What Do Herons Eat? Fish, Frogs and Much More

The main food: fish

Fish are the staple for most of the world’s 70-plus heron species. The great blue heron usually takes fish 10–20 cm (4–8 in) long, but it can handle fish up to about 60 cm (24 in). The gray heron (Ardea cinerea) of Europe, Asia and Africa takes everything from tiny fry under 1 cm long to carp around 30 cm (12 in) and eels well over half a meter long.

Which fish a heron eats depends on what is common and easy to catch. In Nova Scotia, one study found that flounder made up almost the entire great blue heron diet. In British Columbia, herons ate mostly sticklebacks, gunnels, sculpins and perch, while California herons took sculpin, bass, perch, flounder and smelt. Herons are not fussy; they take whatever swims within reach.

Beyond fish: frogs, snakes, mammals and birds

Herons are far more varied hunters than their fishy image suggests.

• Amphibians: frogs, toads, salamanders and newts, often caught in spring when they gather to breed. Gray herons have even been seen rinsing newts in water before swallowing them, which may wash off some of their skin toxins.
• Reptiles: small turtles, lizards and snakes. Great blue herons have swallowed water snakes over 1 m (3 ft) long.
• Crustaceans and insects: crayfish, crabs, shrimp, dragonflies, grasshoppers and water beetles.
• Small mammals: voles, mice, rats, shrews, moles, gophers and young rabbits. In one Idaho study, voles made up roughly a quarter to two fifths of the great blue heron diet, and gray herons in Europe catch water voles and rats.
• Birds: ducklings, rails, young terns and other chicks, usually taken in spring and summer.

Small herons have narrower menus. The yellow-crowned night heron, for example, specializes in crabs, and the cattle egret eats mostly grasshoppers and other insects flushed by grazing animals. For a closer look at a typical heron, see the great blue heron profile.

How herons hunt

The best-known heron technique is to stand and wait. A heron stands motionless at the water’s edge or in shallow water, usually less than about 50 cm (20 in) deep, sometimes for many minutes. When a fish or frog moves within range, the bird uncoils its S-shaped neck and strikes in a fraction of a second.

Herons often sway their heads slightly before striking. This helps them judge the true position of a fish under the water, because light bends at the surface (refraction) and makes the prey look as if it is somewhere else.

Herons also hunt actively. They may wade slowly, stir the mud with a foot to flush hidden prey, or walk through wet meadows and fields to catch voles and grasshoppers. Great blue herons have been seen hovering and dipping for fish, plunging from a perch and even landing briefly on deep water.

Most prey is grabbed between the two halves of the bill rather than skewered. Larger fish and eels are carried to shore, beaten or shaken until still, then turned around and swallowed headfirst so that fins and scales slide down easily. Bones, fur and other indigestible parts are coughed up later as pellets.

When do herons feed?

Herons hunt by sight and are most active around dawn and dusk, when fish move into shallow water and light is low. They also feed during the day and, where there is moonlight or artificial light, at night.

Their diet shifts with the seasons. In spring, frogs, newts and young birds are easy to find. In summer, shallow ponds full of small fish are ideal. In winter, when lakes freeze, northern herons switch to open rivers and streams, hunt rodents in fields or migrate south. Read more in Do great blue herons migrate?

During the breeding season adults need far more food. One study found that great blue heron parents ate up to about four times as much while feeding chicks as while incubating eggs. Chicks are fed regurgitated fish and other prey at the nest, which is described in Where do herons nest?

Why herons visit garden ponds

A garden pond with goldfish or koi is, from a heron’s point of view, an easy meal: shallow water, bright fish and nowhere to hide. Herons have excellent eyesight and spot such ponds from the air, often visiting at first light when gardens are quiet.

In Britain, gray herons are a familiar sight in towns, and in North America great blue herons regularly visit suburban ponds and fish farms. However upsetting a lost fish may be, the birds are protected by law: in the UK under the Wildlife and Countryside Act 1981, and in the United States under the Migratory Bird Treaty Act.

Myths and surprising facts

Myth: herons eat only fish. Fish are the main food, but herons are generalist predators. In some places and seasons, rodents or frogs make up a large part of the diet.

Fact: some herons use bait. Green herons, and occasionally gray herons and little egrets, have been seen dropping bread, insects, feathers or twigs onto the water to lure fish within striking distance. It is often cited as a rare example of tool use in birds.

Fact: herons sometimes choke. Because they swallow prey whole, herons now and then try to swallow a fish that is too large and choke on it. This is rare, but it shows how ambitious these hunters can be.