The Slaty Egrets or Herons (Egretta vinaceigula) – also known as Brown-throated or Red-throated Egrets – are small, dark egrets that occur naturally in South Central Africa.
Until 1971, there were considered a color phase of the more widespread Black Heron (Egretta ardesiaca); however, they have been separated based on consistent physical characteristics, such as yellow legs and the vinous brown throats, as well as some behavioral differences.
They are usually found in small numbers – rarely more than 100. Most of the time, they feed alone or in loose flocks of up to 60 birds. However, they roost and breed colonially, typically with other heron species.
Unlike the related Black Egret ( E. vinaceigula), the Slaty Egret never feeds by spreading wings over their head to shadow the water below them for better visibility of the fish in the water.
Distribution / Habitat
The largest populations of about 2,000 individuals can be found in the vicinity of the Chobe River and the Panhandle of Okavango Delta (in the village of Shakawe and the Mahango National Park) located in northern Botswana. About 500 – 1,000 birds are estimated to occur at the Liuwa Plain National Park, Kafue Flats and Lake Bangweulu Bangweulu in northeastern Zambia.
Their range extend into northeastern Namibia where about 300 Slaty Egrets live in the Chobe floodplain and Caprivi Strip; through northwestern Zimbabwe (Bangweulu Swamp).
A small number of them may also exist in the Democratic Republic of the Congo and eastern Angola. Their former range also included northern South Africa. Unconfirmed records exist from Mozambique (Zambezi Delta), Angola and possibly Malawi.
Slaty Egrets are mostly sedentary (non-migratory); except for some movement in response to rains and availability of food. Their movements are poorly understood at this point in time.
The Slaty Egrets inhabit river floodplains, freshwater marshes and temporary shallow wetlands.
They prefer areas where water levels are receding and tend to avoid open water. They are most often found in areas with a generous cover of short, emergent vegetation.
They feed in shallow waters and breed in temporary wetlands at the time of maximum water levels.
Their numbers have been declining attributed for the most part to habitat conversion and degradation, and human disturbance. The world population is estimated to consist of around 3,000 – 5,000 individuals (the former estimate, in 1985, listed about 5,000 – 10,000). They are classified as Vulnerable and are protected under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA).
The Slaty Egrets measure about 24 inches or 60 cm in length (including the tail). The plumage is mostly blue-grey (sometimes pale grey-grey) in color, but may appear black in low light conditions.
They resemble the more common Black Egret (Egretta ardesiaca) but can be identified by their greenish- yellow legs and the vinous brown throat that extends down right onto the abdomen in juveniles. White markings on the throat and the otherwise dark reddish foreneck are only visible at close range.
Immature birds have a paler plumage and the rufous on the throat extends from throat down the neck.
- The Black Heron (E. ardesiaca) is smaller with only yellow toes (not legs); and lack the reddish foreneck and white throat of the Slaty Egrets.
- They are similar in shape to the Little Egret (E. garzetta), but latter has an all-white plumage.
Breeding / Nesting
Most breeding occurs in temporary wetlands from March to June – coinciding with high flood-levels. They generally breed in small colonies of 1 – 60 nests in beds of Phragmites reeds, as well as on islands of vegetation, such as water figs (Ficus verruculosa), Acacia species and Senegal date (Tsaro) palms (Phoenix reclinata). Their bowl-shaped nests are constructed from sticks and lined with fine plant material. They tend to reuse nests over many seasons.
The average clutch consists of 1 -4 eggs (average being 2.4). The eggs are incubated for 22 – 24 days to hatching.
Diet / Feeding
Slaty Herons typically forage in clear, shallow waters which are less than about 4 inches (10 cm) deep.
Their main prey consists almost exclusively of small, young fish, especially cichlids. In temporary wetlands, they may also feed on frogs, aquatic invertebrates and tadpoles. They also glean snails from lily pads and use “standing flycatching” to capture dragonflies and other insects.
They usually forage in small groups of 4 – 8 individuals.
These egrets do not display the characteristic ‘mantling’ behavior of the Black Egret, which shade the water underneath them with their wings in order to more clearly see the fish swimming in the shallow water.
Alternate (Global) Names
Afrikaans: Rooikeelreier … Chinese: ??? … Czech: Volavka rudohrdlá … Danish: Skifergrå Hejre … Dutch: Sharpe-reiger, Sharpe’s Reiger … Estonian: punakurk-haigur … Finnish: Ruskokurkkuhaikara … French: Aigrette vineuse, Héron à gorge brune … German: Braunkehlreiher … Italian: Egretta ardesia, Garzetta ardesia … Japanese: nodoakakurosagi … Kwangali: Samunkoma … Norwegian: Ruststrupehegre … Polish: czapla lupkowata, czapla ?upkowata … Portuguese: Garça-de-garganta-vermelha … Russian: ?????????? ?????, ????? ??????????????? ??????????, ??????????????? ?????????? ????? … Slovak: volavka bridlicová … Spanish: Garceta Gorgirroja … Swedish: Rödstrupig häger