Heron

• 1. Introduction

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  The heron stands in shallow water, perfectly still, for minutes at a time. Then its head tilts, tracks, and the bill strikes with the speed of a thrown spear. This family of birds, the Ardeidae, counts 75 recognised species, spread across every continent except Antarctica. Some of those species you may know as egrets or bitterns, but biologically they belong to the same family. What makes a heron a heron? What separates it from the cranes and storks it resembles? And why has the English language given this bird so many strange and colourful names? Those questions drive this documentary.

• 2. A Name With Deep Roots

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  Around 1300, the word heron first entered written English. It travelled through Old French, appearing as hairon and eron in the 12th century and hairo in the 11th, tracing back further to the Frankish haigiro and to the reconstructed Proto-Germanic root haigrô or hraigrô. That is an unusually traceable etymology for a common bird name.

  Webster's Dictionary records another name entirely: shitepoke, pronounced to rhyme with "white spoke." The name refers, bluntly, to the bird's habit of defecating when startled. The 1971 Compact Edition of the Oxford English Dictionary traces this term in North American use, applied specifically to the small green heron of North America, Butorides virescens, with a published example from 1853. The OED also documents politer corruptions: shikepoke and shypokes.

  A related term, shiterow or shederow, appears in a royal decree of James VI of Scotland, who lived from 1566 to 1625. There the word appeared in a list of game birds, already carrying a secondary life as a derogatory term for a thin, weakly person. The OED speculates that shiterow is a corruption of shiteheron.

  Heronshaw and hernshaw were once common alternatives, derived from the Old French heronçeau. One corruption of that word, handsaw, found its way into Shakespeare's Hamlet. In the Norfolk Broads, the local name became harnser. A gathering of herons, meanwhile, carries a collective noun that sounds more suited to a military operation: a siege.

• 3. Form Built for the Hunt

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  The goliath heron stands up to 152 centimetres tall, making it the largest member of the family. At the opposite end, the dwarf bittern is generally considered the smallest, though several species in the genus Ixobrychus overlap closely in size. Between those extremes, the family shows very little sexual dimorphism in body size.

  The neck is the most mechanically remarkable feature. Herons have 20 or 21 cervical vertebrae, modified in shape so the neck can fold into a tight S-curve. During flight, that neck pulls back against the body. This is the visible characteristic that separates herons from the storks, ibises, spoonbills, and cranes they superficially resemble: those birds fly with necks outstretched.

  The bill varies across the family. In the agami heron it is extremely narrow; in the grey heron it is wider. The boat-billed heron owns the most atypical bill in the family, a broad, thick structure unlike any other member of Ardeidae. The wings carry 10 or 11 primary feathers in most species, while the boat-billed heron has only nine. Bitterns carry 10 tail feathers where most herons have 12.

  Plumage runs to blues, blacks, browns, greys, and whites, and can be strikingly complex. Day herons show little difference between the sexes in colouring, with the pond herons as the exception. Night herons and smaller bitterns, by contrast, show consistent differences between males and females. The Pacific reef heron offers the most dramatic example of colour variation: both dark and light morphs exist within the species, and the white morph appears only in areas with coral beaches, with the proportion of each morph changing by geography. Herons also carry powder down, a feature shared with only a small number of other bird groups.

• 4. Patience and Strategy

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  The most common hunting method requires almost no movement at all. A heron stations itself at the water's edge, or stands in the shallows, and waits. When prey appears, it tilts its head from side to side to calculate the prey's position in the water and to compensate for the refraction that distorts where underwater objects appear to be. Then the bill strikes.

  A heron that chooses a crouched posture stays more hidden and gets the bill closer to the strike point. One that stands upright gains a wider field of view. Some birds walk slowly through the water, at around 60 paces a minute or fewer, snatching prey when spotted. Others use foot stirring and probing, using their feet to flush hidden animals out of hiding. Wings can be spread to startle prey or, possibly, to draw it into shade.

  The black heron takes wing use to an extreme. It forms a complete canopy with its wings over its body, creating a small patch of shadow. Whether this frightens fish or attracts them to shelter is not fully resolved.

  Some herons use bait. The little egret and grey heron have both been documented placing items in the water to lure fish. Striated herons in the Amazon have been observed dropping seeds, insects, flowers, and leaves into the water repeatedly, then catching the fish that investigate. Man-made items, including bread, have been recorded as bait. Fish drawn this way include the banded killifish.

  The yellow-crowned night heron specialises in crustaceans, particularly crabs. Cattle egrets take a different approach altogether: they follow large grazing animals and catch the insects those animals flush from the ground. One study found that foraging alongside large grazers increased the cattle egret's prey capture success rate by 3.6 times compared with foraging alone.

• 5. Nesting and Reproduction

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  Males at colonial nesting sites arrive before females and begin constructing the nest. They perform a stretch display to attract females, erecting neck feathers and sometimes swelling the neck area. A female approaching too early risks an aggressive response and may need to wait as long as four days before the male accepts her.

  Bitterns and tiger herons diverge from this pattern. Most of them nest alone rather than in colonies, and rely on sound rather than visual displays. The deep booming of the bitterns carries over long distances and functions as the primary courtship signal. The boat-billed heron is the one exception to colonial display norms; it pairs up away from the nesting site entirely.

  Once paired, both birds continue building the nest, with one exception: in the little bittern and least bittern, only the male does the nest construction. Nests are placed in trees where possible, often at considerable height. Species in reed beds nest close to the ground. Colonies are not restricted to remote wetlands; they regularly form in cities when human disturbance is low.

  Clutch sizes run from three to seven eggs in most species. Smaller bitterns sometimes lay larger clutches, and some tiger herons lay only a single egg. Temperate-zone birds lay more eggs than their tropical counterparts within the same species. The eggs are typically glossy blue or white; the large bitterns are the exception, laying olive-brown eggs. Tropical herons generally raise one brood per year, compared to some other tropical birds that can raise up to three.

• 6. Reclassifying a Family

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  For a long time, researchers divided the Ardeidae into two groups based on skull analyses: one diurnal, one covering crepuscular and nocturnal species including the bitterns. DNA evidence and studies of body and limb bones overturned that picture. The skull similarities that had driven the two-group model turned out to reflect convergent evolution, not shared ancestry. Herons in different lineages independently evolved similar skull structures to handle the different challenges of hunting in daylight and hunting at night.

  The current view identifies three major groupings: tiger herons and the boat-billed heron; bitterns; and the day herons, egrets, and night herons together. Whether the night herons deserve their own subfamily, the traditional Nycticoracinae, remains unresolved. The placement of several genera, including Butorides and Syrigma, is still uncertain. The classification is explicitly provisional.

  A 2008 study placed the whole family within the order Pelecaniformes. The International Ornithological Congress responded by reclassifying the Ardeidae, along with their sister group the Threskiornithidae, moving them from Ciconiiformes into Pelecaniformes.

  A molecular phylogenetic study by Jack Hruska and collaborators, published in 2023, added further detail and some conflict. Their results placed the least bittern and the stripe-backed bittern within the genus Botaurus rather than Ixobrychus. They resurrected the genus Calherodius Peters, 1931, to hold two night herons previously placed in Gorsachius: the white-backed night heron and the white-eared night heron. Their data also embedded the western cattle egret within the genus Ardea. As of August 2024, the International Ornithological Congress lists 75 living heron species across 18 genera, with the fossil record extending the family back to at least the Early Miocene.