Geophagy in birds of Crater Mountain Wildlife Management Area, Papua New Guinea

Abstract

Numerous New Guinea birds, mostly psittaciforms and columbiforms, have been recorded feeding on soil. This study documents geophagy in the Crater Mountain Wildlife Management Area (CMWMA) in the Eastern Highlands of Papua New Guinea. We present the first documented case of geophagy in the palm cockatoo Probosciger aterrimus and in up to 11 other species. Soil from the site where geophagy by palm cockatoos was recorded was highly weathered and acidic, with a mixture of kaolin, gibbsite, goethite and illite in the clay fraction. Analyses may support the hypothesis that soil is ingested to counterbalance the effects of toxic compounds in fruit. We suggest that the accessibility of the site (an exposed bank), rather than the nature of the soil itself, prompted its use by birds. At another site, a blue-coloured soil on which cassowaries fed was rich in vivianite (an iron phosphate) and contained an iron-rich smectite, and some kaolin and mica in the clay fraction. Why cassowaries feed on this particular soil is unclear, but they may obtain trace elements from it, or take advantage of its high iron or phosphorus content. Obtaining other elements, in particular calcium and sodium, may also be important. Alternatively, there may simply be an attraction to its blue colour, which also attracted the interest of local people and folklore. Birds were also reported to drink salt water within the CMWMA. Taken together, there may be quite different reasons for ingestion of minerals/soils among as many as 23 bird species from five families. © 2005 The Zoological Society of London.