Foraging ecology, fluctuating food availability and energetics of wintering brent geese

Changing energy requirements and dramatic shifts in food availability are major factors driving behaviour and distribution of herbivores. We investigate this in wintering East Canadian High Arctic light-bellied brent geese Branta bernicla hrota in Northern Ireland. They followed a sequential pattern of habitat use, feeding on intertidal Zostera spp. in autumn and early winter before moving to predominantly saltmarsh and farmland in late winter and early spring. Night-time feeding occurred throughout and made a considerable contribution to the birds' daily energy budget, at times accounting for > 50% of energy intake. Nocturnal feeding, however, is limited to the intertidal, possibly because of predation risk on terrestrial habitat, and increases with moonlight. The amount of Zostera spp., declined dramatically after the arrival of birds, predominantly, but not entirely, due to consumption by the birds. Birds gained fat reserves in the first 2 months but then this was dramatically lost as their major food source collapsed and their daily energy intake declined. Single birds consistently fared worse than paired birds and pairs with juveniles fared better than those without suggesting a benefit of having a family to compete for food. Many birds leave the Lough at this time of reduced Zostera spp. for other sea inlets in Ireland but some remain. Body condition of the latter gradually improved in early spring and reflected a heavy reliance on terrestrial habitats, particularly farmland, to meet the birds' daily energy requirements. However, even in the period immediately before migration to the breeding ground, the birds did not regain the amount of abdominal fatness observed in November. The dramatic changes in available food and requirements of the birds drive the major changes seen in foraging behaviour as the birds evade starvation in the wintering period.

The taphonomy of Last Glacial–Interglacial Transition (LGIT) distal volcanic ash in small Scottish lakes

An extensive micro-tephrostratigraphic survey of three small lakes in the Scottish Inner Hebrides was conducted encompassing the Last Glacial–Interglacial Transition (LGIT). The lakes are highly contrasting in terms of lake area to catchment ratio, the presence or absence of stream inlets draining the catchment, and in the complexity of the catchment drainage network. A suite of distal Icelandic volcanic ashes was consistently detected in all three lakes, with three, namely Penifiler Tephra, Vedde Ash and Ashik Tephra, being common to all the lakes. These ashes were chosen to examine the taphonomic intercomparability of ash location and concentration among the lakes. Findings reveal that the part played by catchment inlets in determining ash concentration and within-basin location applies to microtephra layers as much as it does in studies of macrotephra layer thickness. The position of ash concentration maxima is also shown to vary significantly for different LGIT periods and may be a consequence of lake-level changes, especially during the early Holocene. High-resolution stratigraphic analysis through the Vedde Ash visible macrotephra at Loch Ashik reveals a high degree of complexity in taphonomic behaviour between the different geochemical components, with possible implications for the correct interpretation of the isochron position. The detection of multiple intact ash isochrons and the taphonomic processes responsible for their deposition should prove useful in future tephrostratigraphic surveys, as well as having applications within other palaeolimnological disciplines.

New design of a multi-jet target for quasi phase matching

An improved dual-gas quasi-phase matching (QPM) foil target for high harmonic generation (HHG) is presented. The target can be setup with 12 individual gas inlets each feeding multiple nozzles separated by a minimum distance of 10 μm. Three-dimensional gas density profiles of these jets were measured using a Mach-Zehnder Interferometer. These measurements reveal how the jets influence the density of gas in adjacent jets and how this leads to increased local gas densities. The analysis shows that the gas profiles of the jets are well defined up to a distance of about 300 μm from the orifice. This target design offers experimental flexibility, not only for HHG/QPM investigations, but also for a wide range of experiments due to the large number of possible jet configurations. We demonstrate the application to controlled phase tuning in the extreme ultraviolet using a 1 kHz-10 mJ-30 fs-laser system where interference between two jets in the spectral range from 17 to 30 nm was observed.