. Bulletin of the British Ornithologists' Club. . Fig. 3 Underside of wings showing reduced chestnut colouration, (top) Metriopelia aymara. (bottom) Petrophassa rufipennis. of chestnut colour, while G. s. striata shows it reduced to a trace on the edge of the primaries and G. s. placidus shows none. There is a noticeable amount of white on the inner web of the primaries of the last species, although this is not so clearly demarcated and obviously homologous with the chestnut colouration as it is in the case of Petrophassa aJbipennis. In Africa the chestnut colouration is found in a number of s
. Bulletin of the British Ornithologists' Club. . Fig. 3 Underside of wings showing reduced chestnut colouration, (top) Metriopelia aymara. (bottom) Petrophassa rufipennis. of chestnut colour, while G. s. striata shows it reduced to a trace on the edge of the primaries and G. s. placidus shows none. There is a noticeable amount of white on the inner web of the primaries of the last species, although this is not so clearly demarcated and obviously homologous with the chestnut colouration as it is in the case of Petrophassa aJbipennis. In Africa the chestnut colouration is found in a number of small doves— Oena capensis, Tutrur tympanistria, T. afra, T. abyssinica, T. chalcospilos, and T. brehmari. In America the species concerned are mostly neotropical, but two species, Scardafella inca and Columbina passerina extend into the southern parts of North America. The chestnut colouration is found in Scardafella inca and S. squammata. It is present in Columbina passerina and in C. talpacoti rufipennis, but absent in C. t. talpacoti. Metriopelia aymara is peculiar in that it shows a small and distinct area of chestnut towards the base of the primaries (Fig. 3), while there is none in the other species of Metriopelia. The Function of the Colour. It is difficult to assign an immediate and obvious function to this colouration. The disposition of the colour on the primary feathers is such that it is not normally visible when the wing is closed. It appears as a sudden patch of colour when the bird flies, and this effect is heightened in some species by the presence of more extensive chestnut colouration on other parts of the underwing, or by contrasting areas of black or white on the upper or lower surface of the wing bordering the primaries. Such colouring obviously has some signal or startle function. Unlike other conspicuously coloured parts of the plumage it does not appear to play an obvious part in epigamic displays. There are not many common factors of behaviour that li
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