Search

Nest predation is the primary cause of nest failure in most ground-nesting bird species. Investigations of relationships between nest predation rate and habitat usually pool different predator species. However, such relationships likely depend on the specific predator involved, partly because habitat requirements vary among predator species. Pooling may therefore impair our ability to identify conservation-relevant relationships between nest predation rate and habitat. We investigated predator-specific nest predation rates in the forest-dependent, ground-nesting wood warbler Phylloscopus sibilatrix in relation to forest area and forest edge complexity at two spatial scales and to the composition of the adjacent habitat matrix. We used camera traps at 559 nests to identify nest predators in five study regions across Europe. When analyzing predation data pooled across predator species, nest predation rate was positively related to forest area at the local scale (1000 m around nest), and higher where proportion of grassland in the adjacent habitat matrix was high but arable land low. Analyses by each predator species revealed variable relationships between nest predation rates and habitat. At the local scale, nest predation by most predators was higher where forest area was large. At the landscape scale (10,000 m around nest), nest predation by buzzards Buteo buteo was high where forest area was small. Predation by pine mar- tens Martes martes was high where edge complexity at the landscape scale was high. Predation by badgers Meles meles was high where the matrix had much grassland but little arable land. Our results suggest that relationships between nest predation rates and habitat can depend on the predator species involved and may differ from analyses disregarding predator identity. Predator-specific nest predation rates, and their relationships to habitat at different spatial scales, should be considered when assessing the impact of habitat change on avian nesting success.

Differences in population trends across a species’ breeding range are ultimately linked to variation in demographic rates. In small songbirds, demographic rates related to fecundity typically have strong effects on population trends. Populations of a forest songbird, the wood warbler Phylloscopus sibilatrix, have been declining in many but not all regions of the European breeding range. We investigated if clutch size, hatching rate, nest survival and number of fledglings vary across Europe, and if nest survival is related to differences in the regionally dominant nest predator class (birds versus mammals). From 2009 to 2020, we monitored 1896 nests and used cameras at a subsample of 645 nests in six study regions: the United Kingdom (mid-Wales, Dartmoor, the New Forest), Germany (Hessen), Switzerland (Jura mountains) and Poland (Białowieża National Park). Number of fledglings was lowest in the New Forest (1.43 ± CI 0.23), intermediate in Jura (2.41 ± 0.31) and Białowieża (2.26 ± 0.24) and highest in mid-Wales (3.02 ± 0.48) and Dartmoor (2.92 ± 0.32). The reason for low reproductive success in the New Forest, Jura and Białowieża was low nest survival, and large clutch sizes in Białowieża did not compensate for high nest losses. High reproductive success in mid-Wales and Dartmoor was due to high nest survival and large clutch sizes. Overall predation rates were similar everywhere despite variation between the regions in the dominant nest predator class. Unsuccessful nests in mid-Wales were mainly predated by birds; in Dartmoor, the New Forest, Hessen and Jura similarly by birds and mammals; and in Białowieża exclusively by mammals. Regional reproductive success does not match the population trends recently reported for the wood warbler in the six study regions (i.e. high reproduction ≠ positive trend). Annual survival may be a decisive factor, but it is difficult to quantify for a nomadic species such as the wood warbler that rarely returns to the same breeding locations.

The Pre-Chamber spark plug, already in its most simple configuration, allows a cycle fuel consumption reduction of 2-3% (WLTC) by enabling a significant compression ratio increase due to its huge knock mitigation effect. This benefit can be strongly extended in the homogeneous lean burn operation mode with very low nitrogen oxide emissions by a novel approach of injecting a well prepared fuel-air-mixture inside the Pre-Chamber. An increase of the engine compression ratio allows further the development of a new combustion process referred as the Pre-Chamber supported self-ignition process, which enable an increased thermodynamic efficiency at part load operating points of a gasoline engine. The development of a suitable Pre-Chamber ignition system requires the technical understanding of the Pre-Chamber geometry parameters on the combustion process. The impact of the overflow channel design on the flame propagation and ignition of the fuel-air mixture inside the main chamber must be understood in greater detail. This in turn requires a high-fidelity combustion model which is capable of predicting the impact of the overflow channel geometry on e.g. flame extinction, radical recombination on the walls of the Pre-Chamber orifice and finally the behavior of main chamber inflammation regardless of the Pre-Chamber ignition regime. Focus of this work is to discuss the impact of the Pre-Chamber geometry onto the inflammation and early flame propagation inside the main combustion chamber by means of experiments in an optical high pressure vessel under simplified boundary conditions. As a basis, the simultaneous high speed measurement of Schlieren and OH* chemiluminescence serve as a fundamental means to analyze ignition performance and early flame propagation in order to develop and validate an accurate combustion model. Initially, the general impact of the chamber pressure will be discussed emphasizing specifically on the differences between certain Pre-Chamber layouts and the conventional ignition system onto flame speed and ignition probability. Furthermore, variations of e.g. the number of overflow holes, the orifice diameter and the volume of the Pre- Chamber aids to identify the most relevant parameters responsible for flame extinction and combustion performance inside the main chamber.

Der Einsatz digitaler Werkzeuge beeinflusst den Mathematikunterricht auf vielen Ebenen. Lerman (2013, S.41) stellt heraus, dass sich die Forschung in diesem Bereich jedoch meist auf die Einsatzmöglichkeiten, die Unterrichtsplanung und praktische Umsetzung richtet. Die potenziell tiefgreifenden Veränderungen des Lernens von Mathematik und der gelernten Mathematik wurden dabei noch nicht in ausreichendem Maße tiefergehend analysiert. In diesem Artikel sollen zunächst die theoretische Fundierung der Fragestellung dargestellt und eine Studie zur explorativen Untersuchung mit ersten Beobachtungen vorgestellt werden.