No description available.

No description available.

No description available.

In 1984-5 the carabids and staphylinids on ten isolated limestone outcrops and intervening blanket peat within the Moor House Reserve, Cumbria, were investigated. In 1986 a subsidiary study on similar habitats was made at Tailbridge Hill, Cumbria. Pitfall and window traps sampled beetles from the ground and air respectively. Numbers and alpha diversities of carabids and staphylinids were higher on the Moor House limestone outcrops than on the blanket peat. The outcrops acted as isolates to many species, but also suffered considerable contamination by adjacent peat faunas. Limestone species taken on outcrops exhibited a positive species: area relationship consistent with island biogeographical theory. Peat species taken on outcrops showed a negative species: area relationship. Overall, species of staphylinid were positively, and carabid, negatively, correlated with outcrop size. Dispersal of species between habitats was influenced by body size, degree of hygrophily and flight activity. Flight by carabids was negligible, but most staphylinids could fly. Weather conditions were probably the primary cause of this difference between taxa. Flight by staphylinids was related to the stability of the habitat or resources involved. All Nomadic species could fly whereas flight by Peat species was negligible. Limestone species showed relatively high levels of flight activity attributable to the need of many rarer species for regular dispersal between outcrops to spread the risk of extinction. The aerial fauna at Moor House had three components, with species deriving from the immediate habitat, moorland habitats nearby, or regions beyond the Reserve. A considerable influx of staphylinids (and aphids) onto the Reserve occurred in July-October as aerial plankton was carried in from the west by prevailing winds. The applicability of island biogeography theory to the Moor House system, and to 'habitat islands' in general, is discussed.

Blue-eyed shag chicks have been ringed in almost every year since 1969 at two colonies on Signy Island. In this study, over 40% of breeders (801 pairs in 1987) were ringed and of known age, and during the breeding season adults were readily recaptured. Annual adult survival rates during the study averaged 0.86, although the mean annual survival rate between the early 1980's and 1987 was lower, averaging 0.76. There was no difference in the annual survival rate in relation to sex or breeding experience, but birds older than 11 years showed evidence of decreased survival rates, of about 0.04 annually. The first year survival rate averaged 0.36 but varied widely between 0.03 (in 1979) and 0.69 (in 1984). Low first year survival rates occurred about every four years. Only mean monthly temperature in April and the duration of sea ice were selected as explaining variation in first year survival rates and together they accounted for over two-thirds of the variation. Post-fledging survival rates were independent of hatching order, although only a few last-hatched chicks survived the nestling period. Although movements to and from neighbouring colonies could not be monitored thoroughly, no ringed birds were seen during searches of the two nearest colonies, and the rate of colony exchange between the two Signy colonies suggested that established breeders exhibited a high degree of faithfulness to their colony, only 0.1% moving each year. Recruits tended to return to their natal colony, and only 2.4% moved away between the two Signy colonies. Blue-eyed shags showed deferred breeding and whilst a few individuals began breeding at two years, most waited until their third and fourth year and some delayed breeding until six years old. The modal age of first breeding varied between years being earliest in 1987 (3 years) when recruitment was also high. Over the age range at which most birds recruited, there was no difference between the sexes in the age of first breeding. Prior to the year in which they first bred, young shags visited the colony to which they subsequently recruited and the number of visits per bird increased with age. Older pre-breeding birds also made visits earlier in the season. Low mate fidelity was normal, only 39% retained the same mate in the following breeding season. Of those which changed mate, divorce accounted for 46%, and the annual rate of divorce declined in relation to increasing age and breeding experience. A comparison of the divorce rates of similar aged birds with different breeding experience showed that recruits were more likely to divorce, suggesting that breeding experience was more important in divorce than age alone. Pairs which divorced in the current year had had lower mean clutches, broods and fledged fewer chicks in the previous year compared with those which kept the same mate. However, pair stability during the previous year had no effect on the breeding performance in the current year. Divorce was associated with further divorce in the following year. Both sexes showed a high tendency to re-nest within 12 m of the previous year's nest, although this was less marked in females. Re-use of the previous year's nest was low. A high proportion of pairs had partners of similar age, 46% being of equal age and 70% differing by a maximum of one year. Nearly twice as many equal aged pairs arose compared with the number expected if mating was random with respect to age, and the proportion of equal aged pairs declined among older birds. With respect to breeding experience and pair stability, experienced pairs and those which changed mates did not form more equal aged partnerships than expected by chance, and only for recruits did more equal aged pairs form than expected. Breeding experience was weakly related to breeding performance and the effect was stronger in 1987 than in 1986. Younger males built poorer quality nests than older birds, but it was not possible to resolve the effects of age and nest quality independently on breeding success.

The thesis describes a study on the ecophysiology of the moss Hydrogonium fontanum (C. Mail.) Jaeg., the dominant plant at a waterfall in Saudi Arabia. The influence of environmental variables and water stress on the growth, stress metabolite accumulation and phosphatase activities of the moss was studied in laboratory axenic culture along with observations and experiments conducted in the field. The variables chosen for growth experiments were light flux, flooding, nutrient concentrations and water stress. For phosphatase activities, the influence of temperature, pH, ions, water stress were studied. Differences were found in phosphatase activities for rhlzoids, protonema and leafy shoots of the moss and, therefore, the phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities of these fractions were also investigated. H. fontanum was originally collected from the tufa-depositing waterfall (Water chemistry - 44 mg 1(^-1) Na, 44 mg 1(^-1) Ca). High Na and Ca had significant positive effect on yield of the protonema under the laboratory conditions. Low light intensity (10 µmol photon m(^-2) s(^-1)) decreased the yield, but high light intensity (90 µmol photon m(^-2) s(^-1)) increased the yield of the protonema. The moss showed no response to water stress in respect to praline accumulation. Protein content decreased significantly over 48 h with increase in water stress. The Influence of water stress was greater in terms of dry weight and chlorophyll content changes in protonema than in leafy shoots. The protonema was capable of using various organic P substrates as sources of phosphorus and showed both PMEase and PDEase activities. PMEase and PDEase activities were detectable in all moss fractions (rhizoids, protonema, leafy shoots). Laboratory grown material showed higher activities than field grown material. Rhizoids produced the highest PMEase and PDEase activities among the moss fractions. Some leafy shoots collected from the field had low phosphorus content with high phosphatase activities, while others had high phosphorus content with low phosphatase activities. Changes in phosphatase activities in batch culture were studied in relation to growth rate. PMEase activity was first evident when cellular P was 1.15% with low activity (0.117 µmol pNP mg d. wt(^-1) h(^-1)) and PDEase appeared 4 days later when cellular P was 0.54%. The activities increased up to day 12 after which the activities maintained this level. The optimum temperatures, measured over a period of 1 h, for PMEase and PDEase activities were 60 ºC and 65 ºC with pH optima of 5.5-6.0 and 6.4-6.8, respectively. Of the six ions tested, Ca, Zn and P had significant inhibitory effects on the activities at the highest concentration used (10 mM).Drying the moss decreases PMEase and PDEase activities by about 23% and 21% (5-d) and 3.7 and 2,8 times (3 months), respectively. Water stress (PEG treatment) also reduced significantly the activities of PMEase and PDEase with a greater effect on the activity of the latter. A brief comparison in PMEase activity using two different substrates p- nitrophenyl phosphate (pNPP) and 4-methylumbelliferyl phosphate (4-MUP) was made to investigate the pH optima and time course. PMEase activity measured using 250 µM 4-MUP was about 60% of that measured using the same concentration of pNPP.

Both plovers were studied at Lindisfame, Northumberland, during three non-breeding seasons; and the Ringed Plover while breeding at Lindisfarne and in NE Greenland. In winter both species fed principally on intertidal polychaetes, but prey differed in different sites. Food requirements in winter could not be met during daylight. Prey capture rate at night was lower than by day. Plovers carry large fat reserves in winter probably to buffer the effects of cold, windy weather, which reduces their feeding rates more than those of sandpipers. Plovers search for prey apparently by visual means (without the tactile element used by other waders). At the sand surface intertidal invertebrates increased their activity (which enabled plovers to detect them) with increasing temperature; also in some cases with foot- vibration by Ringed Plovers. With an increase in prey availability, the birds increased their capture rate first and then their selectivity of prey sizes and species. A simple model is developed to describe the foraging behaviour and its modifications in relation to prey availability and distribution. The presence of other shorebirds also affected prey capture rate. Nocturnal foraging is discussed in relation to visual foraging and invertebrate activity. An attempt is made to predict the minimum densities of prey required for energy balance in various conditions and to compare visual and tactile foraging strategies of plovers and sandpipers. Growth rates of Ringed Plover chicks were similar in all areas and diurnal rhythm in activity more marked in the Arctic. The development of foraging from hatching to first winter is described in comparison to that of adults and survival rates for various age-groups assessed. Food supply does not appear to limit growth or chick survival but feeding ability may become important in autumn.

The habitat requirements and population dynamics of Redshank, Dunlin and Ringed Plover on internationally important breeding grounds in the Western Isles of Scotland were studied from 1985 to 1987 using individually colour-ringed birds. Twenty-six habitat types were recognised at four study-sites on South Uist. The temporal and spatial use of the habitats by the three species were quantified. Redshank used a wide variety of pasture, marsh and water's-edge habitats and occurred mainly on "blackland" areas. Dunlin were largely confined to areas of old fallow machair and machair marsh. Ringed Plover occurred almost exclusively on the areas of machair used for cultivation. Redshank did not defend breeding territories and individuals ranged over wide areas. Dunlin and Ringed Plover held breeding territories within which most of their activities were confined. Late in the breeding season the seashore was an important feeding habitat for Dunlin and Ringed Plover. Breeding densities varied markedly between major habitat divisions and appeared to be mainly determined by the availability and quality of potential nest-sites as indicated by their conspicuousness to avian predators. Adults, especially males, nearly always returned to their previous year's nest-site or to close by. Young males bred significantly closer to their natal site than young females. Most birds settled within 4 km of their natal site. Breeding success, first-year and adult survival, and the age of first’ breeding were evaluated. The data were used to predict population trends, which were compared to results from large-scale population surveys. It is concluded that Redshank and Dunlin numbers are approximately stable but that Ringed Plover are decreasing. Avian predation was the main factor limiting productivity. Both early season and well concealed/camouflaged nests were more likely to be successful.The conservation of these birds is discussed and some measures suggested that might increase their productivity.

A Study was made of the ecology of aquatic bryophytes and their accumulation of metals in rivers of northern England. Field surveys and experiments in the field and laboratory examined the effectiveness of bryophytes as monitors of heavy metal pollution. A survey of 105 river sites (10-m reaches) with Rhynchostegium riparioides was carried out, together with a seasonal survey of this species at seven sites, which also included data for two other species. Details of the aquatic bryophytes present, water chemistry and metal concentrations in mosses are given. The ecological ubiquity of Rhynchostegium was described using principal components analysis and discussed in relation to other macrophytes. A biometric study revealed that marked interpopulation differences in gametophytic characters were correlated with water chemistry variables (NH(_4)-N, PO(_4)-P, Cl, Na) indicative of organic pollution. Significant linear regressions were found between accumulation and aqueous concentrations of Zn, Cd, Ba and Pb. A multiple regression of these and other chonical data suggested several factors had significant effects on accumulation. Seasonal effects were largely chemical in nature, rather than a function of the plants themselves. Experiments supported several findings from the surveys. Zinc uptake proceeded more rapidly than loss and was influenced by aqueous Mg, Ca and humic acids, but not PO(_4)-P, NO(_3)-N or Si. Accumulation was greater in tips of Rhynchostegium than Amblystegium riparium or Fontinalis antipyretica. Results indicate that bryophytes are useful as monitors of pollution. Rhynchostegium in particular is recommended for its ecological ubiquity, its presence in a wide range of aqueous metals and greater accumulation. Applications of bryophytes for specific uses are outlined, with recommendations for different situations. A new model, based on slopes of accumulation, is proposed as a predictive tool.

The effect of re-seeding of heathland on the breeding ecology of whimbrel in Shetland was studied from 1986-1988, on five study sites located on the islands of Unst and Fetlar. A total of 36-45 pairs bred on these study sites in each year, and a large proportion of the breeding adults were individually colour ringed. Heathland was the main nesting habitat for whimbrel. Established pastures and areas ploughed or harrowed before re-seeding were avoided as nesting habitats, but some pairs nested on areas subjected only to surface re-seeding. Avoidance of ploughed or harrowed re-seeds was associated with changes in vegetation composition and structure, and such re-seeds lacked attributes important in the selection of nest-sites by whimbrel. Habitat change was less marked in surface re-seeds. Ploughed or harrowed re-seeds were used extensively as feeding habitat by adults during the pre-laying period, and evidence was obtained to indicate that re-seeding improved feeding conditions for adults. Measures of breeding success were positively correlated with egg volume, and negatively correlated with laying date. However, the improved feeding conditions on re-seeds for females prior to laying were unlikely to have provided major benefits for breeding success via effects on either egg volume or laying date. Approximately 30% of all broods studied used re-seeds at some stage prior to fledging. Although some broods did show preferences for this habitat, there was little evidence that this was associated with either, decreasing the risk of predation on chicks, or improving chick food supply. The survival of chicks to fledging did not vary according to the habitat-use of broods. Both nesting densities and productivity varied between study sites. The possibility that areas of heathland differ in their suitability as breeding habitat for whimbrel is considered, and the implications of this in assessing the effects of re-seeding heathland are discussed. Over the study period the overall production of fledglings from study sites was probably in excess of that required to balance adult mortality. This result is consistent with the current increase of the whimbrel population in Shetland.