Red-knobbed Coot

POPULATION & DEMOGRAPHY: Common. In s and e Africa combined, est 100 000-1 000 000, with marked fluctuations in numbers according to environmental conditions³⁹. In s Mozambique, est > 10 000 at times²⁴. Oldest ringed bird 23 yr 9 mo and 18 yr³⁹. Prey of Tawny Eagle³³, African Fish-Eagle^17,33,41,50, Verreauxs' Eagle-Owl⁷ and Nile Crocodile Crocodylus niloticus²³. Other causes of mortality incl botulism^2,45. Ectoparasites incl ticks Rhipicephalus tricuspis³⁷ and bird lice Laemobothrion atrum²⁰. Collides with buildings, fences and overhead wires, and occasional road casualty²⁵.

MOVEMENTS: Part of population resident and sedentary, but most nomadic, moving in response to rainfall³⁹. Permanent waters provide refuges during years of low rainfall²⁸. However, numbers fluctuate continually, regardless of rainfall, indicating movement even in dry years²⁸. 26 023 ringed by 1998, mostly at Barberspan NR, NW Province, and Rondevlei NR, sw W Cape³⁹. Most movements from Barberspan to south-west and south-east²⁷, but at least 2 records of movements across Kalahari Basin; also 1 to s Mozambique³⁹, 1 to sw Zambia⁴⁰. Greatest distances moved from Barberspan were by birds ringed Jan-Apr, when water levels highest²⁷. Birds probably move at this time to ephemeral wetlands, returning to more permanent waters as former start to dry out³⁹. No recorded movements between Rondevlei and Barberspan, but 1 ringed at Rondevlei moved 1 215 km north-east to Mooi R, KwaZulu-Natal³⁹. Of the remainder of the (1 232) recoveries, only 11 birds moved > 200 km (all from Barberspan), being recovered 243-1 078 km away³⁹.

HABITAT: Open, small to large freshwater ponds, lakes, dams, vleis, temporary pans, flood plains, swamps with reeds (Phragmites spp), Bulrushes Typha capensis and Papyrus Cyperus papyrus, sewage ponds, and occasionally on rivers and tidal lagoons⁴⁰, favouring wetlands with emergent vegetation and pondweeds (Potamogeton spp)¹⁸, especially when br³⁶. Occurs on more open waters when not br³⁶. During flightless moult, on more permanent waters with submerged aquatic plants and fringing emergent vegetation that provides cover⁹.

Author:WRJ Dean