The feeding ecology of the African lily trotter Actophilornis africanus (Gmelin) at Lake Naivasha, Kenya


*Kingston Grammar School, Kingston-on-Thames, Surrey, England.


The only feeding habitats available to African lily trotters, Actophilornis africanus (Gmelin), at Lake Naivasha are mats of the alien water fern, Salvinia molesta Mitch. This has replaced the native floating leaved water lily beds. Lily trotters were able to use these mats, taking invertebrate food items from the surface or turning plants over and pecking at the rootlets. Pecking rates and turning rates responded to the nature of the available food, with pecking rates high and turning rates low when terrestrial arthropods were found on the mat surface. Both pecking rates and turning rates were low when large aquatic food items, such as the swamp worm (Alma emeni Michaelsen), were available. Pecking rates and turning rates were both high when the predominant food items were aquatic insect larvae. The largest of these (hydrophilid larvae) were taken in preference to the smaller but commoner chironomid larvae. Colonization of the mats of S. molesta by invertebrates was low if the mats were affected by wind action but higher if they were constrained by enclosure or stranding; mats with higher invertebrate densities supported more feeding lily trotters.