Ardea herodias

At over a metre and half in height, the great blue heron is the largest heron in North America and one of the continent's most recognisable wading birds (2) (3). There are two main colour morphs of this statuesque species: a dark form that is mostly blue-grey, with chestnut thighs, and a white cap over a black eye stripe that merges into long, black plumes; and a light form which is all white. The neck, legs and wings are characteristically long, the tail is short, and the yellowish bill is thick, elongate and tapered. In flight, it coils its neck back into a distinctive s-shape, extends its legs back along its body axis, and beats its wings with steady, powerful strokes (2) (3) (4). Although the sexes are similar in appearance, the female is normally around ten percent smaller than the male, while juveniles are duller and lack the long plumes of the adults (4) (5). Considerable uncertainty surrounds the separation of subspecies of the great blue heron, with between two and seven recognised for North America alone (4). However, five main subspecies, that differ in size and plumage and occupy different parts of the species overall range, are commonly referred to: Ardea herodias herodias, A. h. fannini, A. h. wardii, A. h. occidentalis (the white form), and A. h. cognata (2) (4).

The largest heron in North America north of Mexico, the Great Blue Heron is, for the most part, an easy bird to identify. At 42-52 inches, its gray-blue back, buff neck, yellow bill, white face, and long, black facial plumes help to distinguish it from most other waders in its range. The all-white Caribbean subspecies, which enters our area in south Florida, may be distinguished from the similarly-colored Great Egret by its yellow legs and feet. Male and female Great Blue Herons are similar at all times of the year. The Great Blue Heron breeds across the majority of the United States and southern Canada. Great Blue Herons that breed in southern Canada and the northern Great Plains migrate south for the winter, when they may be found in Central America and the Caribbean. Populations living in most of the U.S.are non-migratory. This species is absent from the desert southwest and from high elevations of the Rocky Mountains. Great Blue Herons live in and around small bodies of water. In summer, Great Blue Herons nest in colonies, called ‘rookeries,’ surrounding lakes and ponds. They may nest either in trees, in bushes, or on the ground. This species utilizes similar habitats during the winter. Great Blue Herons mainly eat fish, but may also take crustaceans and small vertebrates (such as frogs, lizards, and mice) when the opportunity arises. Great Blue Herons may be best observed wading in shallow water, where they may be seen plunging their bills into the water to catch fish. It is also possible to see Great Blue Herons at their rookeries, especially when they return to roost at sunset, or while flying with their feet extended and their necks pulled in. Great Blue Herons are primarily active during the day.

Threat Status: Least concern

Foraging alone or in flocks, the great blue heron usually hunts by slowly wading or standing motionless in shallow water (2) (4). Although fish form the bulk of its diet, it will also take amphibians, invertebrates, reptiles, mammals and birds. When prey is sighted, it rapidly thrusts its neck forward to snatch the hapless quarry within its bill, and then typically swallows it whole (2) (3). As an alternative to walking or standing, it also occasionally exhibits a range of other foraging techniques that enable it to access deeper water where it is unable to wade. This includes hovering above the water, plunging beneath it, and simply swimming on the surface (4). Generally, the great blue heron nests in tall trees that are near to aquatic feeding areas, and are to some extent isolated from human disturbance (4). However, when trees are not available, it will also nest on the ground in areas free from predators, and in reeds, shrubs and mangroves (2). Although some nest singly, many breed in colonies, which vary in size depending on the amount of nearby foraging habitat (2) (4). Mates and nest sites change from year to year, with the consequence that mate selection is a critical part of the yearly cycle (4). Usually the male secures a display site first, such as an old nest, before engaging in an elaborate courtship display that includes an impressive repertoire of stretching, snapping, twig shaking, crest raising, and circling flight. After forming a pair and mating, the female lays between two to seven pale blue eggs, which are then incubated by both parent birds for around 28 days. The young are fed regurgitated food and fledge the nest after around 60 days (2) (4). The seasonal movements of the great blue heron is very much dependant on its location (3) (4). Herons from north-central North America migrate south over winter, whilst those closer to the either coast are more variable in their movements, with some remaining year round in the same location (2) (4).

Ardea herodias is a tall, long-necked wading bird of the Order Ciconiiformes (herons and storks), and is the largest of the North American herons. The sexes are similar in this species, with overall body color a dull blue-gray. It has a thick yellow bill, black shoulders, and legs that generally match the body color. A major identifying trait is the white face that has a black streak extending from behind the eye to the back of the head.

Great blue herons can be found in Canada, the United States, Central and South America. These birds migrate and may spend different seasons in different regions. During the spring and summer, they breed throughout North and Central America, the Caribbean, southern Canada and the Galapagos Islands. Some populations migrate to Central and South America during the winter months, but do not breed there.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

Gulf of Maine, Gulf of Mexico, North West Atlantic, Portuguese Exclusive Economic Zone, Spanish Exclusive Economic Zone

North America

Great blue herons can be found in the Nearctic and Neotropical regions. During the spring and summer, they breed throughout North and Central America, the Caribbean, much of Canada and the Galapogos. Some populations migrate to Central and South America during the winter months, but do not breed there.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: southeastern Alaska and southern Canada to southern Mexico, Greater Antilles, Virgin Islands (St. Thomas and Anegada), islands off coastal Venezuela, and on Galapagos. NON-BREEDING: southeastern Alaska, central U.S., and southern New England south to northern South America (mainly to northern Colombia, northern Venezuela). In the U.S. in winter, the highest densities occur along the lower Colorado River, around the Great Salt Lake, and near Aransas National Wildlife Refuge on the Texas coast (Root 1988). Wanders widely outside usual range, a few times to Hawaii. Some subadults may spend summer in nonbreeding range.

A. herodias occurs throughout most of North America, including Alaska, Quebec and Nova Scotia. The range extends south through Florida, Mexico and the Caribbean to South America, including the Galapagos Islands. A. herodias is distributed throughout the Indian River Lagoon.

The great blue heron breeds throughout much of North America, Central America, and on numerous Caribbean Islands, and the Galapagos (4). The subspecies Ardea herodias herodias occurs over most of North America; A. h. fannini occupies the northwest of North America; A. h. wardii is found in the eastern USA, from Kansas to Florida; A. h. occidentalis inhabits extreme southern Florida, the Caribbean and Mexico; and A. h. cognata is restricted to the Galapagos (2) (4).

Great blue herons are the largest herons in North America. They stand approximately 60 cm tall and are 97 to 137 cm long. They weigh 2.1 to 2.5 kg. They are tall waterbirds with long, S-shaped necks that have shaggy feathers. They have long, rounded wings, long pointed bills, and short tails. The bills are a yellowish color and the legs are yellowish-green to gray. Great blue herons have gray upper bodies, and their necks are streaked with white, black and rust-brown. They have gray feathers on the back of their necks with chestnut colored feathers on their thighs. They feature a plume of black feathers that starts behind their eyes and extends out behind their heads. Males tend to be slightly larger than females.

Young great blue herons are overall darker in color. They have dark gray crowns and many dark gray streaks on their necks. Young great blue herons do not have plumes on their heads or shaggy neck feathers like adults have.

Range mass: 2.1 to 2.5 kg.

Range length: 97 to 137 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike; male larger

Great blue herons are the largest herons in North America. They stand approximately 60 cm tall and are 97 to 137 cm long. They weigh 2.1 to 2.5 kg. They have long, rounded wings, long bills that taper to a point at the end, and short tails. They also have very long necks and legs. The bills are a yellowish color and the legs are green. Great blue herons have gray upper bodies, and their necks are streaked with white, black and rust-brown. They have grey feathers on the back of their necks with chestnut colored feathers on their thighs. The males have a puffy plume of feathers behind their heads and also tend to be slightly larger than females.

Range mass: 2100 to 2500 g.

Range length: 97 to 137 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

Length: 117 cm

Weight: 2576 grams

The largest heron in North America, great blue herons attain a height of 38 inches, with a wingspan of 70 inches.

Great blue herons always live near sources of water, including rivers, lake edges, marshes, saltwater seacoasts, and swamps. They require tall trees near water to nest in, and often nest in groups or "rookeries" which require a stand of suitable trees. They have been found breeding at elevations of up to 1,500 m. Most tend to avoid marine habitats along the east coast and instead live inland.

Range elevation: 1500 (high) m.

Habitat Regions: temperate ; tropical ; freshwater

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Wetlands: marsh ; swamp

Other Habitat Features: riparian

rivers, lake edges, marshes, saltwater shores, and swamps

Systems

• Terrestrial
• Freshwater
• Marine

Great blue herons always live near sources of water, including rivers, lake edges, marshes, saltwater seacoasts, and swamps. They usually nest in trees or bushes that stand near water, breeding at elevations of up to 1,500 m. They tend to avoid marine habitats along the east coast and instead live inland.

Range elevation: 1500 (high) m.

Habitat Regions: temperate ; tropical ; freshwater

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Wetlands: marsh ; swamp

Other Habitat Features: riparian

Depth range based on 8543 specimens in 1 taxon.
Water temperature and chemistry ranges based on 1 sample.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 15.833 - 15.833
  Nitrate (umol/L): 0.361 - 0.361
  Salinity (PPS): 33.335 - 33.335
  Oxygen (ml/l): 5.746 - 5.746
  Phosphate (umol/l): 0.382 - 0.382
  Silicate (umol/l): 2.546 - 2.546
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Comments: Freshwater and brackish marshes, along lakes, rivers, bays, lagoons, ocean beaches, mangroves, fields, and meadows. Nests commonly high in trees in swamps and forested areas, less commonly in bushes, or on ground, rock ledges, and coastal cliffs. Often nests with other herons. See Spendelow and Patton (1988) for further details and discussion of geographic variation in nesting sites. Generally nests close to foraging habitat.

Found in a diverse range of habitats including salt marsh and mangrove swamps, freshwater marshes and swamps, estuaries, coastal lagoons, flooded fields, ditches, riverbanks, and lake edges (4).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Migrates to northern breeding range February-early May; departs northerly localities September-October. Disperses in all compass directions after breeding, before southward migration. Southern populations may be quite sedentary. Present in small numbers in Colombia mainly October to mid-April, in Panama mainly September-April (Ridgely and Gwynne 1989, Hilty and Brown 1986).

Great blue herons fish primarily during the day or occasionally at night, but most of their activity occurs around dawn and dusk. Herons use their long legs to wade in shallow water and their sharp spear-like bills to catch their food. Great blue herons' diet consists of mainly fish, but also includes frogs, salamanders, lizards, snakes, young birds, small mammals, shrimp, crabs, crayfish, dragonflies, grasshoppers and many aquatic invertebrates. Herons locate their food by sight and usually swallow it whole. Herons have been known to choke on prey that is too large. Great blue herons obtain water by scooping up water with their bills and tipping their heads back to drink. Great blue herons live in aquatic habitats and are surrounded by water for nearly their entire lives.

Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; aquatic crustaceans

Great blue herons fish in both the night and the day, with most of their activity occurring around dawn and dusk. Herons use their long legs to wade in shallow water and their sharp "spearlike" bills to catch their food. Great blue herons' diet consists of mainly fish, but also includes frogs, salamanders, lizards, snakes, birds, small mammals, shrimps, crabs, crayfish , dragonflies, grasshoppers, and many other aquatic insects. Herons locate their food by sight and usually swallow it whole. Herons have been known to choke on prey that is too large.

Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

Comments: Eats fishes, insects, crustaceans, amphibians and reptiles, mice and shrews, and other animals. Forages mostly while standing in water but also in fields; sometimes drops from air or perch into water (Palmer 1962, Terres 1980).

As large wading birds, great blue herons are able to feed in deeper waters, and thus are able to exploit a niche not open to most other heron species. Primary feeding behaviors in this species include standing crouched, standing upright, and wading slowly. Great blue herons have high striking efficiency (the percentage of strikes that result in the capture and ingestion of prey) when standing crouched on banks. However, this behavior is used less often than either standing upright or wading slowly. This suggests that the goal for great blue herons may not be achieving maximum feeding efficiency; but rather, maximizing food intake through the infrequent capture of high quality prey (Willard 1977). Data seem to reinforce this point, as it has been shown that great blue herons that utilize the rather inefficient slow wade as a feeding strategy tend to feed upon more large fish such as eel and perch (Willard 1977).In a Canadian study of great blue herons, Butler (1993) found that A. herodias fed primarily upon sticklebacks, shiners, sea perch, pipefish, sculpins, etc., and that they require approximately 30% more energy above basal metabolic costs to fuel their activities.Activity Time: Butler (1993) stated that the nocturnal feeding behavior observed in great blue herons was important to resource partitioning and reduced competition among wading birds. In a Cedar Key, Florida study, Black and Collopy (1982) found great blue herons to be equally active in either daylight or evening hours, though most evening feeding occurs during early evening low tides than later in the evening.

Great blue herons control fish and insect populations in many different habitats. They are also an important source of food for the animals that prey on them.

Corvus caurinus and Corvus corax have been reported eating heron eggs. Eagles, Procyon lotor, bears, Cathartes aurata, and Buteo jamaicensis prey on the young birds and sometimes even the adults. Birds often abandon a rookery where they have been living after a predator has killed an adult or chick in the area.

Nesting in rookeries is a way for great blue herons to avoid predation. If a heron nests within a large group, there are many more eyes and ears to keep watch for predators. Also, the chances that one particular nest will be predated decreases significantly when there is a high density of nests.

Known Predators:

• Northwest crows (Corvus_caurinus)
• Common raven (Corvus_corax)
• Eagles
• Raccoons (Procyon_lotor)
• Bears
• Turkey vultures (Cathartes_aura)
• Red-tailed hawks (Buteo_jamaicensis)

Great blue herons control fish and insect populations in many different habitats. They are also an important source of food for the animals that prey on them.

Northwest crows and common ravens have been reported eating heron eggs. Eagles, racoons, bears, turkey vultures, and red-tailed hawks prey on the young birds and sometimes even the adults. Birds will abandon a colony where they have been living after a predator has killed an adult or chick in the area.

Known Predators:

• crows and ravens
• common raven
• eagles
• raccoons
• bears
• turkey vulture
• red-tailed hawks

A. herodias is generally considered a solitary feeder, though it has been observed to associate with other wading birds of various sizes while feeding. While breeding, A. herodias avoids mixed flocks in favor of nesting in monospecific colonies.

Ardea herodias preys on:
Paralichthyes albigutta
Strongylura marina
Leiostomus xanthurus
Cyprinus carpio
Carassius auratus
Pimephales notatus
Lepomis macrochirus
Pseudacris triseriata
Chelydra serpentina

Based on studies in:
USA: Florida (Estuarine)

This list may not be complete but is based on published studies.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

The great blue heron is generally the most well known and widespread heron species in North America. It is common throughout the Indian River Lagoon.

Nonbreeding: usually solitary. May establish feeding territories in winter (Stiles and Skutch 1989).

Great blue herons are relatively quiet compared to other related species. Their main call is a soft "kraak" when they are disturbed in flight. Other heron calls include a "fraunk" when they are disturbed near their nests which usually lasts about 20 seconds, and an "ar" when they are greeting other members of their species. These herons are known to have up to 7 different calls. They also snap their bills together, raise their feathers, and shake twigs in courtship displays.

Communication Channels: visual ; acoustic

Great blue herons are relatively quiet compared to other related species. They release a soft "kraak" when they are disturbed in flight. Other heron calls include a "fraunk" when they are disturbed near their nests which usually lasts about 20 seconds, and an "ar" when they are greeting other members of their species. These herons are known to have up to 7 different calls. They also snap their bills together and use complicated body movements in courtship displays.

Communication Channels: visual ; acoustic

Comments: Generally tends to be mainly crepuscular but also is active in daytime and at night. In coastal region, activity often is related to the tidal cycle, independent of day-night cycle in some areas (Powell 1987). Nocturnal foraging activity occurs in nontidal situations as well as in tidal environments (McNeil et al. 1993).

The oldest wild great blue heron was said to be 23 years old, but most do not live so long. The average lifespan for a great blue heron is around 15 years. As with most animals, they are most vulnerable when they are young. More than half of the great blue herons born in one year will die before they are a year old.

Range lifespan
Status: wild: 24.5 (high) years.

Average lifespan
Status: wild: 15 years.

Average lifespan
Status: wild: 294 months.

The oldest wild great blue heron was said to be 23 years old, but most do not live so long. The average lifespan for a great blue heron is around 15 years. As with most animals, they are most vulnerable when they are young. More than half (69%) of the great blue herons born in one year will die before they are a year old.

Range lifespan
Status: wild: 24.5 (high) years.

Average lifespan
Status: wild: 15 years.

Average lifespan
Status: wild: 294 months.

Maximum longevity: 24.5 years (wild)

Great blue herons generally have one mate per breeding season. Males will perform courtship displays to attract a female. A male will perch at his nest, stretch his neck and fluff his plume of neck feathers. He may also fly in a circle around his nest or shake twigs to impress a female. Once he gets the attention of a potential mate, she perches next to the male and they will both raise their crest feathers and clatter their beaks together. Pairs may repeat these behaviors throughout the breeding season.

Mating System: monogamous

Great blue herons use large nests mainly of bare sticks and branches. These herons prefer to nest in tall trees and most nests are built 9 to 21 m off the ground. Great blue herons often nest in large groups, or rookeries, with other herons.

Great blue herons typically breed from March to May in the northern part of their range and November through April in the southern hemisphere. Females lay between 2 and 7 pale-blue eggs. Both parents take turns incubating the eggs, which hatch after 26 to 30 days. After living in the nest for about 2 months, the chicks are ready to fledge, which means they are old enough to leave the nest and survive on their own. Herons are usually old enough to reproduce when they are about 22 months old.

Breeding interval: Great blue herons breed once yearly.

Breeding season: Breeding occurs from March to May in northern parts of their range and November to April in southern parts of their range.

Range eggs per season: 2 to 7.

Average eggs per season: 3 to 5.

Range time to hatching: 26 to 30 days.

Range fledging age: 56 to 60 days.

Average age at sexual or reproductive maturity (female): 22 months.

Average age at sexual or reproductive maturity (male): 22 months.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average eggs per season: 4.

Both great blue heron parents care for the young. Males and females build a stick nest, high in a tree. Parents take turns incubating the eggs, and after the eggs have hatched they will take turns caring for the chicks. The young herons are born helpless and rely on their parents for warmth, protection, and food. Chicks are fed mostly fish.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

Great blue herons generally have one mate per breeding season.

Mating System: monogamous

Great blue herons typically breed from March to May in the northern part of their range and November through April in the southern hemisphere. Females lay between 2 and 7 pale blue eggs. Birds living further north tend to have more eggs. Both parents incubate the eggs, which means that the parents take turns sitting on the nest to keep the eggs warm until they hatch. The eggs hatch after 26 to 30 days of incubation. After living in the nest for about 2 months, the babies (called chicks) are ready to fledge, which means they are old enough to leave the nest and survive on their own. Herons become sexually mature when they are about 22 months of age.

Breeding interval: Great blue herons breed once yearly.

Breeding season: Breeding occurs from March to May in northern parts of their range and November to April in southern parts of their range.

Range eggs per season: 2 to 7.

Range time to hatching: 30 (high) days.

Average time to hatching: 27 days.

Range fledging age: 60 to 81 days.

Average age at sexual or reproductive maturity (female): 22 months.

Average age at sexual or reproductive maturity (male): 22 months.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average eggs per season: 4.

Both parents care for and feed the chicks until they are ready to leave the nest. The largest chicks receive the most food.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

Clutch size is 3-7, averages larger in north than in south. Incubation, by both sexes, lasts 25-29 days. Both parents tend young, which leave nest in 60-90 days. May breed at 2 years. Nests usually in colonies, a few pairs to 100s; sometimes solitary. Fledging success depends importantly on success of parents in providing sufficient food when nestlings are 2-6 weeks old (Bennett et al. 1995, Auk 112:201-209).

Though sympatric with other species of wading birds, the great blue heron forms monospecific breeding colonies. This behavior differs from species such as the snowy egret and white ibis that nest in large mixed flocks. Colony size in great blue herons can be large, ranging between 5 - 500 nests per colony, with an average of approximately 160 nests per colony.Nesting in the Florida Everglades and Lake Okeechobee begins between late November through mid-March and April, with nests sometimes located as high as 20 m above the ground (Butler 1993; Smith 1997). Clutch size ranges from 3 - 6 eggs, with 1 brood being raised each year. Should eggs be abandoned or destroyed, a replacement clutch can be laid (Ehrlich et al. 1988).Reproductive success in great blue herons is limited by the ability of parent birds to gather food. Energy availability (as measured in food resources) appears, in part, to determine when eggs will be laid. Butler (1993) observed that egg laying in great blue herons occurs after a threshold level for successful egg laying is surpassed for several consecutive days. Chicks are generally present after parental food availability peaks. This leads to a potential problem in nourishing nestlings. Parental birds have been shown to consume up to 4 times as much food when they are feeding young chicks than when egg laying or incubating eggs (Butler 1993); however, chicks do not reach their metabolic peak until approximately 26 - 41 days after birth. Thus, if food availability has already peaked before chicks appear, it is then potentially more difficult for parents to nourish nestlings. There is some data to support this view. Collazo (1981) found that starvation was not only the primary cause of nestling mortality, but that it most often coincided with the peak energy demands of 3 - 6 week old chicks.A. herodias is negatively affected by human disturbance, particularly during the early stages of the breeding cycle. Repeated human intrusion into nesting areas often results in nest failure, with abandonment of eggs or chicks (Carlson and McLean 1996). Great blue herons thus tend to choose nest sites in undisturbed wetland areas around lakes or rivers, well removed from roads (Gibbs and Kinkel 1997) and other signs of human activity. In one Ohio study, foot traffic was observed to be the most detrimental disruption to breeding great blue herons, sometimes leading to nest abandonment. Nesting birds were shown to tolerate routine mechanical disturbance, even if loud, as long as no humans were nearby (Carlson and McLean 1996). Nest success increased when nest sites were chosen near barriers such as fencing, ditches or moats that excluded human intrusion. Nests located in areas with this type of buffer zone, even if small in overall area, had higher nest success and fledging rates than those located near disturbed areas.

Eggs are incubated for approximately 28 days and hatch asynchronously over a period of several days (Custer and Peterson 1991). The first chick to hatch becomes more experienced in food handling and aggressive interactions with siblings, and so often grows at a faster rate than its nestmates. Male and female chicks show little difference in hatching weight, but males tend to grow somewhat faster than females. By the time fledging occurs, males often weigh up to 13% more than females. Young fledge after 56 - 60 days (Ehrlich et al. 1988).

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 4 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 4
Specimens with Barcodes: 9
Species With Barcodes: 1

This is the most well-known and most widespread heron in North America. Human interference with the heron primarily involves destruction of habitat. Many herons are also killed each year due to collisions with utility wires. As a migratory species, great blue herons are protected by the United States Migratory Bird Treaty Act. Great blue herons have no special protection in the state of Michigan since their populations are large and healthy.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

This is the most well-known and most widespread heron in North America. Human interference with the heron primarily involves destruction of habitat. Many herons are also killed each year due to collisions with utility wires. Great blue herons are protected by the United States Migratory Bird Treaty Act.

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

Canada

Rounded National Status Rank: N5B - Secure

United States

Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding

Rounded Global Status Rank: G5 - Secure

Classified as Least Concern (LC) on the IUCN Red List (1).

Global Short Term Trend: Relatively stable (=10% change)

Comments: Populations generally are stable or increasing in most areas. See Spendelow and Patton (1988) for status of coastal U.S. breeding populations. Populations in the south-central U.S. may be benefiting from crayfish aquaculture; bird population increases may be related to favorable foraging opportunities afforded by expanding crayfish aquaculture (herons may prey on small fishes often abundant in ponds) (Fleury and Sherry 1995).

Comments: In Illinois, a public viewing area used once a week by humans 229 m from a rookery did not cause any overt responses from nesting birds (DeMauro 1993). See Vos (1984) for information on response to human disturbance in Colorado.

Great blue herons are among the most well known and most common of the wading bird species. It is not federally listed as either threatened or endangered, nor is it listed in Florida as a Species of Special Concern (SSC).Benefit in IRL: The environmental sensitivity of wading birds, coupled with the relative ease of assessing their numbers, makes them attractive as biological indicators of ecosystem health and habitat quality (Custer and Osborn 1977; Powell and Powell 1986; Powell et al. 1989).

The great blue heron has a remarkable ability to exploit a wide range of habitats and food types. Consequently it is widespread and abundant, and is not subject to any major threats at the species level (4) (6). Nonetheless, some populations, particularly those occupying small areas on the coast, are vulnerable to localised impacts (4). This broadly includes habitat destruction, human disturbance and persecution, and contamination by pollutants (2) (4).

Critical to the conservation of threatened populations of the great blue heron is the protection of nesting sites and feeding habitats, and the conservation of food supplies (2) (4). This is already being achieved by initiatives such as the Heron Working Group, the primary goal of which is to ensure a viable and self-sustaining population of the Pacific great blue heron (A. h. fannini) (7).

People who create and stock fish ponds may find that their expensive fish are being eaten by great blue herons. This can be prevented by installing bird netting or using decoy herons to scare the birds away.

Great blue herons are a delight to watch and are important members of healthy, freshwater ecosystems.

People who create and stock fish ponds may find that their expensive fish are being eaten by great blue herons. This can be prevented by installing bird netting or using decoy herons to scare the birds away.

Great blue herons are a delight to watch and are important members of healthy, freshwater ecosystems.

Positive Impacts: ecotourism