Population Status, Ecology and Conservation Challenges of Cattle Egrets (Bubulcus ibis), Especially in the Southern Africa Subregion: A Systematic Review and Evidence Synthesis.

The Cattle Egret (Bubulcus ibis) is one of Africa's most adaptable yet environmentally sensitive waterbirds, occupying natural wetlands, grazing systems, irrigated agro-mosaics and urban green spaces. We conducted a systematic review of 173 studies published between the 1940s and 2025, incorporating global research where it provided insights relevant to Southern African populations. Using narrative synthesis and quantitative summaries, we evaluated population trends, habitat use, breeding ecology, threats and ecosystem services. Across all studies, habitat and foraging ecology dominated the literature (46.2%), followed by population status and distribution (21.4%), breeding ecology and behaviour (16.8%) and threats and contaminants (15.6%). In Southern Africa, atlas interpretations and site-based surveys from South Africa, Zimbabwe, Botswana, Namibia and Lesotho indicate generally stable or increasing populations over the past three decades, with SABAP-derived occupancy rising from 0.38 (1987-1991) to 0.60 (2007-present). Densities generally peak in irrigated pastures and peri-urban green spaces of eastern South Africa, but remain low in arid Namibia, high-altitude Lesotho and Zambia's under-sampled floodplains. Foraging studies show diets dominated by Orthoptera, enhanced success near livestock and machinery and seasonal shifts in both diet and foraging locations that reflect hydrology-driven changes in prey availability and habitat accessibility. Breeding studies report opportunistic, rainfall-synchronised nesting, mean colony sizes of ~65 nests, clutch sizes of 2.9 eggs and fledging success of ~62%. Key threats include loss of nesting habitat, extreme-weather colony failures, organochlorine contamination and pathogen spillover at poultry interfaces, while ecosystem-service benefits include pest suppression and nutrient redistribution. We recommend three priorities for future research: (1) advanced telemetry and stable-isotope analyses to map movements; (2) routine contaminant and pathogen screening within One Health frameworks; and (3) expanded atlas-based and citizen-science monitoring to address geographic bias. These steps will clarify the species' dual role as a service provider and early-warning indicator of environmental change across Southern Africa.