. Bulletin of the British Ornithologists' Club. M. Louette 210 Figure 1. Central equatorial Africa. The Lower Guinea rainforest block is indicated with oblique barring. considered to be positions taken up after radiation from a refuge and probably still dynamic (Mayr & O'Hara 1986). Suspected present day, as well as past, barriers (except for the presence of a vicariant species) include: degrees of altitude; inimical vegetation surrounding a refuge; savanna; hostile habitat in general: rivers and marsh. Examination of the ranges of such siblings as Estrilda nonnula and E. at
. Bulletin of the British Ornithologists' Club. M. Louette 210 Figure 1. Central equatorial Africa. The Lower Guinea rainforest block is indicated with oblique barring. considered to be positions taken up after radiation from a refuge and probably still dynamic (Mayr & O'Hara 1986). Suspected present day, as well as past, barriers (except for the presence of a vicariant species) include: degrees of altitude; inimical vegetation surrounding a refuge; savanna; hostile habitat in general: rivers and marsh. Examination of the ranges of such siblings as Estrilda nonnula and E. atricapilla allows one to presume that several such factors can act simultaneously (vicariants, philopatry, altitude, non-forest habitat, . .). Competition with other species cannot explain the peculiar distri- butions of the stenotopic forest birds (nor the eurytopic savanna birds mentioned below), because usually no congeneric species are involved. The polyspecific forest genera Bleda and Malimbus (the latter including 2 superspecies) were examined on this account, but no proof of competitive exclusion was found (Louette 1991a). However, the possibility of recent range restrictions or differences in ecological potential between the differ- ent parts of the forest cannot be excluded (Louette 1990). The restricted ranges are situated in particular areas outlined below, for which Louette (1990) produced a list of species {pace that given by Mayr & O'Hara 1986, which contains numerous errors, including the ranges for Glaucidium sjoestedti, Spermophaga poliogenys, Merops breweri, Nectarinia adelberti and others). These restricted ranges cover: 1) the whole of Upper Guinea or Lower Guinea, supporting the strong impact on distribution of the Dahomey gap in western Africa, a present day savanna wedge in the forest (Bates 1931, Moreau 1966); 2) particular parts of Lower Guinea in Cameroon/Gabon, in the Zaire basin proper (only a few), and in a small eastern area;. Please note that t
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