Preferred habitat of white-browed sparrow-weavers Plocepasser mahali

Habitat use by white-browed sparrow-weavers Plocepasser mahaliwas studied in the Bloemhof area, South Africa. The habitat of nine sparrow-weaver groups consisted of three vegetation communities: Acacia erioloba community, Nidorella resedifoliacommunity and Conyza bonariensis community. The latter community comprised disturbed, ecotonal areas along the edges of roads and maize lands and had a lower basal cover and higher terrestrial arthropod availability than the other two plant communities. The Conyza bonariensis community, together with areas with little vegetation cover, was well used by sparrow-weavers. Seeds eaten by sparrow-weavers also reflect the open character of feeding areas. Termites are an important sparrow-weaver food taxon and large similarities between the geographical distributions of Trinervitermes trinervoides and sparrow-weavers exist

The importance of low host densities for successful parasitism of diederik cuckoos on red bishop birds

Parasitism by diederik cuckoos Chrysococcyx caprius on their main southern African host, the red bishop bird Euplectes orix, was studied. Virtually all the cases of parasitism occurred where there were low densities of red bishop nests. Data from the present study were combined with published observations to show that the incidence of parasitism is much higher in small breeding colonies of red bishops than in large colonies. Aggression of red bishops towards diederiks is described. I suggest that diederik cuckoos cannot approach red bishop nests undetected where large concentrations of red bishops are found. High levels of brood failure in small red bishop colonies caused by brood parasitism may constitute a selective force for colonial breeding in this host species

Relationship between body temperature and air temperature in stridulating male crickets, Gryllus bimaculatus (Orthoptera: Gryllidae)

Body temperatures of singing male Gryllus bimaculatus were measured for the first time. Body temperatures were strongly correlated with ambient temperature. This indicates that, unlike some other orthopterans, larger crickets are not dependent on an elevated body temperature for efficient calling. Our results confirm that it is reasonable to use ambient temperature as an approximation of body temperature in behavioural and bio- acoustic studies

Book Reviews

Book Review 1Book Title: Atlas of Microscopic Structures of Fur Skins Vol. 1Book Authors: Anton Blažej et al.Elsevier Amsterdam and SNTl, Prague, 1989. 378 pages.Book Review 2Book Title: Ornithology for AfricaBook Author: Gordon L. MacleanUniversity of Natal Press, 1990. 270 pages.Book Review 3Book Title: Biology of the Vespine WaspsBook Authors: Makoto Matsuura & Seiki YamaneSpringer-Verlag, Berlin, 1990. 323 pages, numerous figures, tables and photographs. ISBN 3-540-51900-9Book Review 4Book Title: Horns, Pronghorns, and AntlersBook Authors: Edited by G.A. Bubenik & A.B. BubenikSpringer-Verlag, New York. ISBN 0-387-97176-9. 562 pp.Book Review 5Book Title: Ecophysiology of Desert Arthropods and ReptilesBook Author: J.L. Cloudsley-ThompsonSpringer-Verlag, 1991. 203 pagesBook Review 6Book Title: Practical Taxonomic ComputingBook Author: Richard J. PankhurstCambridge University Press. 202 page

Dietary overlap in plocepasserine weavers (Aves: Ploceidae)

The food taken by the closely related white-browed sparrow-weavers Plocepasser mahali and sociable weavers Philetairus socius includes both plant material and insects. An analysis placing food items into taxonomic categories indicates that the important food sources of both species are identical. Seasonal utilization of different food taxa was also similar between the two species. These similarities are interpreted in an evolutionary perspective

Geographic variation in social behaviour of white-browed sparrow-weavers, Plocepasser mahali

White-browed sparrow-weavers are social birds occurring in the semi-arid parts of Africa. Large variations in the density (abundance) of these birds in different parts of the continent probably result from differences in food supply, and are correlated with differences in vegetation and rainfall. Despite these local differences in environment, the social system of the species is surprisingly uniform: group size varies by a factor of less than two, and the presence of helpers within groups has been recorded at all the study sites. This contrasts with the published data for a number of other social vertebrates. The selective force shaping sparrow-weaver sociality may be constant throughout the geographic distribution of these birds. If so, this selective factor is not related to food supply, but probably to a high mortality rate

Social interactions of black-backed jackals <i>canis mesomelas</i> in the Kalahari Gemsbok National Park

Social interactions among black-backed jackals are recognised as amicable, agonistic and aggressive. Allogrooming within a jackal pair is common, and a fixed "greeting" ceremony takes place between the pair members. Agonistic postures are well-developed, and closely follow the typical canine pattern, with minor characteristics specific to black-backed jackals. A behaviour pattern which is apparently rare in canines, is described - the submissive animal rests its forelegs on the rump of the dominant. Body-slamming is common. Occasionally submissive animals hide in order to avoid interactions with dominant ones. Submission is not stereo-typed, but is graded into a number of steps. It would appear that the intensity of submissive postures is at least in part determined bv the degree of dominance of the superior animal Black-backed jackals have a well-developed social life

Preliminary comparison of calls of the hybridizing fur seals Arctocephalus tropicalis and A. gazella

The Antarctic fur seal (Arctocephalus gazella) and the Subantarctic fur seal (A. tropicalis) hybridize on a relatively small scale at Marion Island. To date the description of calls published for A. tropicalis and A. gazella are fragmented and not easily compared.We compare the vocal signalling of males and females of the two species of fur seals to aid understanding of the factors involved in hybridization. Five call types were compared: barking, guttural challenges and territorial calls emitted by adult males; the pup attraction call used by adult females and the response: female attraction call emitted by pups. The calls emitted by males of the two species have certain similarities but are separated by multivariate analyses. By contrast, the calls of females and pups of the two species are more similar and do not cluster separately. Since many of the differences in male calls are audible to the human ear, female seals can presumably also hear these differences and we suggest that interbreeding of the two fur seal taxa is not caused by similarity in male vocal communication. Following this preliminary study, further behavioural studies are required for a fuller understanding of hybridization in these animals.Key words: fur seals, sound communication, mate recognition, systematics, Marion Island