Predation on meadowbirds in The Netherlands : results of a four-year study

Meadowbird populations in The Netherlands are under great pressure. Recently, predation is named increasingly often as one of the key factors in contributing to the declines. A four-year research project (2001-2005) aimed to collect (as yet mostly nonexisting) data to provide a factual basis for this discussion. A country-wide inventory based on data for wader nests found by volunteers who mark nests for their protection from grazing/mowing indicated that above-average predation losses are found predominantly in the half-open landscapes of northern and eastern Netherlands, but also locally in the low-lying open grasslands which are the key areas for meadowbirds. Nest predation has increased in recent years, but the same is true for agricultural losses, at least in areas where no nest-protection takes place. At a local scale, predation losses vary greatly from area to area and from year to year. Temperature loggers in nest showed that diurnal and nocturnal predators contribute equally in total predation losses up to 50%, but higher predation losses are mainly caused by nocturnal predators. As many as 10 animal species were identified as nest predators on nests under surveillance with video cameras. Chick survival, investigated using radiotelemetry, was very low. About 60-80% were lost by predation, 5-15% by agricultural activities and 10-15% to all kind of other losses. At least 15 predator species were implied, with an apparently larger share taken by birds (notably Buzzard (16%) and Grey Heron (7-18%)) than mammals, with one exception: stoat (16%). Of the most-discussed predator species, Carrion Crows were W. Teunissen et al. Osnabrücker Naturwiss. Mitt. 32 2006 138 remarkably rarely involved in both nest and chick predation, while Red Foxes take a large toll of clutches in some areas, but not in others. Of all losses during the reproductive cycle about 75% and 60% was due to predation in Lapwing and Black-tailed Godwit respectively. Predation on chicks by birds had the largest effect on total breeding success, but at the same time elimination of this loss factor (if at all possible) alone would not be sufficient to establish a self-sustaining population. Predation seems to have become a factor of importance in some areas, in combination with already existing other losses. Our findings suggest that solutions to predation problems probably have to be found in locally/regionally targeted, specific action on multiple fronts rather than countrywide measures.Die Wiesenvogelpopulationen in den Niederlanden sind in den letzten Jahrzehnten stark unter Druck geraten. In jüngster Zeit wird zunehmend die Prädation als einer der Hauptfaktoren für den zu beobachtenden Bestandsrückgang genannt. Aus diesem Grund ist ein Forschungsprojekt mit dem Titel „Wiesenvögel und Prädation“ (2001 – 2005) initiiert worden, das sich zum Ziel gesetzt hat, umfangreiches Datenmaterial als Grundlage für die fachliche Auseinandersetzung mit diesem Thema zu sammeln. Der erste Schritt beinhaltete eine Auswertung landesweiter Daten zu prädationsbedingten Gelegeverlusten bei Wiesenlimikolen. Die von Freiwilligen erhobenen Daten zeigen, dass überdurchschnittlich hohe Verluste vor allem in halboffenen Landschaften im Norden und Osten der Niederlande auftreten. Allerdings wurden lokal auch höhere Verluste in tiefer gelegenen Marsch- und Niederungsgebieten, den Hauptverbreitungszentren niederländischer Wiesenvogelpopulationen, gefunden. Insgesamt betrachtet hat die Prädation von Gelegen in den vergangenen Jahren zugenommen. Gleiches gilt allerdings auch für landwirtschaftlich bedingte Gelegeverluste in solchen Gebieten, in denen kein aktiver Gelegeschutz betrieben wird. Auf lokaler Ebene zeigten die prädationsbedingten Gelegeverluste starke Schwankungen sowohl zwischen einzelnen Gebieten als auch zwischen aufeinander folgenden Jahren. Zur Identifizierung von Gelegeprädatoren wurden Thermologger und Videokameras eingesetzt. Bei Verlusten von insgesamt bis zu 50 % aller auftretenden Gelege, hielten sich tag- und nachtaktive Räuber als Täter annähernd die Waage. Traten dagegen höhere Gelegeverluste auf, so waren daran in erster Linie nachtaktive Raubsäuger beteiligt. Über die eingesetzte Videotechnik konnten insgesamt 10 verschiedene Gelegeprädatoren (6 Säugetier- und 4 Vogelarten) nachgewiesen werden. Die Kükenverluste bei Kiebitz und Uferschnepfe wurden mittels Radiotelemetrie untersucht. Die Überlebensrate der Küken war insgesamt sehr gering: 60 – 80% der Kükenverluste gingen auf Prädation zurück, 5 - 15 % entfielen auf landwirtschaftliche Einflüsse. Alle übrigen Verlustursachen machten 10 – 15 % der Verluste aus. Mindestens 15 Säugetier- und Vogelarten konnten bislang als Kükenprädatoren nachgewiesen werden, wobei offensichtlich Vögel einen größeren Einfluss hatten (u.a. Mäusebussard: 16%, Graureiher: 7 - 18% aller Verluste) als Raubsäuger. Eine Ausnahme stellt das Hermelin dar, das für ca. 16 % aller Verluste verantwortlich war. Die Rabenkrähe, die immer wieder als Gelege- und Kükenprädator genannt wird, spielte in beiden Bereichen (hier: Gelege- und Kükenprädation) nur eine untergeordnete Rolle. Der Rotfuchs dagegen dominierte in vielen, wenn auch längst nicht allen Gebieten als Gelegeprädator. Die Kombination aller gesammelten Gelege- und Kükendaten ermöglichte eine Abschätzung der Bedeutung einzelner Verlustursachen für den Reproduktionserfolg. Insgesamt betrugen die Prädationsverluste während der Brutperiode ca. 75 % beim Kiebitz und ca. 60 % bei der Uferschnepfe. Die Kükenverluste durch Vögel schlugen dabei in Bezug auf den Bruterfolg am stärksten zu Buche. Allerdings würde selbst eine komplette Eliminierung dieses Verlustfaktors (wenn überhaupt möglich) nicht zu einem ausreichenden Reproduktionserfolg führen. Die vorliegenden Ergebnisse verdeutlichen an, dass die Prädation in Kombination mit anderen, bereits vorhandenen Verlustursachen zu einem wesentlichen Populationsfaktor in verschiedenen Wiesenvogelgebieten geworden ist. Unsere Befunde legen ferner den Schluss nahe, dass in Wiesenvogelgebieten mit „Prädationsproblemen“ Lösungen nur vor Ort, also auf lokaler/regionaler Ebene, gefunden werden können

Quantum phase transitions in matrix product systems

We investigate quantum phase transitions (QPTs) in spin chain systems characterized by local Hamiltonians with matrix product ground states. We show how to theoretically engineer such QPT points between states with predetermined properties. While some of the characteristics of these transitions are familiar, like the appearance of singularities in the thermodynamic limit, diverging correlation length, and vanishing energy gap, others differ from the standard paradigm: In particular, the ground state energy remains analytic, and the entanglement entropy of a half-chain stays finite. Examples demonstrate that these kinds of transitions can occur at the triple point of `conventional' QPTs.Comment: 5 pages, 1 figur

Flight testing and simulation of an F-15 airplane using throttles for flight control

Flight tests and simulation studies using the throttles of an F-15 airplane for emergency flight control have been conducted at the NASA Dryden Flight Research Facility. The airplane and the simulation are capable of extended up-and-away flight, using only throttles for flight path control. Initial simulation results showed that runway landings using manual throttles-only control were difficult, but possible with practice. Manual approaches flown in the airplane were much more difficult, indicating a significant discrepancy between flight and simulation. Analysis of flight data and development of improved simulation models that resolve the discrepancy are discussed. An augmented throttle-only control system that controls bank angle and flight path with appropriate feedback parameters has also been developed, evaluated in simulations, and is planned for flight in the F-15

Structural analysis of impact-related deformation in the collar rocks of the Vredefort Dome, South Africa

The Vredefort Dome is located southwest of Johannesburg, South Africa, and represents the deeply eroded remnant of the central uplift of the world’s largest known impact structure, with an estimated diameter of ~300 km. The Vredefort impact structure is also the oldest known impact structure on Earth (~2.02 Ga). The Vredefort Dome comprises an ~40 km wide core of Archaean basement gneisses and an ~20 km wide collar of subvertical to overturned Late Archaean to Palaeoproterozoic supracrustal strata. This project presents the results of Landsat-TM and aerial photograph analysis, as well as field mapping of Witwatersrand Supergroup metasedimentary strata in the collar of the Vredefort Dome. The aim of this study was to investigate the structures (such as folds, faults, fractures), at all scales, and other deformation features (such as shatter cones and pseudotachylitic breccias) in the field area, and to establish geometric and temporal relationships between these features with regard to the impact cratering process. This study revealed a highly heterogeneous internal structure of the collar involving folds, faults, fractures and melt breccias that are interpreted as the product of shock deformation and central uplift formation during the Vredefort impact event. Broadly radially-oriented symmetric and asymmetric folds, with wavelengths from tens of metres to kilometres, and conjugate radial to oblique faults with strike-slip displacements of, typically, tens to hundreds of metres accommodated tangential shortening of the collar of the dome that decreased from ~17 %, at a radial distance from the dome centre of 21 km, to <5 % at a radial distance of 29 km. Ubiquitous shear fractures containing pseudotachylitic breccia, particularly in the metapelitic units, display variable local slip senses consistent with either tangential shortening or tangential extension; however, it is uncertain whether they formed at the same time as the larger faults during the rise of the central uplift or earlier, during the shock compression phase of cratering. Contrary to the findings about shatter cones of some earlier workers in the Vredefort structure, the Vredefort cone fractures do not show uniform apex orientations at any given outcrop, nor do small cones show a pattern consistent with the previously postulated “master cone” concept. The model of simple back-rotation of the strata to a horizontal pre-impact position also does not lead to a uniform centripetal-upward orientation of the cone apices. Striation patterns on the cone surfaces are variable, ranging from typically diverging, i.e., branching off the cone apex, to subparallel to parallel on almost flat surfaces. Striation angles on shatter cones do not increase with distance from the crater centre, as suggested previously. Instead, individual outcrops present a range of such striation angles, and a more irregular distribution of striation angle values with regard to the distance from the crater centre suggests localised controls involving the nature and shape of various heterogeneities in the target rock on this aspect of cone morphology. On the basis of the observations made during this study on small-scale structures in the collar of the Vredefort Dome, the relationship of shatter cones with curviplanar fractures (multipli-striated joint sets - MSJS) is confirmed. Pervasive, metre-scale tensile fractures crosscut shatter cones and appear to have formed after the closely-spaced MSJ-type fractures. The results of this study indicate that none of the existing models is able to explain all characteristics of shatter cones fully; therefore, a combination of aspects of the different models may currently be the best possible way to explain the formation and origin of shatter cones, and the formation of the related MSJ and their characteristic aspects (e.g., curviplanar shape, melt formation, etc.). The observed variety of shatter cone orientations, surface morphology and striation geometry in the dome concurs broadly with the results of some previous studies. The abundance of striated surfaces along closely-spaced sets of fractures (MSJ) observed in this study can be reconciled with reflection/scattering of a fast propagating wave at heterogeneities in the target rocks, as proposed by recent studies. This would mean that closely-spaced fractures and shatter cones were not formed during shock compression, as widely postulated in the past, but immediately after the passage of the shock wave, by the interference of the scattered elastic wave and the tensional hoop stress that develops behind the shock front. In addition to shatter cones, quartzite units show two other fracture types – a centimetre-spaced rhomboidal to orthogonal type that may be the product of shock-induced deformation and related to the formation of shatter cones, and later joints accomplishing tangential and radial extension. The occurrence of pseudotachylitic breccia within some of these later joints confirms the general impact timing of these features. Pseudotachylitic breccias in the collar rocks occur as up to several centimetre-wide veins with variable orientations to the bedding and as more voluminous pods and networks in zones of structural complexity, such as the hinges of large-scale folds and along large-scale faults, as well as locally, at lithological interfaces. In places, tension gash arrays along thin veins are observed indicating that movement occurred along these planes. Initial cooling calculations for pseudotachylitic breccias of different widths and compositions (metapelite or quartzite) suggest that thick veins (<10 cm) could have stayed molten over the entire duration of crater development (at least 10 minutes), making it possible for shock-induced melts to intrude dilational sites, such as fold hinges and extensional fractures, during the formation and subsequent collapse of the central uplift. Intrusion of such melts may also have lubricated movements along brittle and ductile structures. Thus, the presence of both shock- and friction-generated melts is likely in the collar of the Vredefort Dome. Based on the spatial and geometric relationship between the structures and other deformation features observed in the collar rocks of the Vredefort Dome, it is possible to establish a temporal sequence of deformation events. Shatter cones and related closely-spaced fractures were formed during the contact/compression phase of the cratering process. The formation of at least some shock-induced pseudotachylitic breccia also belongs into this phase. Large-scale folds and faults and friction-generated melts can be related to the initial formation of the central uplift and extensional joints to the subsequent collapse of the central uplift

Manure Handling System Attributes Impact on Manure Management Investment Decisions: A Random Utility Model Approach

Replaced with revised version of paper 07/22/08.Farm Management, Livestock Production/Industries,

Market Segments and Farmer Preferences for Financial Record Systems

farm management, accounting systems, Farm Management,

PEPS as unique ground states of local Hamiltonians

In this paper we consider projected entangled pair states (PEPS) on arbitrary lattices. We construct local parent Hamiltonians for each PEPS and isolate a condition under which the state is the unique ground state of the Hamiltonian. This condition, verified by generic PEPS and examples like the AKLT model, is an injective relation between the boundary and the bulk of any local region. While it implies the existence of an energy gap in the 1D case we will show that in certain cases (e.g., on a 2D hexagonal lattice) the parent Hamiltonian can be gapless with a critical ground state. To show this we invoke a mapping between classical and quantum models and prove that in these cases the injectivity relation between boundary and bulk solely depends on the lattice geometry.Comment: 8 page

Entanglement versus Bell violations and their behaviour under local filtering operations

We discuss the relations between the violation of the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality for systems of two qubits on the one side and entanglement of formation, local filtering operations, and the entropy and purity on the other. We calculate the extremal Bell violations for a given amount of entanglement of formation and characterize the respective states, which turn out to have extremal properties also with respect to the entropy, purity, and several entanglement monotones. The optimal local filtering operations leading to the maximal Bell violation for a given state are provided, and the special role of the resulting Bell diagonal states in the context of Bell inequalities is discussed