BIRD POPULATION STUDIES.-V. FIVE CONSECUTIVE DAILY COUNTS OVER 21 ACRES IN NORTHERN RHODESIA

Williams, M.C. &; Nesbit, J.W. 1996. Fatal herpesvirus infection in a Cape Eagle Owl Bubo capensis and a Spotted Eagle Owl Bubo africanus. Ostrich 67:50-62

Fatal, systemic herpesvirus infection was reported in a Cape Eagle Owl Bubo capensis and a Spotted Eagle Owl Bubo africanus. This is believed to be the first report of systemic herpesvirus infections in owls in South Africa. Post mortem examinations revealed multifocal necrosis in the liver and spleen. Histologically, intranuclear inclusion bodies were present, particularly in cells at the periphery of necrotic foci. Typical herpesvirus virions, demonstrable by transmission electron microscopy, were present. Viral isolations were unfortunately not undertaken.     

SOME ASPECTS OF THE DISTRIBUTION OF REACTIVE PHOSPHORUS IN LAKE McILWAINE,RHODESIA: PHOSPHORUS LOADING AND ABIOTIC RESPONSES

SUMMARY

This study was designed to investigate the apparent loss from the water column in Lake McIlwaine This study of significant quantities of reactive phosphorus. The Total Reactive Phosphorus mass-balance for the lake for 1977/78 was calculated, and both in situ and laboratory experiments were carried out to determine the effect of the lake sediments on the phosphorus loading of the lake. The experimental results showed that both uptake and release of phosphorus occurs in the lake, but that uptake of phosphorus by the sediments was by far the dominant process, thus accounting for the observed loss of phosphorus from the water column. The availability of the bound phosphorus for algal growth was also studied and it is suggested that algal uptake of bound phosphorus is possible. Various factors affecting phosphorus uptake by the sediments are discussed.     

2. NOTES ON THE STATUS OF SOME PALAEARC-TIC MIGRANTS IN NORTHERN RHODESIA

Whitfield, A. K. &; Cyrus, D. P. 1978. Feeding succession and zonation of aquatic birds at False Bay, Lake St Lucia. Ostrich 49:8-15.

Seasonal fluctuations in water levels at Lake St Lucia resulted in the inundation of depressions adjacent to the lake. Backwaters formed and were immediately colonized by aquatic invertebrates and fishes. Piscivorous birds dominated the early stages of the backwater feeding aggregations but with the decrease in water levels due to evaporation, crustacean and mollusc feeding birds became abundant. Both piscivorous and invertebrate-feeding wading birds formed a series of overlapping zones parallel to the shoreline.     

THE BREEDING OF THE LESSER FLAMINGO IN THE MWERU WANTIPA, NORTHERN RHODESIA.

A hitherto unreported breeding site of the Lesser Flamingo Phoeniconaias minor is recorded in the Mweru Wantipa or Mweru Marsh, Northern Rhodesia. The site of the nesting colony, its structure, nest construction and behaviour of the birds is described. The importance of flooding in determining the site of the nesting colony is noted; adverse conditions caused by a rise in the water-level of Lake Mweru Wantipa appear to have completely destroyed the nests. The instability of such environments does not offer much chance of regular and permanent breeding, and may influence local movements on the part of the birds.     

ASPECTS OF THE BEHAVIOUR AND ECOLOGY OF MIXED-SPECIES BIRD FLOCKS IN KASHMIR

Mixed-species flocks of birds were observed between the end of July and late August, principally at Daksum, Kashmir, 2250 m. The species composition and the numbers of individuals in flocks changed during this period; these changes are attributed to resident territory holders and migrant birds joining the flocks. Within the flock different species showed some differences in foraging stations, but nevertheless often appeared to be taking the same type of food. Participant species had different roles in the flock organization. Behaviours involving the entire mixed-flock acting as a unit included path reversal after encounters with avian predators and a tendency to follow set routes. The mixed- species flock exerted an attractive influence on aggregations of species not normally participant.
Similarities between the flocks described in this study and those recorded by other workers are discussed. While different species may derive different benefits from joining these flocks, advantages that could benefit some or all participants include the receipt of information on good feeding areas in an unfamiliar locality, the avoidance of time wasted on feeding on substrates which have been very recently harvested, the beating effect to increase prey availability, and enhanced safety from predators, perhaps through differential alertness of different species and specialized anti-predator behaviour.     

5. FIELD OBSERVATIONS,NORTHERN PROVINCE,NORTHERN RHODESIA

Cooper, J. 1986. Biology of the Bank Cormorant, Part 4: Nest construction and characteristics. Ostrich 57: 170–179.

Bank Cormorants Phalacrocorax neglectus construct their nests of material gathered by diving. Males undertake diving bouts of approximately 3–5 min, made up of several dives lasting on average 28 s. Nest material is gathered throughout the breeding cycle: number of diving bouts per day varies from a mean of 7,6 during pre-egg laying to 1,5 bouts per day when rearing young in the nest. Nest building recommences within 24 h of loss of nest due to storms. Both sexes occasionally steal nest material from the nests of neighbours. Bank Cormorants sometimes defecate onto their nests. This is assumed to make the nests better able to withstand rough seas. Nest construction takes approximately 34 d, a period similar to that of other ground-nesting species of cormorants. Construction of a nest in 34 d represents 238 diving bouts of a total duration of 18 h. Nests are heavy (up to 6 kg) and are made up primarily of seaweed. Feathers, sticks and artificial material are also incorporated into the nest. Bank Cormorant nests are large (up to 54 litres in total volume). Nests do not change significantly in size between egg laying and hatching. Nests in which at least one egg hatches are larger in all dimensions measured than those in which no eggs hatch. Nests are larger at the time of laying of repeat clutches than at the time of laying the first clutch. The Bank Cormorant's seaweed nest has enabled it to breed on bare offshore rocks where no nest material exists. The species' large nest is a necessary prerequisite for successful breeding close to the sea.     

SOME NOTES ON THE BIRDS OF THE ISOKA DISTRICT OF THE NORTHERN PROVINCE OF NORTHERN RHODESIA

Dean, W. R. J. 1978. Moult seasons of some Anatidae in the western Transvaal. Ostrich 49:76-84.

Spurwinged Geese Plectropterus gambensis, Egyptian Geese Alopochen aegyptiacus, Yellow-billed Ducks Anas undulata, Redbilled Teal A. erythrorhyncha and Southern Pochard Netta erythrophthalma have a flightless moult mainly during the dry season, from April to August, in the western Transvaal. South African Shelduck Tadorna cana moult during October to February after breeding during July and August. The Cape Shoveller Anas smithii has two main flightless periods, April-May and October-January. Cape Teal A. capensis have been recorded in flightless moult in October, December and January.

The duration of the flightless period correlates with wing length; larger and longer winged Anatidae require proportionally more time for wing moult than do smaller and shorter winged Anatidae.

Geese and shelducks moult on large open lakes with an open shore. Ducks have been recorded flightless on lakes and dams, with or without emergent vegetation.     

MODELLING THE DISTRIBUTION OF BIRD SPECIES IN SWAZILAND IN RELATION TO ENVIRONMENTAL VARIABLES

Parker, V. 1996. Modelling the distribution of bird species in Swaziland in relation to environmental variables. Ostrich 67: 105–110.

Logistic regression was used to model the observed distributions of 335 species in Swaziland in relation to variables representing the geology, topography, climate and vegetation types of the study area. Reporting rates were used to represent the relative densities of the species. For each species, the variables which were significantly associated with the distributions were identified. The combination of geological, topographic and climatic variables was found to account more fully for the variation in relative densities than the vegetation types. The models accurately predicted the observed distributions of most bird species.     

6. MIGRATION NOTES,CHINSALI, NORTHERN RHODESIA

Jarvis, M. J. F. &; Currie, M. H. 1979. Breeding of captive Knysna and Purplecrested Louries. Ostrich 50:38-44.

Knysna Louries Tauraco corythaix and Purplecrested Louries T. porphyreolophus were studied in captivity to determine food requirements and feeding habits, clutch size, egg measurements, incubation periods, as well as the nestling period, anatomical and behavioural development of chicks, and aspects of parental behaviour.     

哈萨克斯坦北部轮藻植物的分布与生态学研究

哈萨克斯坦北部已发现26种轮藻植物,其中以Kockchetav丘陵地区最为丰富。轮藻植物生长的盐度范围为0．2—44．9g／L,一般生长于盐度不超过1—5(8)g／L的淡水或微咸水环境。在盐度高达41．1—44．9g／L的水体中,仅发现Lamprothamnium papulosum。轮藻植物生长的最大水深为7m,多数种生长的水深不超过1m。轮藻生长的主要底质类型为砂及粉砂质。一些种类如Chara kirghisorum,C．glopbularis,C．tomentosa和Nitellopsis obtusa构成稳定的植被,而其它种类构成湖区周期性干涸环境中短时间生长的水生大型植物群落的一部分。     

试论晚白垩世以来气候、地理等因素的变化对鼍类的进化及地理分布等影响

现存的鼍属只有两个种:即东亚的扬子鳄及北美的密河鳄。虽然这两个种的性质、纬度分布以及生态环境等都十分相似;但两者的水平分布的距离却几有地球的半圈。本文根据有关鼍类的进化、迁徙等的历史资料,对此进行了初步的探讨。