains close to humans, it was seen as a useful tool for combating locust plagues. This is how it was introduced in Hawaii, for example.
Threat and protection
Herons are sensitive to changes in their habitat near the water. The clearing of bank vegetation, the straightening of rivers, the pollution of the water, the overfishing of the lakes and the sprawl of their habitats are reasons for the decline of many heron species.
The IUCN lists four species of heron as extinct:
- the Rodrigues night heron ( Nycticorax megacephalus ), which lived on Rodrigues until the 18th century ; known from bone finds and two descriptions from 1708 and 1726
- the Mauritius Night Heron ( Nycticorax mauritianus ), known from fossil bones, probably from the 17th century to Mauritius existent
- the Réunion night heron ( Nycticorax duboisi ), widespread on Réunion until the 17th century , a bone find known
- the New Zealand bittern ( Ixobrychus novaezelandiae ), native to the South Island of New Zealand and extinct before 1900
Whether the great heron Ardea bennuides of the Middle East was exterminated by humans falls within the realm of speculation. He still lived 3000 BC. BC and was thus contemporary of the first civilizations of that region.
None of the heron species living today are threatened with extinction. However, the IUCN lists six species in the endangered status (Great White Heron, Red-headed Heron, Imperial Heron, Madagascar Heron, Great-billed Heron, Australian Bittern).
Herons in art
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- Kushlan et al., P. 284 and p. 285
- Telegraph.co.uk (September 29, 2008): Heron catches rabbit: Dramatic photos
- Milagros Gonzalez-Martin, Xavier Ruiz: Brood Parasitism in Herons . In: Colonial Waterbirds 1996, Vol. 19, No. 1, pp. 31-38
- E. Hoch: Reflections on Prehistoric Life at Umm an-Nar (Trucial Oman) Based on Faunal Remains from the Third Millennium BC In: South Asian Archeology 1979, pp. 589-638
- JD Ligon: Relationships of the cathartid vultures . In: Occasional Papers of the Museum of Zoology, University of Michigan 1967, No. 651, pp. 1-26
- Frederick H. Sheldon & Beth Slikas : Advances in Ciconiiform Systematics 1976-1996 . In: Colonial Waterbirds 1997, Vol. 20, No. 1, pp. 106-114
- Hackett et al: A Phylogenomic Study of Birds Reveals Their Evolutionary History. In: Science. June 27, 2008: Vol. 320. no. 5884, pp. 1763–1768 doi : 10.1126 / science.1157704
- List of bird names in the IOU IOC World Bird List
- RB Payne & CJ Risley: Systematics and evolutionary relationships among the herons . In: Miscellaneous Publications, Museum of Zoology, University of Michigan 1976, No. 150, pp. 1-115
- FH Sheldon, KG McCracken & KD Stuebing: Phylogenetic relationships of the Zigzag Heron (Zebrilus undulatus) and White-crested Bittern (Tigrionis leucolophus) estimated by DNA-DNA hybridization . In: The Auk 1995, No. 112, pp. 672-679
- David W. Steadman, Markus P. Tellkamp & Thomas A. Wake: Prehistoric Exploitation of Birds on the Pacific Coast of Chiapas, Mexico . Condor 2003, Vol. 105, No. 3, pp. 572-579
- see also under falconers
- H. Kramer: The herons . In: Bernhard Grzimek (Ed.): Grzimeks Tierleben - Vögel 1 . dtv 1980, pp. 179-206
- Nycticorax megacephalus in the endangered Red List species the IUCN 2011. Posted by: BirdLife International, 2008. Accessed November 17, 2011th
- Nycticorax mauritianus in the endangered Red List species the IUCN 2011. Posted by: BirdLife International, 2008. Accessed November 17, 2011th
- Nycticorax duboisi in the endangered Red List species the IUCN 2011. Posted by: BirdLife International, 2008. Accessed November 17, 2011th
- Ixobrychus novaezelandiae in the Red List of Threatened Species of the IUCN 2011. Posted by: BirdLife International, 2008. Accessed November 17, 2011th
- Josep del Hoyo et al .: Handbook of the Birds of the World , Volume 1 ( Ostrich to Ducks ). Lynx Edicions, 1992, ISBN 84-87334-10-5
- James A. Kushlan & James A. Hancock: Herons . Oxford University Press, 2005, ISBN 0-19-854981-4