Herons
Have you ever hiked along the edge of a quiet stream or marsh and startled a big, long-legged bird that flapped slowly out of the water, leaving only a widening ripple? Chances are good that the bird was a heron.
There are about 60 species of herons distributed throughout most of the world, except in the extreme northern and southern regions. Herons are most common in the tropics. Herons, bitterns and egrets are closely related, belonging to the family Ardeidae of the order Pelecaniformes. The term “heron” is used sometimes to embrace the family group. Other close avian relatives include ibises and spoonbills. Herons are wading birds with long, slender legs, long necks and long, heavy bills tapering to a sharp point. Their wings are broad and rounded, their tails short. Most herons, especially the larger ones, are graceful in form and movement.
Herons are predators, feeding on animal life (fish, frogs, crayfish, snakes, insects, invertebrates and small rodents) found in shallow water and along the shoreline. Herons swallow food whole and later regurgitate pellets of indigestible matter. They inhabit both freshwater and saltwater areas. In Pennsylvania, they are found on lakes, reservoirs, ponds, rivers, wooded streams, bogs, marshes and swamps, where they typically stand at the water’s edge or walk slowly through the shallows. Herons sometimes forage in open, grassy fields and meadows. They may also perch in trees near or over water
Herons are shy birds. When approached by humans, they usually take off in slow flight, with head and neck drawn back in an S-shape and legs held straight to the rear. Most herons are strong fliers, propelling themselves with deep, pumping wing strokes.
Certain adaptations help a heron wade about and catch prey in shallow water. The most obvious is its legs, which elevate the bird above the water’s surface. The toes are long and flexible for walking or standing on soft ground. The bill is sharp-tipped, and is used mostly for grasping, but is sometimes used to impale prey. The long, muscular neck delivers a lightning-quick blow, with plenty of force to penetrate the water and seize a fish.
Herons have well-developed “powder down,” areas of feathers with tips that continually disintegrate into powder. Preening helps distribute this powder, which absorbs and removes fish oil, scum and slime, thus keeping the rest of the plumage clean and dry. Herons preen with a serrated middle claw.
Males are aggressive and defend small territories in breeding season. They fight (although rarely causing physical damage); sound harsh calls; go through elaborate, instinctive motions such as raising their wings, stretching their necks, fluffing their feathers, or erecting their crests. Some also put on spectacular flight routines. In most species, during breeding season the plumage color becomes richer and bright colors appear on the bill, legs or in the bare skin around the eyes.
Often the male begins building a nest to attract a mate; then the female takes over construction and the male brings sticks and twigs. Mated herons defend a zone immediately around their nest against intrusion of other birds. Some species nest in colonies (sometimes called heron rookeries), while others are solitary nesters. Herons may nest in mixed colonies (great blue, black – and yellow-crowned night-herons building nests in the same grove of trees). Or, in certain parts of their range, they may nest with cormorants, pelicans and ibises.
After breeding, three to six unmarked bluish, greenish, or brownish eggs are laid in a nest of sticks in a tree (herons and egrets) or a nest of grasses on the ground (bitterns). The eggs are incubated by both parents for 2 1/2 to 4 weeks, depending on the species. Some herons begin incubating immediately after the first egg is laid, so that young hatch at intervals and differ in size.
At first, parents regurgitate pre-digested liquid food to their nestlings. Later, they bring partly digested food, and finally whole fish, frogs, snakes and other items. A growing heron or bittern will grasp the base of its parent’s bill in a scissors-grip and wrestle with it. This triggers an impulse in the adult either to drop or regurgitate the food.
The following herons and allies, which breed in Pennsylvania, are covered in this Wildlife Note: American bittern, least bittern, great blue heron, great egret, green heron, black-crowned night-heron, yellow-crowned night-heron. For more detailed information about these listed species, please see the agency’s endangered species web page. All of these herons are migratory, generally breeding in northern areas and migrating south in autumn. Some species migrate in flocks, some in small bands, and some individually.
Wading birds are part of the complex web of life in the marshes and along the water’s edge. Their presence is an expression of the health of the watersheds and wetlands they inhabit. When several species of herons inhabit a waterway, lake or swamp, specialized feeding patterns often differentiate these species. The great blue heron usually wades in deeper water, looking for small fish. Great egrets hunt the shallow water often closer to shore. The green heron waits motionless for its prey near a log or bank. Bitterns snatch frogs and tadpoles among the reeds. On dry ground, egrets forage for grasshoppers and other insects stirred up by livestock, while the black – and yellow-crowned night herons patrol shallow waters in the late evening and at night.
Although mainly predators, herons are also prey for some species, including foxes, minks, hawks and especially raccoons. Crows, hawks, and tree-climbing snakes may rob unguarded nests. Few predators dare tackle an adult heron, especially one of the larger species that have a big awl-like bill that can inflict great damage with lightning-fast quickness.
At one time herons were killed for their plumage, which was used to decorate women’s hats and other clothing. Today, habitat loss is the primary human-influenced threat to herons, especially loss of wetland, riparian and coastal habitats. Degraded and acidic rivers also negatively affect heron populations. All migratory birds are protected under the federal Migratory Bird Treaty Act of 1918.
Herons, and many other species of wildlife, benefit from Pennsylvania Game Commission waterfowl projects and habitat preservation and enhancement work on State Game Lands. Wildlife Management Areas such as Pymatuning, Middle Creek and Shohola Lake (SGL 180) provide many acres of excellent marsh and habitat. Propagation areas within these waterfowl management areas restrict public access which provides greater protection to waterfowl, herons and other wildlife, especially during the breeding season. These protected spaces are critical to many bird species, particularly endangered species and species of conservation concern, which are most sensitive during nesting, brooding and raising young. Also, the Game Commission owns and manages some of the largest wetlands in the state which are critical nesting and foraging areas for herons and other birds that require that habitat. Several of these wetlands and larger heron colonies have been selected as state Important Bird Areas. Heron nesting colonies are especially important to protect because they concentrate a population into a small area. Herons literally put all their eggs in one basket, so it is important to protect each “basket.” Therefore, heron colonies are protected through the Natural Heritage Program and the Environmental Review process. These colonies are monitored through the Game Commission’s colonial waterbird program. The American bittern, least bittern, and great egret are considered endangered in the state due to their rarity and the vulnerability of their colonies.
