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Grey herons, like many other bird species, show aggression through use of their neck. When a threat or a nuisance draws near, grey herons perform a stabbing motion with their head and raise their crest. Even though grey herons have been spotted in interspecific groups, including gulls (Family Laridae), they generally maintain a safe distance from individuals of other species. Since they are not social birds, they have little need for other communication behaviors except during the breeding season. During the breeding season, grey herons use advertising calls to attract females. They produce a harsh cry similar to other herons. They follow this by stretching their wings and pointing their bill upwards to initiate preening. Like most birds, grey herons perceive their environments through auditory, visual, tactile, and chemical stimuli.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
The conservation status for grey herons is listed as least concern. Grey herons are widely distributed and relatively abundant, with an estimated world-wide population between 790,000 and 3,700,000 adults. Overall population size appears to be stable. The biggest threats to grey herons in the future are shooting and poisoning by fish farmers. Potential pollution impacts include calcium issues, thinning of eggshells, reproductive problems, and suppressed immune systems.
CITES: no special status
IUCN Red List of Threatened Species: least concern
Grey herons can have negative effects and potentially cause dramatic losses from fish farms, preying upon readily available fish and potentially spreading diseases through the farm. Grey herons can encourage the spread of common fish viruses and infectious diseases, such as pancreatic necrosis (IPN), viral haemorrhagic septicaemia (VHS), and spring viraemia of carp (SVC). Herons spread these diseases through regurgitated foods and excreted wastes.
Negative Impacts: crop pest; causes or carries domestic animal disease
Grey herons do not have any known economic benefits to humans.
Grey herons are important in limiting fish populations in estuaries, rivers, and other bodies of water. Their nests also provide shelter for rodents and insects.
Grey herons feed on a wide range of prey items but are primarily piscivores. In addition to fish (Class Actinopterygii), their diet consists of insects (Class Insecta), crustaceans (Subphylum Crustacea), frogs (Class Amphibia) and small mammals. They sometimes even ingest tiny birds. Recent studies have documented grey herons attempting to prey upon and consume white-throated rails (Dryomnas cuvieri aldabranus). This is the largest bird species upon which grey herons attempt to prey. While it is not clear how often grey herons succeed in feeding on rails, injuries have been noted after feeding attempts.
To locate food, grey herons wade through shallow water or move on land. They are thought to be most successful in capturing prey in the moonlight. Usually these herons stand still and wait for prey to approach in the water. They capture prey with their bills and generally swallow it whole, in one swift gulping action. Like other herons (Ardea species), grey herons in deeper water typically stand still on one foot and wait, sometimes for extended periods of time, for potential prey to swim near.
Animal Foods: birds; mammals; amphibians; reptiles; fish; insects
Primary Diet: carnivore (Piscivore )
Grey herons or common herons (Ardea cinerea) have an extensive geographic range. They are found throughout Eurasia and Africa. The northern-most extent of their range is restricted to regions that provide at least four months of warm weather. Grey herons also have been reported in areas of North America, Greenland, and Australia, areas typically considered outside of their natural range. This species is considered only partially migratory; thus, their range does not diminish significantly during winter or breeding seasons. A considerable number of individuals may migrate great distances to reach new breeding grounds, however. For example, European grey herons have been documented in portions of southern Europe.
Four subspecies of grey herons are recognized, each with relatively distinct geographic ranges: A. cinerea cinerea occurs in Europe, Africa, western Asia; A. cinerea firasa in Madagascar; A. cinerea jouyi in eastern Asia; and A. cinerea monicae on islands near Banc d'Arguin, Mauritania. Ardea cinerea monicae is considered by some to be a distinct species.
Biogeographic Regions: palearctic (Native ); oriental (Native ); ethiopian (Native )
Grey herons are very hardy and generally adapt well to new environments. However, for continuous habitation, grey heron populations require locations that experience at least four months of warm weather. These warmer periods are necessary for laying eggs and early development of chicks. Grey herons also require some type of shallow body of water, which they use as their primary forage sites. These bodies of water may include saltwater or brackish inlets and estuaries, freshwater rivers, streams, lakes, or marshes, and even aquacultures used in fish farming. Roosting requirements vary by geographic region; however, many individuals choose to roost in branches at or near the top of taller trees. If trees are unavailable, grey herons may roost in dense brush or undergrowth.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; chaparral ; forest
Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools; coastal ; brackish water
Wetlands: marsh ; swamp ; bog
Other Habitat Features: riparian ; estuarine
The average expected lifespan for grey herons is 5 years. Mortality is highest during the first year, at a rate of 67%. Mortality declines nearly 30% for the second year of life, and continues to fall as grey herons age. The oldest recorded age of a grey heron in the wild is 23 years, 9 months, and 2 days (more than four times their expected life span).
Range lifespan
Status: wild: 23 (high) years.
Average lifespan
Status: wild: 5 years.
Grey herons are comparable in size to great blue herons (Ardea herodias) of North America. Body length in grey herons typically ranges from 84 to 102 cm. Like all “great herons” (Ardea species), grey herons are fairly large birds. In contrast, other genera of herons (Family Ardeidae), such as pond herons (Ardeola species), rarely exceed average body lengths of 49 cm. Body weight of grey herons typically ranges from 0.226 to 1.36 kg. This species exhibits a distinct arched wing when flying, with a wingspan of 155 to 175 cm.
As their common name suggests, grey herons have predominantly grey plumage covering their wings, dorsum, and most of the neck. Subspecies Ardea cinerea monicae is distinguished by its lighter plumage and shorter crest. In all grey heron adults, the head is white with long black feathers that extend from the eyes to the beginning of the neck, forming a large, impressive crest. Juveniles retain a dark crown of grey feathers into their first winter, after which they begin to develop the white forehead and distinctive black crest typical of adults. Grey herons have yellow bills through most of the year, but these acquire an orange tint during the breeding season. As with other herons (Family Ardeidae), grey herons fly with their head pulled back toward the body while keeping their legs extended behind them. This body positioning during flight distinguishes herons from cranes (Family Gruidae), which fly with their neck extended.
Range mass: 0.226 to 1.36 kg.
Range length: 84 to 102 cm.
Range wingspan: 155 to 175 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; male larger
Foxes (Canidae, usually Vulpes species) are the primary predators of grey herons. Crows (Corvus species) may feed upon grey heron eggs, but typically only eggs that have already been abandoned. Human activities, particularly hunting, capturing, and polluting, often are responsible for grey heron mortality.
Known Predators:
At the beginning of the breeding season, grey heron males select nesting sites. After choosing a suitable site, they make low grating calls to attract potential mates. Provided there are not multiple females approaching a single male, females choose a mate by approaching the males nesting site. Like great blue herons, both sexes must consent before pairing and mating occurs. Disinterested males often chase females from their nesting site to demonstrate their lack of interest. Once a male attracts a female to its nesting site, it begins a series courtship behaviors that include neck stretching, thrusting, and bowing. These lunging and bitterning displays, along with bill clapping, comprise most of the courtship dance performed by males to impress females. If the female remains at the site, the pair engages in mutual grooming behaviors called allopreening. At this point, the male and female have formed a monogamist pair that will remain together throughout the breeding season.
Mating System: monogamous
The breeding season for grey herons begins as early as February and continues through May or early June. At the beginning of the breeding season, each male selects a nest site, most often situated in the branches of tall trees. Nests also have been reported in dense undergrowth and occasionally on bare ground. Grey heron nests are constructed from nearly any materials the male can gather; most often these materials include sticks and grasses. Once made, a nest will be used repeatedly from season to season, with subsequent nests built upon those of previous years. Larger, more developed nests are desirable and quickly taken, usually by older males. These are guarded fiercely until paring and copulation have occurred.
Grey herons generally lay and raise one brood during the breeding season. However, if a brood is lost, it is not uncommon for herons to produce a replacement brood. Two broods from the same pair are considered a very rare occurrence, but have been recorded. Typically, females lay two to five eggs over a period of two or more days. Eggs are light blue-green in color. The number of eggs laid depends on the area in which the heron lives and the favorability of environmental factors; clutches as small as a single egg or as high as 10 eggs have been observed. Eggs typically take 25 to 26 days to incubate and hatch. Hatchlings compete with one another for food and parental care during early development, and commonly push one another from the nest. Hatchlings also have been reported to cannibalize deceased nest mates. Hatchlings fledge after approximately 50 days. However, despite leaving the nest, fledglings are not completely independent until 9 to 10 weeks. These offspring will be sexually mature by the following breeding season.
Breeding interval: Grey herons breed once a year.
Breeding season: Grey herons breed from late Feburary to early June.
Range eggs per season: 3 to 5.
Range time to hatching: 25 to 26 days.
Average fledging age: 50 days.
Range time to independence: 9 to 10 weeks.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Both male and female grey herons contribute to providing for and protecting their young. During nest building, most supplies are gathered by males. Construction of the nest is coordinated by females. Males aggressively defend females and unhatched eggs. Once hatched, both parents provide food to their offspring. Initially, young are fed directly. Later, parents regurgitate food onto the nest, where hatchlings must compete for food resources. Young remain with their parents for an extended period of time after they have fledged and are capable of leaving the nest.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Protecting: Male); pre-hatching/birth (Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
