Data Zone
Justification of Red List category
This species is classified as Vulnerable because it has a small and declining population. Apparently suitable habitat is widely available throughout its range, yet it is never common, thus its rarity remains unexplained.
Population justification
A population estimate of 3,000-5,000 individuals follows new surveys and replaces Collar and Stuart's (1985) estimate of 5,000-10,000 individuals. This roughly equates to 2,500-3,300 mature individuals.
Trend justification
The population is suspected to be in decline owing to the effects of habitat conversion and degradation, and human disturbance. The likely rate of decline, however, has not been estimated.
Egretta vinaceigula occurs in Zambia (perhaps 500-1,000 birds, notably at Liuwa Plain, and Kafue Flats in some years, although breeding not recorded [R. J. Dowsett in litt. 1999, 2000, P. Leonard in litt. 1999]), northern Botswana (probably over 2,000 birds [S. J. Tyler in litt. 2007], mostly around the Okavango Delta and Chobe river, where breeding occurs in at least 12 heronries [S. Tyler in litt. 2012]), and northern Namibia (c.300 birds [R.E. Simmons and C. Brown per Hancock et al. 2006a], especially along the Chobe floodplain and Caprivi Strip). It wanders more widely when not breeding (M. Herremans in litt. 1999), and possibly occurs sparsely in Katanga in the Democratic Republic of Congo, in Zimbabwe, and occasionally South Africa. It is expected to occur in Mozambique (its presence on the Zambezi Delta is unconfirmed [Parker 2005]), Angola and possibly Malawi. The species is nearly always encountered in small numbers, e.g. rarely more than c.100 together in Zambia (R. J. Dowsett in litt. 1999, 2000), and it is likely that the Okavango Delta/Lake Ngami population is in excess of 2,000-3,000 birds, with a world population of c.3,000-5,000 birds (R. J. Dowsett in litt. 1999, 2000, Tyler 2012).
Behaviour This species is mostly sedentary (del Hoyo et al. 1992), but moves seasonally within wetlands, apparently in response to rains (Hancock et al. 2006a), which cause seasonal variation in habitat conditions (Tyler 2005). However the movements are in general poorly understood. It occurs year-round in some areas (such as Zambia) where it is not known to breed (Tyler 2005, Kushlan and Hancock 2005). Occasional records from Malawi, Zimbabwe, Mozambique and South Africa indicate that the species has a tendency to vagrancy (del Hoyo et al. 1992, Kushlan and Hancock 2005). Breeding appears to be irregular, but most often occurs during the months of March-June, coinciding with high flood-levels (Randall and Herremans 1994, Harrison et al. 1997, S. J. Tyler in litt. 2007). It breeds in small colonies of 1-60 nests, and usually forages in small groups of 4-8 individuals (Hancock and Kushlan 1984), although it may forage solitarily or occasionally in larger aggregations of up to 60 individuals (Kushlan and Hancock 2005, Tyler 2005). Habitat It inhabits river floodplains, marshes, and temporary shallow wetlands, preferring areas where water levels are receding from their seasonal peak (Hancock et al. 1978, Hancock and Kushlan 1984, Kushlan and Hancock 2005). It tends to avoid open water (Kushlan and Hancock 2005), being most often found in areas where there is ample cover of short, emergent vegetation (Dowsett 1981, Martínez-Vilalta and Motis 1992) such as Cynodon dactylon and Panicum repens (Hancock et al. 2006a). The availability of this habitat is increased by fire and high grazing pressure, however there has so far been insufficient data to confirm important links between these factors and the species's abundance, although it has been observed to be more abundant on burnt floodplains, and it often occurs in association with Red Lechwe Kobus leche (Hancock et al. 2006a). It forages in water less than 10 cm in depth (Kushlan and Hancock 2005). Breeding It breeds in temporary wetlands at the time of - or shortly after - maximum water levels (Kushlan and Hancock 2005). Its preferred breeding habitat is Phragmites reedbed (Hancock et al. 2006a), but it will also nest on islands of vegetation such as water figs Ficus verruculosa, Acacia spp. (Hancock et al. 2006a, Reed 2006) and date (tsaro) palms Phoenix reclinata (Atkinson 2003, Hancock et al. 2006b). Diet When possible it feeds mainly on young fish (Dowsett 1981, Mathews and McQuaid 1983), especially cichlids (Hancock 2006c), but in temporary wetlands where fish do not occur, its diet consists of frogs, aquatic invertebrates (Hancock et al. 2006a, 2006c) and tadpoles (Mathews and McQuaid 1983, Kushlan and Hancock 2005, Tyler 2005, Hancock 2006c). It locates prey by sight in clear, shallow water (Hancock et al. 2006a, 2006c). Additionally it will glean snails from lily pads and uses standing flycatching to catch dragonflies and other insects (Mathews and McQuaid 1983, Kushlan and Hancock 2005). It forages diurnally, often in association with other heron and wader species (Kushlan and Hancock 2005). Breeding Site The nest is a bowl lined with fine plant material (Hancock et al. 2006b), usually on a platform constructed from sticks, and the species shows high nest-site fidelity (Hancock et al. 2006a). Clutch size has been recorded as 1-4 eggs, with a mean of 2.4 (n = 16) (Hancock et al. 2006a, 2006b), and the incubation period in one nest was recorded as 22-24 days (Hancock 2006a).
The wetlands inhabited by this species face many threats, including flood regulation (P. Leonard in litt. 1999), water abstraction, land-claim for agriculture (S. J. Tyler in litt. 1999), reed-cutting (through disturbance and burning) (Hancock et al. 2006a), fire (Randall and Herremans 1994), rice production and disturbance from tourists (Hancock et al. 2006a). It is known to have disappeared from part of the Kafue Flats due to flood control by humans, which involved damming the Kafue River (Tyler 2005, Kushlan and Hancock 2005). At the Okavango Delta (Botswana) food availability appears to be limited and any decrease would impact the survival of adult and immature birds (Hancock et al. 2006a). The aerial spraying of Deltamethrin to eradicate tsetse flies has not had any discernible impact on populations as yet (Hancock 2008), despite being known to affect small fish and aquatic invertebrates (Hancock 2006b). The presence of Salvinia molesta in some areas reduces visibility by covering the water surface and probably affects foraging by the species (Hancock et al. 2006a). Breeding success is erratic, and can be significantly affected by human interference, poor floods and predation of nests and adults (Martínez-Vilalta and Motis 1992, Randall and Herremans 1994, R. E. Simmons in litt. 1999). In Botswana, two major historical breeding sites in reedbeds have been destroyed by human-induced fire and their regeneration prevented by decreased flood levels, whilst other sites have suffered human disturbance (Hancock et al. 2006a). Feeding and trampling by elephants Loxodonta africana, which have expanded their range since the moratorium on elephant hunting, and to a lesser extent buffalo Syncerus caffer, renders reedbeds and trees unsuitable for nesting (Hancock et al. 2006a). Productivity may be limited by high levels of predation by raptors and other species at some colonies (Hancock et al. 2006a). The species may also be threatened by climate change in the long term (Hancock et al. 2006a).
Conservation Actions Underway
CMS Appendix II. The main populations in Zambia and Botswana occur within protected areas (C. Brewster in litt. 1999, M. Herremans in litt. 1999, S. J. Tyler in litt. 1999, T. Dodman in litt. 2000), although these latter do not necessarily protect against catchment-wide threats to wetlands (R. J. Dowsett in litt. 1999, 2000). The species is the subject of long-term studies and monitoring in Botswana (Hancock et al. 2006a, 2006b), though the biennial African Waterbird Census does not incorporate any suitable habitat for the species (Hancock 2008). Transect routes for long-term monitoring have been identified though no visits occurred in 2008 (Hancock 2008). An International Species Action Plan was produced in 2012 (Tyler 2012). Information recently collected on the species in Botswana is to be incorporated into the Slaty Egret Action Plan (Hancock 2008) and the management plan for the Okavango Delta (Hancock 2006c).
60 cm. Small, dark egret. Adult appears blue-grey, sometimes pale blue-grey, but may appear black in poor light. White throat and dark reddish foreneck only visible at close range. Legs and toes greenish-yellow with variable amount of chrome yellow around joints in breeding adults. Juvenile is paler and rufous on throat extends from throat down neck. Similar spp. Shape and feeding behaviour similar to Little Egret E. garzetta, but latter all white. Black Heron E. ardesiaca is smaller, with yellow confined to toes, and lacks reddish foreneck and white throat. E. vinaceigula never feeds by spreading wings over head like E. ardesiaca. Hints Most easily seen in Panhandle of Okavango Delta, at Mahango and Shakawe (Botswana). Feeds singly, but sometimes in loose flocks of up to 60 birds; roosts and breeds colonially, usually with other heron species.
Text account compilers
Ekstrom, J., Evans, M., Khwaja, N., Malpas, L., Martin, R, Pilgrim, J., Shutes, S., Symes, A., Taylor, J., Westrip, J.
Contributors
Brewster, C., Willems, F., Dodman, T., Hancock, P., Simmons, R., Leonard, P., Dowsett, R.J., Herremans, M., Tyler, S.
Recommended citation
BirdLife International (2024) Species factsheet: Slaty Egret Egretta vinaceigula. Downloaded from
https://datazone.birdlife.org/species/factsheet/slaty-egret-egretta-vinaceigula on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.