No description available.

Four species of owls were studied in a 'farmland area surrounding the lower Ythan Valleyr Aberdeenshire from 1972 to 1975. Twenty-six pairs of Tawny Owls were located in isolated woods and large areas of woodland where territories were small. Radiotransmitters were fitted to owls in isolated woodlots to determine their nocturnal hunting ranges. Birds hunted extensively over open farmland and plantations away from their core-areas of woodland or farm steading. A strong selection was displayed for mixed deciduous woodland which formed less than 5% of the study area. Exclusive territories were maintained up to 3 km in length. Fewer Long-eared and Short-eared Owls were found in the study area and less information was obtained on their hunting ranges. Barn Owls were located infrequently. Diets were determined by the analysis of pellets and the identification of food items at nest sites. The vole, Microtus, was the most important species taken by all owl species except the Barn 0171 for which shrews formed the greatest biomass. Changes in the diet of Tawny and Long-eared Owls were found in the breeding season when more rabbits and Starlings were taken. Trapping in eight habitat types revealed that small mammals are most abundant in autumn and least abundant in spring and early summer. Size of hunting ranges, use of habitats and diets of owls were related to changes in the availability of their prey. Interspecific competition between owls in the study area is considered to be avoided by temporal activity and habitat selection.

From a review of the literature on supra-littoral rockpools from the beginning of the century, it is shown that there in a paucity of knowledge on the community structure of these pools and the factors responsible for it. The methods used in the study are described and discussed. The physical and chemical changes in the water of nine supra-littoral roekpools at Greg Hess near Aberdeen are described and a classification of these pools based on salinity is put forward. The fluctuations in the nitrogen content of the bottom deposit of each pool are described and the main factors affecting it are discussed. It is concluded that it is derived principally from the micro-organisms which break down the dead fauna and flora to provide a rich supply of food for the living fauna. It is shown that the reproductive cycle of Enteromorpha intestinalis is accompanied by changes in the quantity of carbohydrate in the thalli. Large reserves are present prior to sexual reproduction, while smaller reserves are built up before sexual reproduction occurs. The quantitative distribution of E. intestinalis is not seriously affected by salinity in this region. It seems likely that E. intestinalis is the principal primary source of organic matter in the pools. The distribution of the fauna over the nine pools depends on the salinity tolerance range of the individual species and two main zones can be distinguished with a transitional zone of overlap between them. The harpacticoid, Tigriopus brevicornis dominates those pools with an overall salinity range 0.5%o - 45%o and Nitocra spinipes dominates those pools where the salinity does not rise above 35%o. The course of the life history of the principal members of the fauna is described and the causes of the fluctuations in the population density of each species in each pool are discussed. The community of each pool is made up of those species which can not only tolerate but can reproduce under the environmental conditions prevailing in each pool. The dominant organisms are the harpacticoid copepods but the balance can be upset by prolonged changed in the environmental conditions. Experiments to determine the relative importance of temperature and salinity on the survival of the harpacticoid copepods and the ostracod Loxoconcha baltica are described. Survival of T. brevicornis in hypersaline water improves as the temperature rises while lower temperatures favour survival of If. 3pinipes in hyposaline water. Mesochra lilljeborgi has a very narrow range of salinity and temperature tolerance. The females of all three species display a higher survival range than the males. Salinities below 35%o are optimal for L. baltica. Micro-organisms present in the bottom deposit form the principal food of T. brevicornis although E. intestinalis and other copepods, including its own species, can be utilised. Salinity affects the rate of food intake. It is concluded that salinity is the dominant factor affecting the organisms of the rockpool communities and their maintenance. Food supply is rarely a limiting factor. A scheme is presented of the zonation-and classification of supra-littoral rockpools based on salinity and faunal composition. The practical application of this scheme for other localities is discussed.

No description available.

The physiological ecology of bats and turtles was investigated. A Doppler-radar unit was developed to non-invasively record the ventilation rate of unhindered free-hanging microchiropteran bats. The technique was then used to examine the arrhythmic breathing pattern of torpid pipistrelle bats (Pipistrellus pipistrellus). At ambient temperatures ranging from -1 to 14 oC arrhythmic breathing was most marked at colder temperatures. Active breathing could only supply a small proportion of the total O2 uptake, suggesting that during apnea the glottis remained open allowing a significant diffusive influx of O2. Radars were used to monitor the winter activity of a captive colony of brown long-eared bats ( Plecotus auritus). During winter these bats were found to emerge from their hibernaculum with a high daily probability (0.4 to 0.9), and upon emergence they tended to feed first and then drink. A model was developed to predict the optimum clutch size of loggerhead sea turtles (Caretta caretta). Due to their high energy expenditure whilst on land, it was predicted that turtles should lay clutches that are as large as possible. Hence clutch size should be constrained by the egg carrying capacity of the individual, and so it was predicted that larger individuals should lay larger clutches. This was found in a population of loggerheads in Greece. Clutch volume was found to be independent of the inter-nesting interval between successive nests laid by the same individual, and was found to decrease as the nesting season progressed due to a reduction in egg size with successive clutches. Nest site selection by nesting loggerhead turtles was studied. Sand temperature was found to play no part in nest site selection. However, nests were not deposited at random, but tended to be laid away from the sea close to vegetation that backed the beach. This pattern of nest placement was found to maximise hatchling survival. The emergence pattern of hatchling loggerhead turtles was monitored using a portable radar. Most hatchlings emerged at night, and hatchlings came out of all nests on more than one night (maximum 11 nights). Evidence suggested that the rate of cooling of the deep sand (≥ 15cm) was a factor initiating emergence. When the sand cooled faster in the evening, the hatchlings emerged earlier. The remigration pattern of adult sea turtles to a nesting beach over several years showed that individuals varied in their tendency to return in subsequent years. Evidence supported the hypothesis that the lower tendency of turtles seen nesting less than twice to return in subsequent years was due to them nesting on other beaches. A single female turtle was tracked by satellite for 58 days during the nesting season. The transmitter was attached after the turtle had been observed nesting. The satellite data revealed that the turtle subsequently made only localised movements and nested 3 more times, although never returning to the original nesting beach. Finally a method was developed to rigorously quantify the probability of identifying a nesting event by a turtle by satellite tracking, using field data combined with prediction software to calculate the time of satellite overpasses.

The spacing behaviour and breeding of shelduck on the River Ythan Estuary, Scotland, was studied during 1970 -1972. Sixty percent of the study population were individually colour-ringed; the marked sample did not introduce bias. Birds returning to the study area during December - March associated in flocks, individuals joining that flock nearest their previous year's territory. During the breeding season, the population comprised territorial pairs and a non-breeding flock (one and two-year olds and unmated adult males). Pairs returned to the same territory each year. Territorial behaviour was studied in detail and showed that the precise location of the territory shifted constantly throughout the breeding season. Average territory size was 4.0 ha. A single statistic was devised in describe both the size and the pattern of utilization of parts of the territory. All territorial pairs attempted breeding but only 37.5% appeared with ducklings. The main cause of nesting failure was thought to be disturbance at the nest burrows by other, mainly non-breeding shelduck. Ducklings were reared in confined nursery areas, fledging in approximately eight weeks. Within each nursery area, ducklings frequently transferred from one brood to another; this creching was the result of a high density of broods. Creched ducklings suffered a higher mortality rate than those reared in family units. Most ducklings died during their first week of life (causes mainly unknown) and 9 - 37% ultimately fledged. This production was insufficient to replace adult losses0 There was no evidence that the size of the Ythan population was internally regulated and immigration was considered the major factor maintaining the population at its present size (153 - 179). Factors controlling the extent of this immigration remain unknown.

No description available.

No description available.

No description available.

Controlled laboratory studies showed that the toxicity induced by biologically relevant trace metal species of Cu, Cd, Pb and Zn on embryo-larval development occurred at concentrations in excess of those found in the natural environinent, except for Cu in metal perturbed areas. Average free ion concentrations inducing 50% abnormal development( EC50feew) ere determineda s 0.23 nM CU2+8, 8.0 rim Cd2+,1 28 nM Zn2+a nd 3 62 nM Pb 2+ . However, the response to some binary metal combinations indicated enhanced (synergy) toxicity at concentrations relevant for estuarine waters (e. g. EC5of'. for Cu2+i n the presence of C(ý: +, Zn2+a nd Pb2 +w as 0.004,0.02 and 0.04 nM, respectively). A comparison of voltammetric instrumentation (voltammetric in situ profiling (VIP) system versus Hanging Mercury Drop Electrode with potentiostat) highlighted the advantage of high resolution measurements (ca. 20-60 min intervals) for environmental studies and the minimisation of artefacts associated with discrete sampling methodologies. Field-based studies were carried out in two contrasting estuaries in SW England, one heavily impacted with metal contaminants (Fal Estuary) and another subject to greater variety of anthropogenic influences (Tamar Estuary). High resolution in situ trace metal speciationm easurementsc, arried out over tidal cycles, identified important information on the temporal and spatial distributions of biologically relevant dynamic (<4 nm) metal species of Cd, Pb and Cu. Variation in embryo-larval responses to discrete samples from these estuaries, effectively paralleled the metal speciation measurements showing enhanced toxicity when the marine water influence was at its lowest. In both systems, the results indicated that the combined effect of the metals studied was likely to have provided a significant contribution to the bioassay response. However, the difficulty in de-coupling the speciation measurements with biological responses was evident and supports the need for more comprehensive campaigns to study the impact of contaminants on ecosystem functioning. Bioassay and metal speciation analysis techniques were complementary, exhibiting high sensitivity and rapid responses, and would be considered effective screening tools for waters subject to intermittent inputs of metal contaminants and areas with recognised pressures. The integrated approach has extended our knowledge of trace metal speciation in estuarine environments and their effects on the developing embryos of the Pacific oyster. This approach has the potential for wider application.