Andreas Kaiser

Analyse von Fangzahlen im Hinblick auf die Bestandsentwicklung von Kleinvögeln nach 20jährigem Betrieb der Station Mettnau, Süddeutschland@@@Analysis of trapping figures at Mettnau station, S. Germany, with respect to the population development in small birds: a 20 years summary. 34th report of the MRI-Program

1) Im „Mettnau-Reit-Illmitz-Programm (MRI-Programm)“ der Vogelwarte Radolfzell war die Fangstation Mettnau in Süddeutschland 1991 20 Jahre in Betrieb; Daten von 119 132 Individuen (Erstfängen) von 35 Kleinvogelarten liegen vor. Die Station wird mit Japannetzen betrieben, in denen vor allem Durchzügler während des Wegzugs gefangen werden. Die jährliche Fangperiode dauert von Ende Juni bis Anfang November. Fang- und Arbeitsmethoden sind strikt und umfassend standardisiert. Die Fangzahlen werden hier im Hinblick auf Bestandsveränderungen der (hauptsächlich mitteleuropäischen) Populationen analysiert, aus denen die Fänglinge stammen. 2) Die Regressionsanalyse der jährlichen Fangzahlen ergibt für 30 der 35 Arten einen negativen Koeffizienten, der bei 14 Arten signifikant ist; von den 5 positiven Koeffizienten ist einer signifikant. Signifikante Abnahme der Fangzahlen weisen in erster Linie die Langstreckenzieher (Transsaharazieher) auf gefolgt von den Teilziehern mit hohem Standvogelanteil. Die geringste Abnahme zeigen die vor allem im Mittelmeerraum überwinternden Arten. 3) Im Vergleich zu der vorangehenden Auswertung (Berthold et al. 1986), die Daten bis 1983 erfaßte, hat sich das negative Bild der jährlichen Fangzahlen und damit der Bestandsentwicklung der zugrunde liegenden Populationen inzwischen erheblich verschlechtert. Bis 1983 wiesen die Fangzahlen der Mettnau-Station von 69% der Arten negative Koeffizienten auf, bis 1991 ist der Wert auf 85% angestiegen. Keine einzige Art zeigt eine Trendwende zu positiver Entwicklung. Die Gesamtfangzahlen aller Arten, die laufend zurückgehen, haben von der ersten zur zweiten Dekade der Untersuchungsperiode signifikant um 15% abgenommen. Besonders auffallend ist die signifikante Abnahme der Fangzahlen der Transsaharazieher seit 1980. 4) Das überaus negative Bild, das die Fangzahlen von der gegenwärtigen Bestandsentwicklung unserer Kleinvögel zeichnen, steht in Einklang mit dem, das die gegenwärtigen „Roten Listen“ von der Avifauna Mitteleuropas insgesamt vermitteln. Von einer Reihe von Arten wie Rohrschwirl, Seggenrohrsänger, Waldlaubsänger und Wendehals werden auf der Mettnau-Station nicht mehr alljährlich Individuen gefangen, und die Lücken werden sicherlich zunehmen. 5) Mögliche Unterschiede in der Bestandsentwicklung zwischen verschiedenen Populationen, einige Fehlerquellen in den Fangzahlen sowie Ursachen für Bestandsrückgänge wie die hier beschriebene Abnahme der Altvogelanteile bei Drossel- und Schilfrohrsänger werden kurz diskutiert. Bei künftigen Populationsstudien sollte der Ursachenforschung bei Bestandsrückgängen höchste Priorität zukommen. 1) The trapping station “Mettnau” in S. Germany as part of the “Mettnau-Reit-Illmitz-Program (MRI-Program)” of the Vogelwarte Radolfzell has been in operation for 20 years since 1972. During this period, 119 132 individual birds (first traps) of 35 species of small birds were captured. The station uses mist nets in which passage migrants are trapped during the autumn migratory period. The annual trapping period lasts from the end of June to the beginning of November. Trapping and working methods are strictly standardized. In this report, the trapping figures have been analyzed with respect to the development of the respective (mainly Central European) source populations of the passage migrants. 2) Regression analyses of the annual trapping totals yielded negative correlations between dates and numbers for 30 of the 35 species. The trends were statistically significant in 14 species. Among the 5 positive results only one was significant. Significant negative trends in the trapping totals are primarily found in long-distance (trans-Sahara) migrants. These were followed by partial migrants with high portions of residents. The smallest declines occurred in species that winter mainly in the Mediterranean area. 3) In comparison with the preceeding analyses (Berthold et al. 1986) in which data up to 1983 were treated, the negative picture of the annual trapping totals and thus that of the development of the respective populations has deteriorated considerably in the meantime. Up to 1983 the annual trapping totals of the Mettnau station had produced negative coefficients in 69% of the species. By 1991 this value increased to 85%. None of the species show a trend turn towards positive development. The annual trapping totals of all species which continuously decrease have declined significantly from the first to the second decade of the period of investigation by 15%. The decreases in the trapping totals of the trans-Sahara migrants are significant since 1980. 4) The extremely negative picture from these trapping figures reflect population changes which are in general agreement with the current “Red lists” of the avifauna of Central Europe. In a number of species like Savis warbler, aquatic warbler, woodwarbler and wryneck individuals are no longer even trapped annually at the Mettnau station and the gaps will certainly increase. 5) Finally, differences in the development of various populations, some sources of error within the trapping figures and some possible causes for population decline on the basis of great reed and sedge warbler data (decrease in the proportions of adult birds) are briefly discussed. It is emphasized that in future population studies investigations of the causes of population declines should have a high priority to further monitor these trends.

Nonequilibrium electron and phonon dynamics in solids absorbing a subpicosecond laser pulse

We study the temporal evolution of the distribution functions of free electron gas in metals and insulators for the case of irradiation with a laser pulse of moderate intensity. A microscopical description on the basis of time- dependent Boltzmann equations is used. The results show the sequence of excitation and relaxation of the electron gas leading eventually to thermal equilibrium. Due to photon absorption the occupation number of electron gas differs significantly from Fermi distribution. For high enough intensities about damage threshold, the energy exchange between electrons and phonos can be described with the two- temperature model. For low excitations we find a delayed energy transfer from laser-excited electron gas to lattice as compared to the two-temperature model. We obtain fluence- dependent thermalization times of the electron gas. For dielectrics we find that the essential process of free- electron generation is strong-electric-field ionization; no avalanche develops in femtosecond time reign. We propose an extended system of two rate equation taking the effect of energy dependence of impact ionization into account. This averaging approach can reproduce the evolution of free electron density in SiO2 with reasonable accuracy.

Zugdisposition mitteleuropäischer Kleinvögel: Mauser, Körpermasse, Fettdeposition und Verweildauer@@@Migratory disposition of small passerines in central Europe: moult, body mass, fat deposition, and stopover length

Data from approximately 200,000 birds caught during their stopover on southward migration at lake Constance (SW Germany) were analysed for the extent of migratory disposition. Variation in migration patterns (the increase in number of arriving birds) correlates well with the onset of migratory disposition in a sub-sample of approximately 13,000 first-captures of 58 species, mainly warblers (Acrocephalus, Sylvia, andPhylloscopus), tits, and thrushes. 72 % of all birds partially or fully renewed their body feathers during the study period, indicating that most birds were in the early stage of their migration. Body condition changed significantly with migratory disposition, thus fat deposition increased with decreasing moult intensity, whereas body mass of first captures increased very slowly over time in some species. Differences in ecophysiological parameters were tested among long-, intermediate- and short-distance migrants as well as between the pre-migration and the migration period. Long-distance migrants moulted fast, had a minimum stopover period of only 4.8 days and were considerably fatter than short-distance migrants. During migration 90 % of all individuals were captured only once. These “fast passage migrants” or transients can be distinguished from “longer resting birds” using captures if several factors including moult progress, moult intensity, fat deposition, season, capture time and habitat are considered. A discriminant analysis revealed that age and wing length also had a significant influence on the resting strategy in some populations. Combining results from multi-factor analyses and theoretical flight distance estimates variation in resting strategy supports a hypothesis of small stages and long stopover periods in most individuals and species. Zur Beantwortung der bislang offenen Frage, wie mitteleuropäische Rastplätze von Kleinvögeln verschiedener Arten zur Zugzeit zur Zugvorbereitung und als Zwischenstopp genutzt werden, wurden Fang-Wiederfangdaten, ökologische Daten und am Vogel gemessene morphologisch-physiologische Parameter ausgewertet, so die Beziehung zwischen Körpermasse, Mauser und Fettdeposition einschließlich saisonaler Variation. Annähernd 200 000 Fänge von 58 Arten wurden untersucht, vor allem Rohrsänger, Grasmücken, Laubsänger und Drosseln. Mit Hilfe von Diskriminanzanalysen wurde gezeigt, daß schnell durchziehende Vögel im Vergleich zu Rastvögeln deutlich fetter und geringfügig schwerer sind, später im Herbst durchziehen, weniger mausern und teilweise größer und älter sind. Teilweise bestehen auch Unterschiede in der Habitatwahl. Bei 72 % aller Vögel wurde von Ende Juni bis Anfang November auf der Mettnau Teilmauser (Kleingefiedermauser) nachgewiesen. Großgefiedermauser trat im allgemeinen selten auf. Einzelne Vögel mauserten ihr Kleingefieder z. T. länger als 3 Monate, andere, besonders Langstreckenzieher, nur etwa einen Monat lang. Die Fettdeposition setzte mit abnehmender Mauserintensität ein, teilweise bei Langstreckenziehern schon sehr früh. Zur Zugzeit mauserten sehr fette Vögel nicht mehr oder nur wenige Federn, dagegen Vögel mit geringer Fettdeposition und lange rastende Vögel stark. Die minimale Rastdauer betrug durchschnittlich 6,2 Tage für alle Arten und 4,8 Tage für Langstreckenzieher. Der allgemeine Zugbeginn — der saisonale Anstieg von Erstfangzahlen im Fangmuster — deckte sich mit dem Auftreten fetter Vögel und der Abnahme in der Kleingefiedermauser-Intensität. Im saisonalen Verlauf nimmt bei allen untersuchten Arten nach der Brutzeit die Mauserintensität des Kleingefieders zu. Eine deutliche Zunahme in der Fettdeposition wird erst bei Abnahme der Mauserintensität beobachtet. Die Körpermasse stieg bei manchen Arten mit der Fettdeposition, bei anderen (z. B. beim Rotkehlchen) dagegen auch bei fetten Vögeln kaum. Die Schätzwerte der sichtbaren Fettdeposition lagen für Langstreckenzieher höher als für Mittelstreckenzieher und diese höher als für Standvögel. Insgesamt sind die Durchschnittswerte zur Zugzeit niedrig und nur doppelt so hoch wie zur Vorzugzeit, in der keine Fettdepots angelegt werden. Der relative Fettgehalt beträgt zur Zugzeit im Mittel 25 % der fettfreien Trockenmasse, nur 2 % aller Fänge sind sehr fett. Nach der Rast erhöht sich die theoretische Zugstreckenleistung im Mittel um 31 km auf 166 km. Eine geringe Zugstreckenleistung macht entweder kurze Zugetappen oder längere Rast wahrscheinlich.

Irradiation of solids with subpicosecond laser pulses: excitation and relaxation dynamics of electrons and phonons

Irradiation of metals and dielectrics with subpicosecond laser pulses reveals a variety of different microscopic processes compared to longer pulses. We choose a transport theoretical description of electrons and phonons, which allows us to investigate the contribution of particular collision processes on macroscopic material response, even for highly nonequilibrium subsystems where a hydrodynamic description fails. The absorption of laser energy is described by photon- absorption of free electrons with assistance of phonon collisions. We considered relaxation of the electron gas by electron-electron and electron-phonon collisions. In the case of a dielectric, terms for multiphoton ionization and impact ionization are included. A resulting system of coupled time- dependent Boltzmann equations is solved numerically. For SiO2 as an example of dielectrics we calculate changes in occupation numbers of electrons and phonons, respectively, determining the sequence of excitation and relaxation of the subsystems under ultrashort laser pulse irradiation. It is shown that the essential process of free-electron generation is multiphoton ionization. Additionally, we investigate polarization effects for the case of irradiation of metals. Using parameters for gold we find anisotropic absorption of laser energy, which depends on polarization of the electric field and material parameters as well as on photon energy of irradiating laser light.

Nonparametric detection of dependences in stochastic point processes

A new, parameter-free approach based on information theoretical tools is presented which allows the detection of dependences in the dynamics between two point processes. The crucial point is the definition of sequences of inter-event intervals between the events of two stochastic point processes where these sequences are ordered to only one common time index. This is an enhancement of the concept of event intervals of a single point process and makes the analysis of the process dynamics of more than one point processes possible. An application of this method is also illustrated using a model consisting of two synaptically coupled Hindmarsh–Rose neurons.

Excitation and relaxation dynamics of electrons and phonons in solids absorbing subpicosecond laser pulses

The distribution function of free electron gas in metals and insulators for the case of irradiation with a laser pulse of moderate intensity is calculated. A microscopical description on the basis of time-dependent Boltzmann equations is used. For the metal, photon absorption by free electrons, electron-electron collisions and electron-phonon collisions are considered each by a corresponding collision integral. In dielectrics, additional terms for two ionization processes (strong-electric-field ionization and impact ionization) are included. We choose aluminum as a representative of a metal and SiO2 for modeling an insulator. The results show the sequence of excitation and relaxation of the electron gas. Due to photon absorption the occupation number of electron gas differs significantly from Fermi distribution. For metals we show that electron thermalization to a Fermi distribution occurs rapidly within less than hundred femtosecond after irradiation ended. For dielectrics we find that for pulses shorter than about 100 fs, impact ionization is negligible in comparison with strong-electric-field ionization. We shown that in this case impact ionization can not be described by simple rate equations.

Microscopical dynamics in solids absorbing a subpicosecond laser pulse

Microscopic collision processes in solids occur on femtosecond time scales. A description of materials response to laser irradiation on this time scales should take these processes explicitly into account. Averaging descriptions are not applicable from the first. We calculate the distribution function of free electron gas in metals and insulators for the case of irradiation with a laser pulse of moderate intensity. A microscopical description on the basis of time-dependent Boltzmann equations is used. For the metal, photon absorption by free electrons, electron-electron collisions and electron-phonon collisions are considered each by a corresponding collision integral. In dielectrics, additional terms for two ionization processes (strong-electric-field ionization and impact ionization) are included. With this model, describing explicitly materials transient behavior, we are able to check the applicability of common averaging equations. For metals irradiated with sufficient high intensities about and above damage threshold the energy exchange between electrons and phonons can be described with the two temperature model, whereas for low excitation the non- equilibrium in the electron gas affects the electron-phonon coupling. For dielectrics we show that the commonly used rate equation for collisional ionization is not applicable for pulse durations below hundred femtoseconds. We propose an extended system of two rate equations taking the effect of energy dependence of impact ionization into account. This averaging approach can reproduce the evolution of free electron density in SiO2 with reasonable accuracy.