Facultative Altitudinal Movements by Mountain White-Crowned Sparrows (Zonotrichia Leucophrys Oriantha) in the Sierra Nevada

Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) winter in Mexico and often arrive in the vicinity of their breeding grounds in the Sierra Nevada well before nesting is possible. Arrival at Tioga Pass, California (elevation 3,030 m), usually occurs in early May, but residual winter snow and adverse weather can delay nesting for weeks. We used radiotelemetry to determine whether prebreeding Mountain White-crowned Sparrows engaged in weather-related altitudinal movements during the waiting period between the end of spring migration and onset of breeding during 1995-2001, with a range of residual winter snowpacks. Interannual variation in arrival date and onset of egg laying was 18 and 41 days, respectively. We tracked females for two years and males for all seven years. During spring snowstorms (which occurred in four years), radiomarked individuals moved to lower elevation sites, where they often remained for several days. Departing birds left Tioga Pass by early afternoon and returned early in the morning after storms. More frequent storms during tracking increased the likelihood of facultative altitudinal movements, but heavier residual winter snowpack did not. Warm days increased the likelihood of birds returning to Tioga Pass from low elevation. This study demonstrates that facultative altitudinal movement behavior can be a common feature of spring arrival biology in montane-breeding birds. Received 1 November 2002, accepted 30 June 2004.Integrative Biolog

Free-Living Male Mountain White-Crowned Sparrows Exhibit Territorial Aggression Without Modulating Total or Free Plasma Testosterone

In some species, expression of territorial aggression is accompanied by a rise in testosterone secretion, but in others aggressive behavior is expressed while testosterone levels remain unchanged. Corticosteroid binding globulin (CBG) binds both corticosterone and testosterone in avian plasma. Thus, increasing corticosterone may result in fluctuations in unbound ( free ) testosterone; this could result in greater biological activity of testosterone without an increase in testosterone secretion. We investigated whether such plasma interactions of testosterone, corticosterone, and CBG might result in alterations of free testosterone in male Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha). We conducted simulated territorial intrusions during incubation and compared total and free testosterone of males captured immediately following a simulated territorial intrusion with that of males captured passively. All experimental males showed aggressive behavior, but apparently did not modulate total or free testosterone relative to controls

Lutte contre Gloeosporium (album et perennans) des pommes biologiques Post-Recolte avec des produits oxidants et des eaux électrolytiques,et Pre-Recolte avec differents produits biologiques entre 2001-2004

Dans la production biologiques des pommes les pertes post-récolte causées par Gloeospo-rium album et perennans peuvent atteindre, avec des variétés sensibles comme Pinova, Topaz ou GoldRush jusqu'à 80 %. Il est connue que la thermothérapie (plonger les pommes pendant 2-3 min. dans l’eau chaude de 50-52 deg.) peut supprimer bien le développement du pathogène relativement bien. Les désavantages de la thermothérapie sont sa consommation d’énergie significative, ses hautes coûts d’investissement et finalement que les dégât latentes de G. album prove-nant du champ deviennent visible peu de jours après le traitement ce qui pouvait dévaloriser jusqu’à 30 % de la récolte. Le but de nos études c’est de trouver des méthodes de lutte contre Gloeosporium album et perennans comme alternative à la thermothérapie. Dans nos essays sur plusieurs années avec les variétés Pinova et Topas ni les produits oxi-dants (Jet5, H2O2, Nitrit, thé vert, thé de prèle ) ni l’ozone mis à l’eau (froid, 17 deg.) ont ap-porté des résultats régulièrement satisfaisants (pas de différence comparé avec les pommes non traitées). Les pertes ont atteint 60-80% après conservation et justqu’à 90 % après 10 jours de shelf-life de plus. A partir de 2004 nous avons aussi testé des eaux électrolytiques (Anostel® et Cathostel®), une technique de désinfection qui vient surtout du secteur médicinal. Elle est propre, sans formation des résidus dans les produit ou dans l’environnement. En plongeant les pommes sériellement dans ces solutions pendant 5 min. chaque, l’efficacité n’était pas aussi bonne qu’avec thermothérapie (75 % vendable après conservations) mais beaucoup meilleur (62 % vendable) qu’avec tout les autres oxidants (48 % vendable). C’est pourquoi nous essayons d’optimiser la méthode des eaux électrolytiques avec des essaies en cours de cette année. Car l’attaque des Gloeosporium sur champ peut avoir un effet tellement nocif malgré des traitements post récolte, nous avons aussi testé des stratégie de contrôle pre-récolte à partir du mois de Juillet avec des produits antagoniste (la levure Aureobasidium pullulans), KBV-Lactopéroxidase, Calcium-polysulphurique, cuivre, Calcium-Chloride (pour fortifier la cuti-cule) et Mycosin (argile acidifié). De tout les produits testés pre-récolte seulement le Mycosin donnait des résultat satisfaisant, comparable à la thermothérapie. Aussi nous avons pu prouvé qu’avec Pinova le savon de coco pour lutter contre la maladie de suie (Cocana) à un effet significativement aggravant l’incidence de Gloeosporium. Le but de nos études actuels c’est de développer des stratégies combiné pre- et post récolte (sans thermothérapie) qui n’interfèrent pas avec la lutte contre les autre maladies (suie, ta-velure, oidium) et qui se complémentent d’une façon idéale et écologique

Physiological Trade-Offs in Self-Maintenance: Plumage Molt and Stress Physiology in Birds

Trade-offs between self-maintenance processes can affect life-history evolution. Integument replacement and the stress response both promote self-maintenance and affect survival in vertebrates. Relationships between the two processes have been studied most extensively in birds, where hormonal stress suppression is down regulated during molt in seasonal species, suggesting a resource-based trade-off between the two processes. The only species found to differ are the rock dove and Eurasian tree sparrow, at least one of which performs a very slow molt that may reduce resource demands during feather growth, permitting investment in the stress response. To test for the presence of a molt–stress response trade-off, we measured hormonal stress responsiveness during and outside molt in two additional species with extended molts, red crossbills (Loxia curvirostra) and zebra finches (Taeniopygia guttata). We found that both species maintain hormonal stress responsiveness during molt. Further, a comparative analysis of all available species revealed a strong relationship between molt duration and degree of hormonal suppression. Though our results support trade-off hypotheses, these data can also be explained by alternative hypotheses that have not been formally addressed in the literature. We found a strong relationship between stress suppression and seasonality of breeding and evidence suggesting that the degree of suppression may be either locally adaptable or plastic and responsive to local environmental conditions. We hypothesize that environmental unpredictability favors extended molt duration, which in turn allows for maintenance of the hormonal stress response, and discuss implications of a possible trade-off for the evolution of molt schedules

White-Tailed Deer are a Biotic Filter During Community Assembly, Reducing Species and Phylogenetic Diversity

Community assembly entails a filtering process, where species found in a local community are those that can pass through environmental (abiotic) and biotic filters and successfully compete. Previous research has demonstrated the ability of white-tailed deer (Odocoileus virginianus) to reduce species diversity and favour browse-tolerant plant communities. In this study, we expand on our previous work by investigating deer as a possible biotic filter altering local plant community assembly. We used replicated 23-year-old deer exclosures to experimentally assess the effects of deer on species diversity (H′), richness (SR), phylogenetic community structure and phylogenetic diversity in paired browsed (control) and unbrowsed (exclosed) plots. Additionally, we developed a deer-browsing susceptibility index (DBSI) to assess the vulnerability of local species to deer. Deer browsing caused a 12 % reduction in H′ and 17 % reduction in SR, consistent with previous studies. Furthermore, browsing reduced phylogenetic diversity by 63 %, causing significant phylogenetic clustering. Overall, graminoids were the least vulnerable to deer browsing based on DBSI calculations. These findings demonstrate that deer are a significant driver of plant community assembly due to their role as a selective browser, or more generally, as a biotic filter. This study highlights the importance of knowledge about the plant tree of life in assessing the effects of biotic filters on plant communities. Application of such knowledge has considerable potential to advance our understanding of plant community assembly

Internal alignments of red versus blue discs in dark matter haloes

Large surveys have shown that red galaxies are preferentially aligned with their haloes, while blue galaxies have a more isotropic distribution. Since haloes generally align with their filaments, this introduces a bias in the measurement of the cosmic shear from weak lensing. It is therefore vitally important to understand why this difference arises. We explore the stability of different disc orientations within triaxial haloes. We show that, in the absence of gas, the disc orientation is most stable when its spin is along the minor axis of the halo. Instead when gas cools on to a disc, it is able to form in almost arbitrary orientation, including off the main planes of the halo (but avoiding an orientation perpendicular to the halo's intermediate axis). Substructure helps gasless galaxies reach alignment with the halo faster, but has less effect on galaxies when gas is cooling on to the disc. Our results provide a novel and natural interpretation for why red, gas poor galaxies are preferentially aligned with their halo, while blue, star-forming, galaxies have nearly random orientations, without requiring a connection between galaxies' current star formation rate and their merger history

Single \pi^- production in np collisions for excess energies up to 90 MeV

The quasifree reaction np\to pp\pim was studied in a kinematically complete experiment by bombarding a liquid hydrogen target with a deuteron beam of momentum 1.85 GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector $\mathbb{P}_n$ which differed from event to event. A range of almost 90 MeV excess energy above threshold was covered. Energy dependent angular distributions, invariant mass spectra as well as fully covered Dalitz plots were deduced. Sizeable $pp$ FSI effects were found as were contributions of $p$ and $d$ partial waves. The behavior of the elementary cross section $\sigma_{01}$ close to threshold is discussed in view of new cross section data. In comparison with existing literature data the results provide a sensitive test of the spectator model.Comment: 21 pages, 9 figures, 4 tables, submitted to EPJ

Optically induced coherent intra-band dynamics in disordered semiconductors

On the basis of a tight-binding model for a strongly disordered semiconductor with correlated conduction- and valence band disorder a new coherent dynamical intra-band effect is analyzed. For systems that are excited by two, specially designed ultrashort light-pulse sequences delayed by tau relatively to each other echo-like phenomena are predicted to occur. In addition to the inter-band photon echo which shows up at exactly t=2*tau relative to the first pulse, the system responds with two spontaneous intra-band current pulses preceding and following the appearance of the photon echo. The temporal splitting depends on the electron-hole mass ratio. Calculating the population relaxation rate due to Coulomb scattering, it is concluded that the predicted new dynamical effect should be experimentally observable in an interacting and strongly disordered system, such as the Quantum-Coulomb-Glass.Comment: to be published in Physical Review B15 February 200