Behaviour This species is considered mostly sedentary, but can move seasonally within wetlands across its range, apparently in response to rains which cause seasonal variation in habitat conditions (Hancock et al. 2006a, Tyler 2005, Tyler 2024). However these 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 DR Congo, Zimbabwe, Mozambique and South Africa indicate that the species has a tendency to vagrancy (del Hoyo et al. 1992, Kushlan and Hancock 2005). 
Breeding 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). 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. 2006, Reed 2006) and date (tsaro) palms Phoenix reclinata (Atkinson 2003, Hancock et al. 2006).  The nest is a bowl lined with fine plant material (Hancock et al. 2006), usually on a platform constructed from sticks, and the species shows high nest-site fidelity (Hancock et al. 2006). Clutch size has been recorded as 1-4 eggs, with a mean of 2.4 (n = 16) (Hancock et al. 2006, 2006), and the incubation period in one nest was recorded as 22-24 days (Hancock 2006).
Habitat It inhabits river floodplains, marshes, and temporary shallow vegetated 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). It forages in water less than 10 cm in depth (Kushlan and Hancock 2005), and can favour the edges of large mammal tracks, such as Hippopotamus Hippopotamus amphibius or Elephants Loxodonta africana and it often occurs in association with Red Lechwe Kobus leche (Hancock et al. 2006a). 
The area and quality of the species' habitat is inferred to be declining due to the impact of several threats, notably conversion to agriculture (Tyler 2012); dam construction (Tyler 2005, Kushlan and Hancock 2005); and the destruction of breeding sites by fire (Tyler 2024) and through the increasing abundance of large herbivores (Hancock et al. 2006a). 
Diet When possible it feeds mainly on young fish (Dowsett 1981, Mathews and McQuaid 1983), especially cichlids (Hancock 2006c), amphibians and aquatic invertebrates (Mathews and McQuaid 1983, Kushlan and Hancock 2005, Tyler 2005, Hancock 2006a, 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). Invasive plants may affect foraging efficiency and consequently reduce foraging habitat, while the impact of invasive invertebrates may reduce fish populations (Hancock et al. 2006a, Tyler 2012, Tyler 2024), which could affect the species' reproductive success.

This species mainly occurs in northern Botswana, mostly around the Okavango Delta and Linyanti/Chobe river system (Tyler 2012, Tyler 2024), where breeding occurs in at least 12 heronries [S. Tyler in litt. 2012]). Also breeds in countries adjacent to the populations in the Okavango Delta; southern Zambia, Namibia, and perhaps also Angola and Zimbabwe (Tyler 2024).

The species wanders more widely when not breeding and is known as a regular and, since c. 2018, increasing but still peripheral visitor to South Africa (D. Harebottle in litt. 2024, Tyler 2024). There is a record of the species breeding following exceptional rains, but the attempt failed and has not been repeated (Tarboton 1996, Tyler 2024). It is widely recorded in Zambia, notably in the Barotse Floodplains, including Liuwa Plain and in the Kafue Flats (Tyler 2024). The species was apparently formerly frequent in the Bangweulu Swamp but there are few recent records (Tyler 2012, Tyler 2024). In Botswana it is also recorded in other areas, such as the Thamalakane and Boteti Rivers, and near Lake Ngami (Tyler 2024). Records from northern Namibia, including Etosha National Park, along the Chobe floodplain, the Caprivi Strip and Tsumkwe District, are assumed to be non-breeding individuals dispersing from the Okavango Delta (Tyler 2024). In Zimbabwe few have been recorded away from the likely breeding areas along the Zambezi (Tyler 2024).

Its occurrence in Malawi and Mozambique is uncertain (Parker 2005, Tyler 2024). In the latter there have been repeated reports of presence, but without documented records until photographic confirmation of a single bird in 2023 in the Zambezi Delta (Tyler 2024). Seasonal occurrence here remains uncertain as this may be a vagrant individual or there may indeed be a population present given the difficulty in detecting the species from aerial surveys (Tyler 2024). While the species likely does occur at least occasionally in Malawi, there do not appear to be any confirmed records (Tyler 2024).

Records of individuals in Katanga in the Democratic Republic of Congo and Cape Town, South Africa show the species is capable of significant long-distance movement (Tyler 2024, eBird 2025).

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, Tyler 2024), although these 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), and although regular waterbird counts do occur in Namibia, Zambia and Zimbabwe, there has been a lack of volunteers available to carry out transect surveys in Botswana (Tyler 2024). Experts and organisations are assisting in the recording of the species in Zambia and Angola (Tyler 2024). An International Species Action Plan was produced in 2012 (Tyler 2012), based upon which an Implementation Plan is currently being developed (D. Harebottle in litt. 2024), and information collected on the species in Botswana at the time was also incorporated into the management plan for the Okavango Delta (Hancock 2006c). An International Slaty Egret Working Group is also currently being established (D. Harebottle in litt. 2024).

Conservation Actions Proposed
Monitor the species' population size and trend, including by surveying along fixed transects and organising coordinated roost counts (Hancock et al. 2006a, Tyler 2024). Conduct further baseline surveys and ecological studies to improve knowledge on and 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 2012). Implement surveys to identify all breeding colonies in Botswana and possibly in Zimbabwe and Zambia, and key non-breeding sites in all range states (Tyler 2012). Initiate a study to determine movements of Slaty Egrets between range states using radio transmitters on nestlings or full-grown birds (Tyler 2012). 
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 2012). 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. Conduct research into the importance of burning, and grazing by Red Lechwe Kobus leche and Hippopotamus Hippopotamus amphibius to the suitability of habitat for the species (Hancock et al. 2006a). Incorporate concerns over the damage of nesting sites by Elephants Loxodonta africana into Elephant management plans (Hancock et al. 2006a). Control the spread of Salvinia 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 2012), including through liaising with the Fisheries Department and the monitoring and impacts of the Redclaw Crayfish (Tyler 2024). Continue investigating the effects of Deltamethrin on the availability of prey species (Tyler 2024). 
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). Protect breeding sites, and, if possible and necessary, construct firebreaks around breeding sites (Hancock et al. 2006a, Tyler 2024). 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). Prevent or control development that would reduce the species’ breeding habitat, including the implementation of EIA studies before any development (Tyler 2021). Establish an official Slaty Egret Working Group (Tyler 2012), to help continue ongoing and establish future conservation actions. Research funding opportunities to carry out conservation actions.