A NOTE ON THE UNUSUAL CRUSTACEAN COMMUNITY OF A TEMPORARY POOL IN THE NORTHERN CAPE

Summary

A temporary pool in a dry stream bed traversing Grootvloer Pan in the Northern Cape was inhabited by fifteen branchiopod and calanoid copepod crustacean species. There was an unusually high number of congeneric species in the pool; in the class Branchiopoda, five Streptocephalus species and four Daphnia species were collected. In addition, two species of the calanoid genus Metadiaptomus were identified. The high species richness was not related to habitat diversity, pool size or difference in body size of each species. Three species (Streptocephalus purcelli, S. gracilis and Metadiaptomus capensis) had previously been collected only from the winter-rainfall areas of the Cape. Episodic flooding in the Northern Cape in 1988 may have resulted in the unusual community in the Grootvloer temporary pool.     

河北蔚县早更新世哺乳动物化石及其在地层划分上的意义

蔚县东陡壁早更新世哺乳动物化石地点所发现的化石,虽然数量和种类不多,但有一些比较原始的类型。这些第三纪晚期的残留属一直延续生存到第四纪初,并作为第四纪早期哺乳动物群的重要成员。这些新材料的发现,对泥河湾动物群是一个新的补充,并可作为泥河湾地区早更新世地层进一步划分和对比的可靠依据。     

NOTE ON THE NIDIFICATION OF

Palearctic migrant birds are declining, including the Northern Wheatear, and some of the causes of these declines are likely to be operating on their wintering grounds in Africa. We examined seasonal and spatial variation in wintering densities of Northern Wheatears in northern Nigeria, and explored the species’ habitat associations on the wintering grounds to assess the likely effects of habitat change in the Sahel on this species. Densities of Northern Wheatears across northern Nigeria were calculated from point count data gathered during two winters (2000 and 2001) using Distance software, and the relationships between Wheatear presence and habitat variables collected from the same points were explored using general linear models. During mid-winter and early spring, densities of Northern Wheatears peaked, with significantly more birds present in western than eastern study sites. The probability of wheatear occurrence was correlated with Balanites and Salvadora tree density and mean tree height. The Northern Wheatear may benefit from the conversion of woodland habitats in the Sahel to more open savanna. However, sites with very low tree densities showed low probabilities of Northern Wheatears being present, suggesting excessive tree clearance may have a negative effect upon the species.