Heron - WikiHQ

Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus Botaurus are referred to as bitterns, and, together with the zigzag heron, or zigzag bittern, in the monotypic genus Zebrilus, form a monophyletic group within the Ardeidae. Egrets do not form a biologically distinct group from herons, and tend to be named differently because they are mainly white or have decorative plumes in breeding plumage. Herons, by evolutionary adaptation, have long beaks.

The classification of the individual heron/egret species is fraught with difficulty, and no clear consensus exists about the correct placement of many species into either of the two major genera, Ardea and Egretta. Similarly, the relationships of the genera in the family are not completely resolved. However, one species formerly considered to constitute a separate monotypic family, the Cochlearidae or the boat-billed heron, is now regarded as a member of the Ardeidae.

Although herons resemble birds in some other families, such as the storks, ibises, spoonbills, and cranes, they differ from these in flying with their necks retracted, not outstretched. They are also one of the bird groups that have powder down. Some members of this group nest colonially in trees, while others, notably the bitterns, use reed beds.

Name

The word heron first appeared in the English language around 1300, originating from Old French hairon, eron (12th century), earlier hairo (11th century), from Frankish haigiro or from Proto-Germanic *haigrô, *hraigrô.

Herons are also known as shitepokes ( ), or euphemistically as shikepokes or shypokes. Webster's Dictionary suggests that herons were given this name because of their habit of defecating when flushed.

The 1971 Compact Edition of the Oxford English Dictionary describes the use of shitepoke for the small green heron of North America (Butorides virescens) as originating in the United States, citing a published example from 1853. The OED also observes that shiterow or shederow are terms used for herons, and also applied as derogatory terms meaning a thin, weakly person. This name for a heron is found in a list of game birds in a royal decree of James VI (1566–1625) of Scotland. The OED speculates that shiterow is a corruption of shiteheron.

Another former name was heronshaw or hernshaw, derived from the Old French heronçeau. Corrupted to handsaw, this name appears in Shakespeare's Hamlet. A possible further corruption took place in the Norfolk Broads, where the heron is often referred to as a harnser.

A group of herons has been called a "siege".

thumb|The [[goliath heron is the largest heron species.]]

Description

thumb|left|[[Yellow bittern with its neck fully retracted.|alt=A beige heron with yellow legs and bill stands hunched on a wire mesh above water, its neck folded tightly to its body and hidden among feathers.]]

The herons are medium- to large-sized birds with long legs and necks. They exhibit very little sexual dimorphism in size. The smallest species is usually considered the dwarf bittern, which measures in length, although all the species in the genus Ixobrychus are small and many broadly overlap in size. The largest species of heron is the goliath heron, which stands up to tall.

thumb|X-ray of the cervical vertebrae in the neck of an unidentified heron

All herons can retract their necks by folding them into a tight S-shape, due to the modified shape of the cervical vertebrae, of which they have 20 or 21; the neck is retracted during flight, unlike most other long-necked birds. The neck is longer in the day herons than the night herons and bitterns. The legs are long and strong, and in almost every species are unfeathered from the lower part of the tibia (the exception is the zigzag heron). In flight, the legs and feet are generally held in a horizontal position, pointing backwards. Toes are long and thin, with three pointing forwards and one backwards.

thumb|The [[Pacific reef heron has two colour morphs, the light and the dark.|alt=two herons, one with white plumage and one with slate grey, on a rock in the surf of the ocean]]

alt=A close-up of white heron with a droplet of water on its beak.|thumb|A white heron with a droplet of water on its beak in Forest Park.

The bill is generally long and harpoon-like. It can vary from extremely narrow, as in the agami heron, to wider as in the grey heron. The most atypical heron bill is owned by the boat-billed heron, which has a broad, thick bill. Herons' bills and other bare parts of the body are usually yellow, black, or brown, although this can vary during the breeding season. The wings are broad and long, exhibiting 10 or 11 primary feathers (the boat-billed heron has only nine), 15–20 secondaries, and 12 rectrices (10 in the bitterns). The feathers of the herons are soft and the plumage is usually blue, black, brown, grey, or white, and can often be strikingly complex. Amongst the day herons, little sexual dimorphism in plumage is seen (except in the pond herons); however, for the night herons and smaller bitterns, plumage differences between the sexes are the rule. Many species also have different colour morphs.

Distribution and habitat

thumb|alt=Lava heron, grey with a long bill and red feet and with small fish in bill amongst grey rocks|[[Lava herons are endemic to the Galápagos Islands, where they feed on fish and crabs in the intertidal and mangrove areas.]]

The herons are a widespread family with a cosmopolitan distribution. They exist on all continents except Antarctica and are present in most habitats except the coldest extremes of the Arctic, extremely high mountains, and the driest deserts. Almost all species are associated with water; they are essentially non-swimming waterbirds that feed on the margins of lakes, rivers, swamps, ponds, and the sea. They are predominantly found in lowland areas, although some species live in alpine areas, and the majority of species occur in the tropics. Many species also opportunistically take larger prey, including birds and bird eggs, rodents, and more rarely carrion. Even more rarely, herons eating acorns, peas, and grains have been reported, but most vegetable matter consumed is accidental. The wings may be used to frighten prey (or possibly attract it to shade) or to reduce glare; the most extreme example of this is exhibited by the black heron, which forms a full canopy with its wings over its body.

Some species of heron, such as the little egret and grey heron, have been documented using bait to lure prey to within striking distance. Herons may use items already in place, or actively add items to the water to attract fish such as the banded killifish. Items used may be man-made, such as bread; alternatively, striated herons in the Amazon have been watched repeatedly dropping seeds, insects, flowers, and leaves into the water to catch fish.

Three species, the black-headed heron, whistling heron, and especially the two cattle egret species, are less tied to watery environments and may feed far away from water. Cattle egrets improve their foraging success by following large grazing animals, and catching insects flushed by their movement. One study found that the success rate of prey capture increased 3.6 times over solitary foraging.

Breeding

thumb|The larger bitterns, like this [[American bittern, are solitary breeders. To advertise for mates, males use loud, characteristic calls, referred to as booming.|alt=A brown heron with brown, back, and beige coloured streaks stands in similarly coloured dead grasses, its head pointed upwards]]

While the family exhibits a range of breeding strategies, overall, the herons are monogamous and mostly colonial. Most day herons and night herons are colonial, or partly colonial depending on circumstances, whereas the bitterns and tiger herons are mostly solitary nesters. Colonies may contain several species, as well as other species of waterbirds. In a study of little egrets and cattle egrets in India, the majority of the colonies surveyed contained both species. Nesting is seasonal in temperate species; in tropical species, it may be seasonal (often coinciding with the rainy season) or year-round. Even in year-round breeders, nesting intensity varies throughout the year. Tropical herons typically have only one breeding season per year, unlike some other tropical birds which may raise up to three broods a year. In colonial species, displays involve visual cues, which can include adopting postures or ritual displays, whereas in solitary species, auditory cues, such as the deep booming of the bitterns, are important. The exception to this is the boat-billed heron, which pairs up away from the nesting site. Having paired, they continue to build the nest in almost all species, although in the little bittern and least bittern, only the male works on the nest.

Generally, herons lay between three and seven eggs. Larger clutches are reported in the smaller bitterns and more rarely some of the larger day herons, and single-egg clutches are reported for some of the tiger herons. Clutch size varies by latitude within species, with individuals in temperate climates laying more eggs than tropical ones. On the whole, the eggs are glossy blue or white, with the exception being the large bitterns, which lay olive-brown eggs. In response to these findings, the International Ornithological Congress  reclassified Ardeidae and their sister taxa Threskiornithidae under the order Pelecaniformes instead of the previous order of Ciconiiformes.

The cladogram shown below is based on a molecular phylogenetic study of the Ardeidae by Jack Hruska and collaborators published in 2023. For several species these results conflict with the taxonomy published online in July 2023 by Frank Gill, Pamela Rasmussen and David Donsker on behalf of the International Ornithological Committee (IOC). in Zagreb Zoological Garden, Croatia

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References

External links

HeronConservation Heron Specialist Group of IUCN
Heron videos on the Internet Bird Collection