Abstract
The role of bare body parts in sexual signalling in birds has received relatively little attention. I describe how the bare-throated spurfowl males saturate the colours of their throats to attract females. Of the 23 Afrotropical spurfowl species, the bare-throated subgroup includes Yellow-necked Spurfowl (Pternistis leucosceptus), Red-necked Spurfowl (P. afer), Grey-breasted Spurfowl (P. rufopictus) and Swainson's Spurfowl (P. swainsonii). The rest of the species include fully feathered throated spurfowls. Throat colour intensity of bare throats was scored using an extensive online digital photographic archive encompassing the four species across the year's seasons. Each throat (n = 836) was assigned to one of four colour-intensity categories to explore the relationship between colour intensities, breeding cycles, and environmental variation. Except for Swainson's Spurfowl male saturation of throat colours correlated with monthly rainfall, which peaks one or two months before egg laying. Swainson's Spurfowl peaks during egg laying. Yellow-necked Spurfowl has the largest bare throat. Bare-throated spurfowl males perform an elevated courtship display posture above the female to feature their throat colour. No such displays occur in feather-throated spurfowl. Males with low throat colour saturation harbour more ectoparasites on their bare throats than birds with saturated throats. Male Red-necked Spurfowls have significantly larger bare throats than females. The primary function of bare throats probably assists in thermoregulation, particularly in arid regions. The bare throat may have evolved a secondary role in mating. Yellow-necked, Red-necked, and Grey-breasted Spurfowls use their saturated throat colours as ornaments to court females during the breeding season. Unobtrusive female throat colours (unsaturated) may discourage male interlopers and predation during egg laying. Saturation appears to be carotenoid-food based. The different colours among the bare-throated species may serve as prezygotic mechanisms that inhibit cross-breeding and explain why females also have coloured throats.
