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White-faced Whistling-Duck Counts Through 2018 Never Regained Lake Manyame’s 1980s Peaks

Group of white-faced whistling-ducks near Victoria Falls, Zimbabwe
Conservation · Population & status

A long-term account published on 15 June 2026 shows that available counts of white-faced whistling-duck (Dendrocygna viduata) at Lake Manyame in Zimbabwe through 2018 never again approached the exceptional totals recorded in the late 1980s. Observers counted 1,565 birds in 1987 and 4,781 in 1988. Across the later series, from 1993 to 2018, the highest reported count was 573 in 2015.

The later series did not show a steady decline

The later counts do not show a simple year-by-year decline. The mean white-faced whistling-duck count was 87.4 during 1993–1999 and 128.3 during 2000–2018, so the later period averaged slightly more birds than the 1990s even though neither period returned to the thousands recorded in the first two surveys. The figures describe counts at one lake, not the size of the wider regional population.

Survey effort complicates the comparison

The authors also identify important limits in the record. The early whole-lake counts involved a large team, whereas later work relied mainly on one family operating from a boat. Some surveys were missed because of unsafe access, fuel shortages or lost data, and mobile waterbirds can shift between wetlands as rainfall and water availability change.

The wider waterbird community at Lake Manyame also changed substantially: the two early surveys averaged roughly 25,600 birds, compared with about 1,500 in the later series, although some of that difference may reflect survey effort. The authors suggest that excessive aquatic vegetation, pollution, overfishing and human disturbance may have contributed to later declines and disappearances and call for renewed surveys of the lake.

Sources and image credit

  1. Rushforth, D., & Marshall, B. (2026). Changes in Waterbird Populations on Lake Manyame. Honeyguide, 72(1), 6–17.Primary article in Honeyguide 72(1), June 2026; BirdLife Zimbabwe posted the issue online on 15 June 2026. It compiles whole-lake counts from 1987–1988 and later counts from 1993–2018, including 1,565 white-faced whistling-ducks in 1987, 4,781 in 1988 and a later maximum of 573 in 2015. The authors discuss survey-effort differences and broader ecosystem pressures.

Image: Bernard Gagnon / Wikimedia Commons — wild white-faced whistling-ducks near Victoria Falls, Zimbabwe, 19 November 2017; group crop for 16:9 display. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 4.0 · Source

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