Red Bishop Research Articles

Verteilung, lokalisation und absorption der zapfeno¨lkugeln bei vo¨geln (ploceidae)

Evidence is established for the existence of red, yellow and green oil droplets in all parts of the retina including the fovea centralis of some passerine birds ( Euplectes orix, Amadina fasciata, Uraeginthus bengalus, U. angolensis, U. cyanocephalus). The percentage of droplets of those colours were found to be equal for all individuals of one species and independent of differences in sex. For all species tested only in the red field were there small differences in the percentage of the different coloured droplets. Red and yellow drops are only found in single cones, while green drops are found in the chief cones of the double cones. The accessory elements of the double cones have no oil droplets. Investigation of the oil droplets with microspectrophotometer (Zeiss UMSP I) showed that the oil droplets are sharp cut-off filters and that from certain wavelengths on between 70 and 100 per cent of the incoming light is absorbed.

Das Farbunterscheidungsvermögen einiger Ploceidae (Passeriformes, Aves) im kurzwelligen bereich des Spektrums

1. Uraeginthus angolensis (4 birds) and U. bengalus (2 ♂, 2 ♀) were able to distinguish a blue colour (ia 17, Ostwald) from 25 shades of grey. 2. In the blue part of the spectrum (464 nm−493 nm), the birds ( Euplectes orix, 1 ♂; Amadina fasciata 1 ♀; U. angolensis 1 ♂, 1 ♀; U. bengalus 2 ♂, 2 ♀; U. cyanocephalus 1 ♂, 1 ♀) distinguished between several wavelengths identical in intensity and saturation (DIN-system 6164, Muster-Schmidt, Göttingen). 3. The birds were trained to distinguish between a distinct blue colour (18, saturation 3) from another which only was different in intensity. The brighter colour (intensity 1) was positive, the darker (intensity 6) was negative. In the following tests the negative stimulus was shifted toward the brighter color. In these experiments, 5–10 birds were able to discriminate the intensities 1 and 2. 4. When trained to distinguish between different saturation of the same color (18, intensity 3, saturation 1–5) only one bird could discriminate between 5 and 4.

STUDIES OF THE DIEDERIK CUCKOO CHRYSOCOCCYX CAPRIUS IN THE TRANSVAAL

SummaryThe migrant Diederik Cuckoo Chrysococcyx caprius was studied on a 72–acre area near the Klein Jukskei River near Johannesburg from 1955–1958. The birds first arrive in early October, after which the males take up territories and call continually until February; subsequent calls up to April are probably made by young birds.Courtship displays, which involve courtship feeding, and egg‐laying follow the birds' arrival by about a month. The Red Bishop Euplectes orix was the species most commonly parasitized, with smaller equal numbers of Cape Sparrows Passer melanurus and Masked Weavers Ploceus velatus. The cuckoos' eggs differ according to the host species and in two cases hatched between ten and 14 days after laying. The chicks normally evict their hosts' offspring on the second or third day after hatching. The fledging period appears to be roughly 19–20 days, and there is a period of post‐fledging care lasting between 17 and 38 days, during which the chicks are fed different foods by different host species (grass seeds by bishops; insects of different sizes by weavers and sparrows).The fact that the eggs and the calls of the chicks vary according to their host species suggest the existence of three separate host‐specific strains in this area. The incidence of brood parasitism in Red Bishops' nests varied from 7–50% and averaged 25%.

The Comparative Breeding Ecology of Two Species of Euplectes (Bishop Birds) in Usambara

EUPLECTES NIGROVENTRIS CASSIN, the Zanzibar red bishop, and E.h. hordeacea (Linn.), the crimson-crowned bishop, are weavers of the subfamily Ploceinae. On the biology of the former species nothing appears to have been recorded hitherto except the notes reproduced by Reichenow (1904) and those of Vaughan (1929), who (rightly) suspected it to be polygamous. For Euplectes hordeacea we take the work of Lack (1935) as basis and amplify only certain points. Our study is more incomplete than we should have wished because we could not make continuous observations and because of an unexpected technical difficulty. The males of both these bishop birds have a highly conspicuous red breeding dress and are at other times practically indistinguishable in the field from females and young. Both are territory-holding species dependent on grasses for their food and their nesting materials. The architecture of their nests, which are similar except in size, demands close upright vegetation. The rather restricted geographical range of E. nigroventris is wholly contained in that of E. hordeacea. The two species may often be found side by side, but in our experience there is little ecological overlap; the smaller E. nigroventris