Breeding behaviour and polygyny in the Red Bishop bird Euplectes orix (L.)

Master Thesis


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University of Cape Town

The red bishop bird, Euplectes orix, is a widespread and locally abundant member of the weaver family, the Ploceidae. It is found over most of Southern Africa, and as, far north as Uganda in the Eastern savannah belt. Large flocks may be found in association with other seedeaters, and the breeding colonies in reeds or tall grass in marshy areas may contain from five to several thousand birds. Recently it has also been recorded as nesting in standing crops in some areas. The adult birds are sparrow-sized, 12-15 cm in length and weighing 20-30 gm. The wing-length in the males ranges from 70-83 mm, and in females from 64-72 mm. Mackworth- Praed and Grant (1962) mention that birds from the Cape are larger, and that there appears to be a decrease in size of birds further north; measurements taken in this study seem to confirm this. During most of the year, both sexes are a mottled light brown colour, with a pale streak above the eye, and the underside pale to almost white, with darker streaks. However, at the beginning of the breeding season the adult males moult into their striking nuptial plumage: the abdomen and face mask are black, while the crown, throat, breast, rump, upper and under tail coverts are scarlet. The mantle feathers are tawny, but the wings and tail remain brown. The bill colour also changes from flesh-coloured to black. Hall and Moreau (1970), whose nomenclature is used for all the passerine species mentioned, regard three species Euplectes orix, franciscus and nigroventris as comprising the "orix superspecies". All three retain the brown wings and tail in the male breeding dress, but show variations in the extent of the red and black plumage. There is no apparent overlap in their ranges, or any evidence of inter-breeding. Two further species, E. hordeceu and E. gierowii, differ in that the wings and tail of the male are also black during the breeding season. Although slightly larger, their plumage is in other respects very similar, and these five species are termed a "species group". There is surprisingly little published information on any of these species. Lack (1935) first described territorial behaviour and polygyny in Euplectes hordeaceus, and later Moreau and Moreau (1938) and Fuggles-Couchman (1942) compared the ecology of E. hordeaceus and E. nigroventris. Skead (1956) produced a valuable basic study of E. orix, and showed it to be polygynous. Emlen (1957) made observations on several Euplectes species in Rhodesia, but the species orix and hordeaceus are confused in his paper, and it is not always clear which he is referring to. Later studies dealing with E. orix by Brooke (1964), Schmidt (1968) and Woodall (1971) are primarily concerned with clutch size, breeding seasons and nesting success, rather than behaviour. However, Crook (1962, 1963, 1964) has produced an important series of papers comprising a comparative study of behaviour in the entire weaver family. He refers mostly to the genus Euplectes, but also quotes observations on individual species, including E. orix. Collias and Collias (1964) have described nest-building behaviour in the weavers, but also mainly at the generic level.