All previous records of Swierstra’s Francolin were summarised by Mills (2007a), although, due to unclear labelling, there was some uncertainty surrounding the exact details of the skins in the Lubango Bird Skin Collection. The last specimen was collected on 31 August 1971. Besides records from Mount Moco/Soque, the species is known from four specimens from Tundavala, one from Hanha, one from Mombolo and two from Cariango (see Mills 2007 for details on localities). In January 2009 Michael Mills searched extensively for the species in suitable habitat in the vicinity of Tundavala/Lubango (14.917 ˚ S, 13.501 ˚ E). No birds were found, despite knowledge of the species’ calls, and playback being used to stimulate calling, in order to increase rate and reliability of detection (Boscolo et al. 2006).

All our records from the three field visits to Mount Moco (of at least 18 different groups) come from forest, forest edge or rank growth in gullies, with only one pair venturing marginally into the adjacent rank grassland. Birds were vocal each morning in July and August, but were heard only once in November 2008. Playback experiments using Mills (2007b) and much-improved newer recordings (Mills, in prep.) did elicit vocal responses in July/August, although not always. The most extensive surveys were made in 2009, when 16 pairs were found in 4 days. In November, flowing forest streams made it impossible to hear francolin walking in the leaf litter, but in July/August, when most of the rivers were dry, birds were often detected by hearing them walk across the dry leaf litter. In July/August, time of day and weather conditions also strongly influenced ability to detect birds. Birds typically called from sunrise to 10:00, after which they became silent and could not be stimulated to crow, and again at sunset. Birds either did not call, or could not be heard, during windy conditions. Conditions (time to walk to and between forest patches, and weather) and time available made it impossible to survey all forest patches before 10:00. Hence, density estimates are only reliable for some patches, surveyed during optimal times.

Most forest patches smaller than 1 ha were not found to hold any francolin, although one patch of 0.5 ha had one group. In one forest patch of 6.7 ha, seven pairs of Swierstra’s Francolin were found during extensive surveys during optimal conditions, and in a patch of 18.7 ha of forest, 4 groups were found in the upper 25% of the forest. These data suggest that Swierstra’s Francolin occurs at a maximum density of c. 1 group/pair per hectare in forest patches larger than 1 ha. Based on these data, we estimate a total maximum population of 80 pairs of Swierstra’s Francolin at Mount Moco.