Green herons are carnivorous, mainly eating fish and invertebrates. They are opportunistic foragers with a broad prey base, depending on the availability of species present. They exploit superabundant food resources, such as breeding frogs. Their invertebrate diet includes: leeches, earthworms, dragonflies, damselflies, waterbugs, grasshoppers, and crayfish. Some of the many fish eaten are: minnows, sunfish, catfish, perch, eels, and, in urban areas, goldfish. Other vertebrates eaten are rodents, lizards, frogs, tadpoles, and snakes.
Their heavy bill enables them to capture large prey. Feeding can take place at any time, day or night. Typically, prey is captured with a darting stroke of the head and neck, lunging the body towards the victim and either grabbing or impaling the prey.
Among North American diurnal herons, green herons exhibit the fewest kinds of feeding behaviors. They are known to use 15 of the 36 heron feeding behaviors. The most common feeding technique is to stand in a crouched position, horizontal to the water surface, with neck and head retracted. They stand still for long periods of time before changing sites. Standing is often interspersed with slow walking in a crouched posture in the water or bordering vegetation. Herons use their feet to cause potential prey to move and then capture them. They may also dive from perches head first into deep water, becoming submerged, although this isn't a very efficient method. The greatest capture success is in shallowest water (0-10 cm) and the poorest success is in deeper water (20-30 cm).
Green herons are one of the few tool-using birds. They use a variety of baits and lures, such as crusts of bread, mayflies, and feathers. They then put the bait on the water surface and wait for prey to attack the bait. They stand motionless near the bait until a small fish or other animal approaches and then grab the prey. Success rates have been highest when live bait was used versus inanimate or dead bait. Juvenile herons are not as adept at baiting prey (Davis and Kushlan, 1994; Hancock and Kushlan, 1984; Hancock, 1999).
Animal Foods: mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; terrestrial worms; aquatic or marine worms
Primary Diet: carnivore (Piscivore , Insectivore , Eats non-insect arthropods)
Snakes, crows, and common grackles are known to eat green heron eggs. Raccoons eat nestlings. Adult birds may be preyed on by large birds of prey. Green herons remain vigilant to protect themselves from predators. They also utter warning calls when predators approach.
Known Predators:
Anti-predator Adaptations: cryptic
Green herons are small and stocky, with legs that are relatively short, compared to other herons. Body length ranges from 41 to 46 cm. Adults have a glossy greenish-black cap and back, wings that are black grading into green and/or blue on the edges, and underparts that are gray. The bill is dark with a long, sharp point and the legs are orange. Female adults tend to be smaller, with duller and lighter plumage than that seen in males, particularly in the breeding season.
Coloration of immature herons is different. The neck and chest are striped with white and shades of brown. The back is also brown with white and beige spots. The coloration of immature and adult birds is quite cryptic in dense vegetation. (Hancock and Kushlan, 1984; Davis and Kushlan, 1994)
Range length: 41 to 46 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; male more colorful
Average mass: 175 g.
The oldest know wild green heron was a banded bird that was captured when it was almost 8 years old. There is very little information on lifespan in these birds.
Range lifespan
Status: wild: 11.6 (high) years.
Average lifespan
Status: wild: 95 months.
Green herons live along forested water margins. Their general distribution is limited by the availability of wetlands. They frequent both salt and fresh water, showing great flexibility in habitat choice. Favored habitats are mangrove-lined shores and estuaries, and dense, woody vegetation fringing ponds, rivers and lakes (Hancock and Kushlan, 1984).
Habitat Regions: temperate ; tropical ; terrestrial
Aquatic Biomes: lakes and ponds; rivers and streams; coastal
Wetlands: marsh
Other Habitat Features: riparian ; estuarine
Green herons have a wide range in North America, but are generally found near wetlands. They occur as far north as southern Canada and as far south as northern South America. They are found throughout the eastern United States as far west as North Dakota and the Great Plains states, although some sedentary populations occur on the west coast. During the breeding season they are found primarily in the eastern United States, with some populations in the Pacific Northwest as well. Non-breeding individuals are found in Mexico and Central America, Texas, southern New Mexico and Arizona, and the Caribbean islands. Small vagrant populations winter in Hawaii and the United Kingdom. Some populations migrate and others are sedentary populations. Sedentary populations occur along the east and west coasts of the United States and Central America. Most populations in North America, however, are migratory. After breeding they disperse southwards, in mid-September. Spring migration occurs from March to April, an earlier arrival than most other herons. (Davis and Kushlan, 1994; Hancock and Kushlan,1984)
Biogeographic Regions: nearctic (Native ); oceanic islands (Native )
Green herons are important predators of fish and invertebrates in the aquatic ecosystems where they live.
Green herons are enjoyed by birdwatchers.
Economic importance is minimal with negative effects on fishing (Davis and Kushlan, 1994).
Human activities have had their effect on the heron. Historically, green herons were sometimes hunted for food. Fish hatcheries kill green herons to regulate their populations and prevent them eating their young fish. Pesticides have been found to accumulate in heron tissues, but no evidence of general reproductive failure has been observed, despite some localized effects to herons in highly polluted areas. Eggshell thinning has been recorded in comparison with pre-1947 egg samples, but it is not considered lethal. Increased recreational and industrial use of river channels leads to decreased use by green herons. Yet this has not led to decreased use of backwater habitats, for example, ponds. The main concern for the heron has been conservation and management of wetlands as a whole, versus the drainage and development that depletes habitat in which they live. No populations are considered threatened or endangered (Davis and Kushlan, 1994).
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Green herons use their keen vision, hearing, and sense of touch to perceive their environment. They have especially acute vision that helps them to capture prey. Green herons have an elaborate set of calls and body postures that they use for communicating with other green herons. Examples are their elaborate courtship displays, warning calls when a predator is detected, and territorial displays.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Green herons are seasonally monogamous. Courtship displays are stereotyped. They begin with Flying Around displays resembling natural flight, but oriented to breeding sites with skow calls. From here, courtship becomes aggressive. Pursuit Flight, Circle Flight and Forward displays are used, where a rasping 'raah-raah' call exposes the red mouth-lining. Crooked-Neck Flight displays are more aggressive, where the neck is partially flexed, legs are dangled, and wingbeats are audible. Much like the Crooked-Neck Display, the Flap Flight Display shows the greatest intensity of flight displays. Here, the male lurches through the air with exaggerated flapping producing a whoom-whoom-whoom sound in a crooked-neck posture with crest, neck, and scapular feathers erect and often giving a roo-roo call before landing.
Nonaerial displays are interspersed with display flights. In the Snap Display, the male perches, then points body, head and neck down until bill tip is at or below the level of his feet and then snaps his mandibles together, producing a click while also erecting his feathers. The Stretch Display involves the male pointing his bill straight up, stretching his neck, and then bending it backwards until the head almost touches its back with interscapular plumes erect and fanned. In this posture, he sways his neck and head from side to side with crest, breast, and flank feathers sleeked back, eyes bulging, and iris possibly turning from yellow to deep orange while emitting an aaroo-aaroo sound.
Males perform this Stretch Display before a female is allowed to enter the eventual nest area. The female then performs a less intense Stretch silently after the male, which confirms the pair-bond. At this time, the male stops Flight and Snap displays. The pair then engages in mutual bill-snapping and feather nibbling, though those behaviors are reduced soon thereafter. Copulation occurs on the nest platform during the nest-building stage. It lasts about ten seconds with several hours between copulations. (Davis and Kushlan, 1994; Hancock and Kushlan, 1984)
Mating System: monogamous
After the last egg is laid, copulations cease and incubation persists for 19-21 days. A normal clutch is 2 to 4 eggs, laid in 2-day intervals. Fledging occurs when chicks are 16 to 17 days old, and independence is gained between 30 and 35 days.
Nesting takes place in forest and swamp patches, over water or in plants near water. Nesting pairs normally nest alone, but loose aggregations of mated pairs can form. Nest building is a cooperative effort, with the male participating more in protection versus actual construction. Nest placement can be from ground level to 20 meters, depending on plant height and thickness; branches in trees are favored. There is no attempt at nest sanitation, though chicks void over the edge of the nest once they're able to walk.
Breeding interval: Green herons breed once yearly.
Breeding season: The time of breeding varies considerably geographically, generally breeding begins anytime from March through July.
Average eggs per season: 2-4.
Range time to hatching: 19 to 21 days.
Range time to independence: 30 to 35 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Average eggs per season: 4.
Both adults feed and brood chicks, though at less frequent intervals as the chicks become more independent.
Parental Investment: altricial ; male parental care ; female parental care
Smaller and thinner than the American Bittern (Botaurus lentiginosus), the Green Heron (18 inches) is named for its back and wings, which are a dull greenish color in good light but may appear much darker when this heron is hidden well in vegetation. The Green Heron may also be identified by its dark brown neck, white throat, black bill, and black crest. Males and females are similar to one another in all seasons. The Green Heron is found widely across North and South America. In North America, this species breeds across the eastern United States and southern Canada, as well as on the Pacific coast of the U.S. In winter, Green Herons withdraw from the interior and from northern parts of their breeding range, and may be found along the coasts south from California and South Carolina as well as in Mexico and Central America. Coastal populations in the southern U.S. are non-migratory, as are most populations in the tropics. Green Herons breed in a variety of wetland habitats, both freshwater and saltwater, with tall vegetation for cover. In winter, Green Herons utilize similar types of habitats as in summer. Green Herons breeding or wintering in tropical environments also inhabit mangrove habitats. This species primarily eats small fish and amphibians. Due to the Green Heron’s small size and shy nature, individuals standing still in tall vegetation are often difficult to observe. Green Herons are easier to see while walking along the edge of the water, plunging their bills into the water to catch prey, or when flying away from the observer upon being spooked. This species is primarily active during the day, but may also hunt at night to avoid being spotted by its prey.
Smaller and thinner than the American Bittern (Botaurus lentiginosus), the Green Heron (18 inches) is named for its back and wings, which are a dull greenish color in good light but may appear much darker when this heron is hidden well in vegetation. The Green Heron may also be identified by its dark brown neck, white throat, black bill, and black crest. Males and females are similar to one another in all seasons. The Green Heron is found widely across North and South America. In North America, this species breeds across the eastern United States and southern Canada, as well as on the Pacific coast of the U.S. In winter, Green Herons withdraw from the interior and from northern parts of their breeding range, and may be found along the coasts south from California and South Carolina as well as in Mexico and Central America. Coastal populations in the southern U.S. are non-migratory, as are most populations in the tropics. Green Herons breed in a variety of wetland habitats, both freshwater and saltwater, with tall vegetation for cover. In winter, Green Herons utilize similar types of habitats as in summer. Green Herons breeding or wintering in tropical environments also inhabit mangrove habitats. This species primarily eats small fish and amphibians. Due to the Green Heron’s small size and shy nature, individuals standing still in tall vegetation are often difficult to observe. Green Herons are easier to see while walking along the edge of the water, plunging their bills into the water to catch prey, or when flying away from the observer upon being spooked. This species is primarily active during the day, but may also hunt at night to avoid being spotted by its prey.
The Green heron (Butorides virescens) is a small heron of North and Central America. Butorides is from Middle English butor "bittern" and Ancient Greek -oides, "resembling", and virescens is Latin for "greenish".[2]
It was long considered conspecific with its sister species the striated heron (Butorides striata), and together they were called "green-backed heron". Birds of the nominate subspecies (no matter which taxonomic arrangement is preferred) are extremely rare vagrants to western Europe—for example, a sighting in Pembrokeshire in 2018 was only the second recorded sighting in Wales;[3] individuals from the Pacific coast of North America may similarly stray as far as Hawaii.[4][5][6]
The green heron is relatively small; adult body length is about 44 cm (17 in). The neck is often pulled in tight against the body. Adults have a glossy, greenish-black cap, a greenish back and wings that are grey-black grading into green or blue, a chestnut neck with a white line down the front, grey underparts and short yellow legs. The bill is dark with a long, sharp point. Female adults tend to be smaller than males, and have duller and lighter plumage, particularly in the breeding season. Juveniles are duller, with the head sides, neck and underparts streaked brown and white, tan-splotched back and wing coverts, and greenish-yellow legs and bill. Hatchlings are covered in down feathers, light grey above, and white on the belly.[4][5][6]
The green heron's call is a loud and sudden kyow; it also makes a series of more subdued kuk calls. During courtship, the male gives a raah-rahh call with wide-open bill, makes noisy wingbeats and whoom-whoom-whoom calls in flight, and sometimes calls roo-roo to the female before landing again. While sitting, an aaroo-aaroo courtship call is also given.[5][6]
Measurements:[7]
As noted above, this species was formerly included in B. striata, which at that time was erroneously known as B. striatus. The Early Pleistocene B. validipes, whose fossil remains were discovered in Florida, might have been the ancestor of the green heron as the living species seems to replace the extinct relative in the fossil record.
Subspecies distinction is uncertain at best. The color variation between populations is less pronounced than between birds of the same population. Migratory populations are longer-winged than those resident year-round, but this cannot be used to delimit subspecies as it is quite obviously a consequence of differing habits and can be expected to undergo convergent evolution in unrelated populations of this species that just share the same habits. Thus, thorough molecular phylogenetic studies would be required to resolve the question of subspecies delimitation.
The following subspecies are commonly listed, though the validity of most of them is seriously disputed:[4]
Much of the dispute hinges upon the distinctness of the Caribbean and Central American populations, the second taxon in this species to be described. To describe the two most extreme views, some authors assemble the bulk of the mainland population in the nominate subspecies but treat the parapatric populations as distinct subspecies, while others place all resident populations in maculata and all migratory ones in virescens.
The habitat of the green heron is small wetlands in low-lying areas. The species is most conspicuous during dusk and dawn, and if anything these birds are nocturnal rather than diurnal, preferring to retreat to sheltered areas in daytime. They feed actively during the day, however, if hungry or provisioning young. Shore-living individuals adapt to the rhythm of the tides. They mainly eat small fish, frogs and aquatic arthropods, but may take any invertebrate or vertebrate prey they can catch, including such animals like leeches, earthworms, dragonflies, damselflies, waterbugs, grasshoppers, spiders,[9] crayfish,[10] prawns,[9] mice, other rodents, lizards, tadpoles and snakes.[10] Some of the many fish eaten are: minnows, sunfish, catfish, perch, eels and, in urban areas, goldfish.[10] Green herons are intolerant of other birds – including conspecifics – when feeding and are not seen to forage in groups. They typically stand still on shore or in shallow water or perch upon branches and await prey. Sometimes they drop food, insects, or other small objects on the water's surface to attract fish, making them one of the few known tool-using species. This feeding method has led some to title the green and closely related striated heron as among the world's most intelligent birds.[11] They are able to hover briefly to catch prey.[4][5][6]
The northern population moves to its breeding ranges during March and April; near the northernmost limit of the green heron's range, breeding is well underway by the end of May. The migration to the winter quarters starts in September; by late October, the birds are absent from regions where they do not stay all year. At least the northward migration does not seem to be affected by global warming; birds appear in their breeding ranges at the same time they did 100 years ago.[4][6][12][13]
Individuals of non-migratory populations abandon their territories after breeding season to roam about the region. They may or may not return to the previous year's breeding location, depending on whether they found better habitat during these wanderings. In these populations, the breeding season is determined by rainfall and consequent prey availability.[4][5][6]
Green herons are seasonally monogamous. The pairs form in the breeding range, after an intense courtship display by the males, who select the nesting sites and fly in front of the female noisily and with puffed-up head and neck plumage. They nest in forest and swamp patches, over water or in plants near water. Nests are a platform of sticks, often in shrubs or trees, sometimes on the ground. Locations in trees are preferred, with some nests built up to 20 m (66 ft) off the ground although heights of several meters are more common. Rarely, large numbers of these birds congregate in heronries for nesting.[4][5][6]
The clutch is usually 2–6 pale green eggs,[5] which are laid in 2-day intervals (though the second egg may be laid up to 6 days later than the first).[14] After the last egg has been laid, both parents incubate for about 19–21 days until hatching, and feed the young birds.[15] The frequency of feedings decreases as the offspring near fledging. The young sometimes start to leave the nest at 16 days of age, but are not fully fledged and able to fend for themselves until 30–35 days old. Sometimes – particularly in the tropical parts of its range – the green heron breeds twice a year.[4][5][6]
Green herons are one of the few species of bird known to use tools. In particular, they commonly use bread crusts, insects, or other items as bait. The bait is dropped onto the surface of a body of water to lure fish. When a fish takes the bait, the green heron then grabs and eats the fish.[16]
Nestlings
Subadult retaining some juvenile plumage
_young_adult.jpg)
Young adult B. v. virescens
Breeding plumage
Adult
Adult
.jpg)
Hunting in New York
_in_flight_Peten.jpg)
in Guatemala
Subspecies B. v. maculata with neck extended
The Green heron (Butorides virescens) is a small heron of North and Central America. Butorides is from Middle English butor "bittern" and Ancient Greek -oides, "resembling", and virescens is Latin for "greenish".
It was long considered conspecific with its sister species the striated heron (Butorides striata), and together they were called "green-backed heron". Birds of the nominate subspecies (no matter which taxonomic arrangement is preferred) are extremely rare vagrants to western Europe—for example, a sighting in Pembrokeshire in 2018 was only the second recorded sighting in Wales; individuals from the Pacific coast of North America may similarly stray as far as Hawaii.
