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Egretta vinaceigula

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AVES PELECANIFORMES ARDEIDAE

Scientific Name: Egretta vinaceigula
Species Authority: (Sharpe, 1895)
Common Name(s):
English Slaty Egret
French Aigrette vineuse

Assessment Information [top]

Red List Category & Criteria: Vulnerable C2a(ii) ver 3.1
Year Published: 2013
Date Assessed: 2013-11-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S.
Contributor(s): Brewster, C., Dodman, T., Dowsett, R., Hancock, P., Herremans, M., Leonard, P., Simmons, R. & Tyler, S.
Facilitator/Compiler(s): Ekstrom, J., Evans, M., Malpas, L., Martin, R, Pilgrim, J., Shutes, S., Taylor, J., Symes, A.
Justification:
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.

History:
2012 Vulnerable

Geographic Range [top]

Range Description: Egretta vinaceigula occurs in Zambia (perhaps 500-1,000 birds, notably at Liuwa Plain, Kafue Flats and Bangweulu 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 2011).

Countries:
Native:
Botswana; Mozambique; Namibia; South Africa; Zambia; Zimbabwe
Vagrant:
Malawi
Present - origin uncertain:
Angola (Angola)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: 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.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Behaviour This species is mostly sedentary (del Hoyo et al. 1992), but moves seasonally within wetlands in response to changing water levels, showing movements 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 to 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 (Tyler 2005, Kushlan and Hancock 2005). Habitat It inhabits river floodplains, marshes, and temporary shallow wetlands, preferring areas where water levels are receding from their seasonal peak (Hancock, Elliott and Gillmor 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 10cm 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 species (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 (Hancock 2006c, Tyler 2005Kushlan and Hancock 2005, Mathews and McQuaid 1983). 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).

Systems: Freshwater

Threats [top]

Major Threat(s): 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 did not have 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 [top]

Conservation Actions: Conservation Actions Underway
CMS Appendix II. The main populations in Zambia and Botswana occur within protected areas (C. Brewster in litt. 1999, T. Dodman in litt. 2000, M. Herremans in litt. 1999, S. J. Tyler in litt. 1999), 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). A draft International Species Action Plan to cover the period 2012-2022 was produced in 2011 (Tyler 2011). 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).

Conservation Actions Proposed
Conduct further baseline surveys and ecological studies to clarify the factors affecting its range, population and breeding performance (M. Herremans in litt. 1999, P. Leonard in litt. 1999, S. J. Tyler in litt. 1999, T. Dodman in litt. 2000, Tyler 2011). Implement surveys to identify all breeding colonies in Botswana and possibly in Zimbabwe and Zambia, and key nonbreeding sites in all range states (Tyler 2011). Initiate a study to determine movements of Slaty Egrets between range states using radio transmitters on nestlings or full-grown birds (Tyler 2011). Assign permanent protection to more of the Okavango Delta, especially the northern Panhandle (S. J. Tyler in litt. 1999), and safeguard other key wetlands through designation as reserves or protected areas (Tyler 2011). Enforce legislation and raise public awareness to curb illegal burning of water-margin vegetation and reed-cutting (M. Herremans in litt. 1999). Control disturbance and fires at breeding and roost sites. Monitor population trends by surveying along fixed transects (Hancock et al. 2006a). Conduct research into the importance of burning and grazing by red lechwe and hippos to the suitability of habitat for the species (Hancock et al. 2006a). Carry out studies into whether food is limited at feeding sites and whether this affects survival (Hancock et al. 2006a, Tyler 2011). Control the spread of Salvinia (Hancock et al. 2006a). Increase the awareness of tourists about the impact of disturbance (Hancock et al. 2006a). Encourage tourist guides to adopt a code of conduct for visiting breeding sites (Hancock et al. 2006a). Incorporate concerns over the damage of nesting sites by elephants into elephant management plans (Hancock et al. 2006a). Construct firebreaks around breeding sites (Hancock et al. 2006a). Encourage the transition to modern building materials in local communities (Hancock et al. 2006a). Prevent activities that decrease the area of floodplains, e.g. channel clearing, drainage, large-scale water abstraction, damming and construction of weirs (Hancock et al. 2006a). Investigate the effects of Deltamethrin on the availability of the species's prey. Prevent or control development that would reduce the species’s breeding habitat, including the implementation of EIA studies before any development (Tyler 2011).


Citation: BirdLife International 2013. Egretta vinaceigula. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 December 2014.
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