The breeding biology and ecology of the White-necked Picathartes Picathartes gymnocephalus temminck 1825, in Sierra Leone

Thompson, Hazell Shokellu (1998). The breeding biology and ecology of the White-necked Picathartes Picathartes gymnocephalus temminck 1825, in Sierra Leone. PhD thesis The Open University.



This thesis investigates the ecology, taxonomic affinities and conservation management in Sierra Leone of a threatened West African forest bird, the White-necked Picathartes Picathartes gymnocephalus, which has not been previously studied in detail.

The incubation and nestling periods (20 and 25 days) respectively were longer than is usual for most tropical passerines. In most cases, one clutch of two eggs was laid between June and December, immediately followed by moult between January and May (the dry season). Peaks in egg laying occurred 1-2 months after the maximum monthly rainfall. Both parents cared for the young and fed nestlings disproportionately more earthworms, frogs, millipedes and earwigs in relation to their abundance in the environment. Nestlings fledged when still as much as 30% below adult size.

Food abundance peaked in both forest and farmbush (forest regrowth) habitat at the start of the wet season and in the early part of the dry season; coinciding with the period immediately prior to egg-laying and with dispersing fledglings respectively. Potential Picathartes prey were more abundant in farmbush than forest habitat.

The proportion of eggs laid that resulted in fledged young was 22.9% and productivity was 0.22 chicks per adult. Nest predation was the main cause of nest failure but infanticidal behaviour played a significant role. A substantial number of non-breeding birds were apparently present in populations and infanticidal behaviour may have been a consequence of competition for limited nest sites.

Population density was estimated as 0.37 individuals km-' and the total population in Sierra Leone as about 1100. Local populations in forest reserves are close to the theoretical minimum for long-term viability in all cases but populations are apparently stable or declining only very slowly. Abandonment of colonies was associated with habitat degradation but there was also evidence that Picathartes may be fairly tolerant to disturbance in some areas. Phylogenetic analysis using mitochondrial DNA of the cytochrome b gene suggests that Picathartes is more closely related to the thrush-babbler assemblage than the crows.

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