About Egretta gularis (Bosc, 1792)
Common Name and Plumage Morphs
Egretta gularis (Bosc, 1792), commonly called the western reef heron, has two primary plumage color forms: an all-white morph and a dark grey morph. Intermediate grey shades, which may be linked to age, and grey-and-white particolored plumage can also occur.
White Morph Identification
The white morph resembles the little egret in general appearance, but differs in having a larger, yellower bill, more extensive yellow coloration on thicker legs, and very active foraging behavior that sometimes includes moving or shading the water surface with a wing.
Grey Morph Identification
The grey morph has a whitish throat, with a bill and legs similar to the white morph, and is unlikely to be confused with any other species within this egret's range.
Breeding Season Physical Traits
During the breeding season, the legs and facial skin turn reddish, and breeding individuals grow two long feathers on the sides of the nape.
Subspecies Count
There are two widely recognized subspecies.
Nominate Subspecies Range and Bill Trait
The nominate subspecies E. g. gularis ranges from West Africa to Gabon, with a small number of birds breeding in southern Europe. It has a more pointed bill than the other subspecies.
E. g. schistacea Range and Bill Trait
Subspecies E. g. schistacea (Hemprich & Ehrenberg, 1828) breeds from the Persian Gulf along India's coast to the eastern end of the Indian Peninsula, and has a larger bill that is particularly wide toward the base.
Related Distinct Species
The population on the eastern coast of South Africa is usually separated as the distinct species dimorphic egret, Egretta dimorpha.
Plumage Morph Genetic Basis
The dark and white morphs of Egretta gularis are thought to be controlled by a single allele, with the dark character incompletely dominant over the allele for white plumage.
Overall Species Range
This species occurs mainly on tropical coasts, ranging from West Africa through the Red Sea and Persian Gulf (Iran) east to India. It is also found in the Lakshadweep Islands and Sri Lanka, where breeding was once recorded at Chilaw.
Nominate Subspecies Breeding and Occurrence Range
The nominate subspecies breeds in West Africa from Mauritania to Gabon, and can sometimes be found outside the mainland, for example in the Canary Islands; small numbers breed in Spain.
E. g. schistacea Occurrence and Breeding Range
Subspecies schistacea occurs from the Red Sea coast eastward around the Indian coast, and breeding colonies are known from India's east coast near Pulicat Lake.
Inland Range Occurrence
Individuals occasionally range further inland.
Nominate Subspecies Vagrant Range
The nominate subspecies occurs as a vagrant in North America, South America, and the Caribbean islands. A growing number of records leads to suspicion that this subspecies may establish breeding colonies in Brazil.
European Escapee Records
Several records from Germany, Austria, and France between 1980 and 1990 have been linked to birds that escaped from an animal dealer in Mittelfranken.
Foraging Behavior
Western reef herons stalk their prey in shallow water. They often run or stir the water with their feet, or flick their wings to disturb prey, but may also stand still to ambush prey.
Diet
Their diet includes fish, crustaceans, and molluscs, and they regularly feed on mudskippers in coastal areas.
Prey Strike Adaptation
Laboratory studies show the species is capable of correcting strikes for light refraction at the water surface, but the probability of missing a target increases when striking at prey at very acute angles to the surface.
Vocalizations
Like other herons and egrets, they have few vocalizations, producing only a low kwok or grating sounds when disturbed or near the nest.
Breeding Habitat
The western reef heron's breeding habitat is coastal wetlands.
Red Sea Breeding Season
In the Red Sea region, the breeding season runs from June to August.
West Africa Breeding Season
The nominate subspecies breeds in West Africa from late April to September.
India Breeding Season
In India, breeding occurs during the monsoon rains from April to August.
Sri Lanka Breeding Season
At the former Chilaw breeding colony in Sri Lanka, breeding runs to the end of May.
Gujarat Breeding Colony Location
Most breeding colonies in Gujarat, western India, are located in mangroves.
Colony Composition
They nest in colonies that are usually made up of only their own species, but sometimes include other egrets and smaller herons.
Nest Structure
Nests are stick platforms built in trees or shrubs.
Nest Construction Roles
Males collect the nest sticks, while females arrange them to form the platform.
Nest Height Range
Nest heights generally range from about 5 to 15 meters, but nesting as low as 0.6 meters has been observed in mangrove trees growing in salt pans.
Clutch Traits
The usual clutch is three to four light blue eggs, matching the egg color of the little egret.
Incubation Start Effect
Incubation begins after the first egg is laid, which results in size disparities among hatched chicks.
Incubation Period and Roles
Both parents take turns incubating, and eggs hatch after about 23 to 24 days.
Hatchling Appearance
Hatchlings are white with grey dappling.
Chick Mortality Cause
Young birds sometimes die after falling from the nest platform.
Chick Care Behavior
Adults shade chicks during the hottest parts of the day.
Nest Predators
Rats prey on eggs, while cats and crows may take young chicks.
Nest Guarding Behavior
Adults typically guard the nest when eggs or young chicks are present.
Chick Feeding Behavior and Diet
Adults feed young by regurgitating semi-digested food at the nest, and this diet consists mainly of small fish from the families Clupeidae, Gobiidae, and Engraulidae.
Fledging Period
Young birds leave the nest approximately one month after hatching.
