No description available.

The growth, survival, and causes of mortality of Eider (Somateria m. mollissima) ducklings were studied on the Ythan estuary, Aberdeenshire, Scotland from 1972 through 1974. Rates of growth of tagged ducklings in the field were variable, and were slower than in captives. Causes of slow growth may have included parasitic infections and food, but cold alone was ruled out in experiments as a cause of retarded growth. Estimation of age in the field from appearance or size of ducklings was unre-liable, although commonly used in other studies. Fiedging success was less than 10%, with most of the mortality in the first two weeks of life. The principal cause of mortality was predation by large gulls (Larus argentatus and L. marinus), which took 80% of all ducklings. Predation was approximately 4 times higher in bad weather than in good. A secondary cause of mortality was parasitic disease; almost all ducklings examined were infected by renal coccidiosis (Eimeria somateriae), but only 8% were estimated to have suffered potentially lethal damage. Food was not considered to be a factor causing mortality; however, it may interact with other factors in bad weather, when some ducklings may fail to obtain a sufficient quantity, and when increased dis-persion while foraging raises the risk of predation. Bad weather did not kill ducklings directly, but was highly correlated with mortality over most years; it is probably the ultimate factor determining survival in most years, acting through others, chiefly predation. Alternate prey for gulls may be responsible for occasional years of very high survival. Broods commonly formed creches of up to 20, but larger creches were a function of duckling density. Creches up to 20 were advan-tageous in reducing risk of predation, but there was no advantage above this size. It was concluded that formation of small creches has been selected for, but large ones are a secondary trait per-mitted by gregarious tendencies and contingent on density.

The annual energy budget of a weasel population in farmland near Newburgh, Aberdeenshire, was studied for two years. Data on population dynamics were collected by live-trapping weasels, and data on metabolism were obtained from laboratory experiments. Fifty four male and 24 female weasels were trapped 623 times, and the sex ratio of both individuals and captures was significantly different from 1:1. Females had a lower trappability than males, which probably concealed an equal sex ratio in the population. The numbers of females on the study area were calculated from male numbers on the basis of an equal sex ratio. Most weasels (23) were present in late summer, and the average density was one weasel/7.7 ha. Most males were residents and were caught regularly, but the residential status of females was difficult to determine. Weights of trapped weasels varied widely, but tended to decline between summer and mid-winter. Few breeding data were collected. Analysis of scats from trapped weasels showed that small rodents, especially short-tailed voles, were the most frequent prey. As temperature decreased the average daily metabolic rate (ADMR) of both sexes increased, with a relatively greater rise for females; ADMR was also influenced by body weight and activity. Elongate mustelids have higher metabolic rates than normally-shaped mammals of similar weight. Regressions of ADMR on temperature were significantly different for males and females, that for females having the steeper slope. Females ate relatively more each day than males : mean daily consumption was 0.33 g/g/day for males and 0.36 g/g/day for females. Daily faecal production and the energy lost in faeces and urine were influenced by the proportion of indigestible material consumed; on low-bulk diets weasels lost as much energy in urine as in faeces. Assimilation efficiency was reduced by up to 10% on bulky diets; the range for four foods was 73-83% for males, and 76-83% for females. In 1972-73 minimum estimates of the standing crop, energy flow, and annual energy budget were lower than in 1971-72. Energy flow was greatest in summer, and least at the end of winter, and averaged 3865 kcal/ha/yr; mean annual consumption was 4930 kcal/ha/yr. The seasonal consumption of six major food types was calculated, and minimum estimates were obtained of the numbers of small rodents eaten. Factors favouring selection of sexual dimorphism were discussed, and a new hypothesis, that sexual dimorphism is advantageous for breeding females, was presented. Calculations for weasels showed that small females when breeding required daily 20% less energy than did hypothetical 'male-sized' females. Data on movements and dispersion were presented in Appendix 2. During the breeding season the winter territorial system of males broke down, and their movements were greatest. The seasonal dispersion of males was described, but there were few data for females. The average size of male territories was 13.3 ha.

No description available.

This study researches the potential for using hyperspectral remote sensing to identify the phytoplanktonic composition of a freshwater bloom. Six novel analytical techniques were developed to identify phytoplankton class from reflectance spectra. These techniques offer the water manager a variety of means to identify the dominant phytoplankton class in a target water body. Identification of phytoplankton class is possible because certain photosynthetic pigments contained within phytoplankton cells are taxonomically significant, being indicative of a particular class. The detection of these pigments can be used to identify the presence of a particular phytoplanktonic class in an aquatic system. It is possible to identify these pigments using optical methods because they exhibit unique spectral absorption signatures. Such pigment absorption features are manifest in the composite reflectance signature from water bodies as measured by remote sensing instruments. However, due to the presence of the spectral features from other photosynthetic pigments and the other optically active components of water bodies, extracting from reflectance spectra the spectral information pertaining to individual class marker pigments can be difficult. The phytoplankton class identification techniques presented in this study were developed using absorption and reflectance spectra from pure cultures of phytoplankton. The reflectance spectra were measured in the controlled environment of a laboratory based experimental tank designed for this study. The class identification techniques were tested on field and airborne reflectance spectra measured from a eutrophic inland lake.

No description available.

No description available.

Long term data on the population of Eiders (Somateria mollissima ) breeding at the Sands of Forvie, Scotland, have been analysed to investigate changes in numbers and regulation of the population. The importance of immigration and emigration and the ability of the population to maintain itself from its low reproductive output were also investigated. Most of the adult population migrates to the Tay and Forth estuaries in winter, but several hundred birds remain on the Ythan estuary throughout the winter. First year birds usually disperse to coastal areas within 50 km of Forvie. The movement patterns of the population are described in detail. The size of the summer and winter populations increased slowly over the last 20 years. The average annual rate of increase of the winter population was 4%. Tests for density dependence indicated that both summer and winter populations were regulated. The size of the winter population declined between October and March in a density dependent manner. It is suggested that this is related to a decline in the abundance of the Eider's principal prey species, Mytilus edulis, over the same period. Some female Eiders bred when they were two years old, and most did so by the time they were four. Young females laid later, had smaller clutches and were lighter in weight at the start of incubation than older birds, but egg size did not vary with age. The number of ducklings fledged was very low in 16 out of the 21 years studied. Thus although losses due to breeding failure were the largest mortality factor in the annual cycle, changes in the summer population were not related to variations in duckling production. Egg production and breeding success were not density dependent. Losses of adults between summers were density dependent, and were largely responsible for changes in population size. In important component of these changes was the apparent failure of part of the population to attend the colony in some years. First year mortality was density dependent. Average survival rates were estimated to be 67% for first year birds and 96% for adults. About half the males reared at Forvie emigrated, and some joined the Baltic breeding population. Most Forvie bred females returned to the colony to breed. On average the population was able to maintain itself from its own reproductive output, but limited immigration did take place in some years.

The feeding activity of wild and captive red grouse is similar. In the evenings, both have marked peaks of feeding which are greater in winter than in summer, and monthly variations in their food intake are also alike. Heather forms at least 90% of the diet of wild red grouse for most of the year. At one moor it was calculated that each bird would eat between 18 kg and 25 kg (by dry weight) of heather in a year, which means that grouse eat only 1.3 - 2.4% of the total annual production of heather shoots and flowers there. The food intake of captive grouse was positively related to body weight and day-length, and negatively to air temperatures. It increased during the summer moult, and hens ate most while producing eggs. The preferences of grouse for particular ages of heather were studied on three moors and also in captivity. Preferences in the wild were associated with the interrelated factors of density, age, height an chemical composition of heather. The last three factors affected preferences separately in captivity, where preferences also varied with the physiological state of the birds. Heather preferences of free ranging mountain hares, sheep and red deer were also studied. Wild grouse selected heather with a relatively high concentration of nitrogen and phosphorus compared with the available heather; this, confirmed, earlier work. The: amount of selection was related to feeding rates and sometimes to the mean weight of heather particles eaten. In autumn and winter, grouse selected less in the evening, but did not change their selection with time of day in spring. In spring, both sexes were equally selective for nitrogen and phosphorus, but the hens' food was richer in calcium than that of cocks. However, hens ate much more food in spring than cocks. Wild grouse chicks ate a more varied diet than adults, but still mostly heather shoot tips. They often ate invertebrates during their first few weeks, but these formed only a small proportion of the diet by dry weight; chick survival was not related to the abundance of invertebrates available. Chicks selected heather containing more nitrogen, phosphorus and calcium than adults did.

Some ecological and economic aspects of the grasscutter Thryc x8.yr.ia Teasainck as a protein source in Ghana were investigated from July 1970 to June i 973o The grasscutter's diet consisted of 27 grasses and 14 herbs or shrubs* Crops were frequently eaten. Its diet, seasonally related to rainfall, also met its water requirements. Females produce two litters a year: breeding throughout the year with peaks related to rainfall. The litter size is 1 tc 8 with a mode of 4 and a sex ratio of unity. Litter size and total litter weight are correlated with maternal weight. The gestation period was 155 - 9 days, with a specific foetal growth velocity of 0.04, A post parturn oestrus may occur. Birth weights vary within litter mates and embryos implanted at the cervical end(s) of the uterine horn(s) are usually heaviest, A incidence of embryonic resorption occurred. In captivity, cubs were usually weaned onto adult diet when 4 weeks old and attain sexual maturity at five months. Females had their first litter at a year when they weighed 1 kg. Tooth eruption pattern and eye lens weight together with the appearance of mammae in females and perineal stain in males were useful criteria of age. 39*732 grasscutter carcasses, weighing 181,327 kg. were sold for '?38,517o35o Carcass weights, up to 8.9 kg. in males and 6.9 kg. in females were recorded. About 13% of the .7eight is edible meat. it is the third (to mutton and bushmeat) most expensive meat on the market. It is complementary to beef but substitutive to mutton. It has great demand and its price continues to rise rapidly. The grasscutter is a potential pest whose control must be kept under vigilance, but whose domestication was found to be technically and economically feasible.