Showing papers on "Biodiversity published in 1975"

The Ecology of Fruit Pigeons in Tropical Northern Queensland.

Abstract: Seven species of fruit pigeon were studied during 3 years in the lowland tropical forest of N. Queensland to find the effect of forest species on pigeon populations and breeding habits and the basis for coexistence of 7 species. Because of the variety of plant species and the differences in their fruiting seasons, fruit was available all the year round and the diet of each species changed according to the fruit available and the selectivity of their feeding habits; none of the species studied ate anything other than fruits or seeds, the latter representing an appreciable fraction (20%) only in the brown pigeon. The foraging habits of all species were recorded and their relative abundance was assessed. Pigeons were most numerous during the dry season, which was also the breeding season. Each species selected a different range of fruiting plants owing to nomadism and migration. At any one time 2 or 3 pigeon species were common, while the rest were rare or absent. The plant family Lauraceae was of major importance. It is suggested that the many species (2250 in all) in this family have developed collaterally with the fruit-eating birds of appropriate feeding habits.

Plant communities on permanent plots of the serengeti plains

Abstract: During 1972 the vegetation mosaic within five plots located representatively within the Serengeti Plains (Serengeti National Park, Tanzania) was described by the Z:urich-Montpellier method and mapped with the aid of aerial photographs. Two plots, in the northwestern Serengeti Plains, belong to thePennisetum mezianum-grassland type. The vegetation mosaic of these plots (comprising four and five vegetation units respectively) is marked by rapid changes over short distances in species composition, height and degree of cover of the herb layer. Two plots in the central Serengeti Plains are dominated by a low dense cover ofAndropogon greenwayi-grassland. These plots show heterogeneity in soil conditions and a marked vegetation mosaic comprising three and four vegetation units respectively on the basis of varying responses of the leading species. One plot in the southeastern Serengeti Plains, which is dominated bySporobolus verdcourtii-grassland, is relatively homogenous. Only two vegetation units were distinguished here. Chemical analysis shows that soil factors influence the occurrence of vegetation zones over large areas as well as the pattern of the vegetation mosaic within the relatively small study plots. The Serengeti Plains are characterized by a northwest-southwest gradient of environmental factors which control soil conditions. High rainfall and thin deposits of volcanic tuffs influence soil characteristics which supportPennisetum mezianum-grassland. The soil ofSporobolus verdcourtii-grassland, however, is influenced by low rainfall and thick deposits of volcanic tuffs which have high levels of salinity and alkalinity. These broadly defined site conditions show correspondingly different levels of carbon and nitrogen. The influence of these two chemical factors is also reflected in the nature of vegetation mosaic within each study plot. It is possible to ecologically classify the plant species into six groups based on nutrient requirement levels. These groups can be used as indicators for nutrient supply as well as for general chemical conditions of the soils of the plant communities which were studied.

Observations on the Breeding Biology of some New Guinea Murid Rodents

Abstract: Breeding records are given for 10 murine rodents from the Eastern Highlands District of Papua New Guinea. Reduced breeding activity through the dry season is apparent for Rattus exulans, R. ruber and Melomys rufescens, with a cessation of breeding at this time in R. niobe, R. verecundus, M. levipes, M. rubex, Pogonomys sylvestris, P. mollipilosus and probably Pogonomelomys sevia. Available evidence suggests that M. rubex varies in reproductive performance between years. Mean litter size is low in all species with mean live embryo counts from 3·09 in R. exulans to 1·09 in M. levipes and 0·75 in P. sevia. Pregnancy concurrent with lactation appears to be frequent in M. rufescens and perhaps P. sevia, and was noted on occasion in R. exulans, R. verecundus and M. levipes.

The naturalized and cultivated exotic Acacia species in South Africa

Abstract: The first species of Acacia from Australia are thought to have been brought to the Cape in 1845. Some of the factors which are believed to have contributed to the success of the exotic Acacia species are enumerated briefly. A key to the identification of the naturalized Acacia species is provided, together with descriptions of each species and an indication of their range of distribution in our area.

Highland vegetation in south-eastern nigeria and its affinities*

Abstract: The environmental conditions and vegetation associated with high elevations in south-eastern Nigeria are described. The forest flora is the richest and very diverse, many families in it being represented by small numbers of species. In the grassland flora the majority of species belong to a few well-represented families. The transition zone vegetation is poorest in species but in other respects intermediate between the forest and the grassland.

Food of the Plumed Pigeons, Geophaps Plumifera and G. Ferruginea.

Abstract: The plumed pigeon, Geophaps plumifera, and the red plumed pigeon, G. ferruginea, are among the few birds that can live permanently in the arid spinifex grasslands of central, northern and western Australia. They are not found in sandy deserts and are most characteristic of hilly or mountainous places. They are strongly associated with spinifex, though not confined to it. The contents of the crops were analysed for 564 and 386 birds of the two species obtained over a wide area of Northern Territory and Western Australia. Food was almost entirely the seeds of drought-resistant grasses and herbs; animal and vegetative plant material occurred only in traces. Water derived from the food can have little value in body processes. Although the birds are closely associated with the spinifex grasses Triodia and Plectrachne, those were not important sources of food; in one area only was the seed eaten and it then provided about one-quarter of the annual food. Other aspects of the spinifex grassland appear to be more important in determining the birds' distribution than the food value of the spinifex.