Home range and habitat use of little owl (Athene noctua) in an agricultural landscape in coastal Catalonia, Spain

Área de campeo y uso del hábitat del mochuelo europeo (Athene noctua) en un paisaje agrícola de la costa de Cataluña, España El paisaje agrícola en Cataluña ha sufrido una profunda transformación en las últimas décadas, tal y como ha ocurrido en gran parte de Europa. La reforestación y especialmente el desarrollo urbanístico han reducido las tierras agrícolas y con ello se ha perdido hábitat adecuado para especies como el mochuelo europeo (Athene noctua). Los alrededores de la ciudad de Mataró, a orillas del Mar Mediterráneo, son un buen ejemplo de este cambio, pero todavía acogen una población de mochuelos allí donde se da actividad agrícola. Entre noviembre de 2007 y principios de agosto de 2008 se siguieron semanalmente con telemetría tres mochuelos residentes en este entorno agrícola periurbano. La media del área de campeo ± DE estimada con el polígono convexo mínimo (MCP100) fue de 10,9 ± 5,5 ha, y de 7,4 ± 3,8 ha, con el estimador de Kernel 95% (K95). Las áreas de campeo de las parejas vecinas se solapaban un 18,4% (MCP100) o un 6% (K95). Las áreas de campeo entre temporadas variaron a lo largo del seguimiento y llegaron a un máximo entre marzo y principios de agosto, aunque éstas siempre albergaron la zona del nido. Las pequeñas manchas arboladas se asociaron a áreas de reposo y nidificación, donde las cavidades naturales de los algarrobos (Ceratonia siliqua) eran importantes. Cuando los mochuelos se detectaron en los campos, fue en cultivos recién cosechados o replantados. Los tres mochuelos criaron con éxito. Palabras clave: Mochuelo europeo, Athene noctua, Telemetría, Conservación, Área vital, Área de campeo, Uso del hábitat, Paisaje agrícola.In recent decades agricultural landscapes in Catalonia have undergone a profound transformation as in most of Europe. Reforestation and urban development have reduced farmland and therefore the availability of suitable habitat for some bird species such as the little owl (Athene noctua). The outskirts of the city of Mataró by the Mediterranean Sea exemplify this landscape change, but still support a population of little owl where agriculture is carried out. Three resident little owls were monitored with telemetry weekly from November 2007 until the beginning of August 2008 in this suburban agricultural landscape. Mean home range ± SD was 10.9 ± 5.5 ha for minimum convex polygon (MCP100) and 7.4 ± 3.8 ha for Kernel 95% probability function (K95). Home ranges of contiguous neighboring pairs overlapped 18.4% (MCP100) or 6% (K95). Home range varied among seasons reaching a maximum between March and early August but always included the nesting site. Small forested patches were associated with roosting and nesting areas where cavities in carob trees (Ceratonia siliqua) were important. When foraging in crop fields, the owls typically fed where crops had recently been harvested and replanted. All three owls bred successfully. Key words: Little owl, Athene noctua, Telemetry, Conservation, Home range, Habitat use, Agricultural landscapeÁrea de campeo y uso del hábitat del mochuelo europeo (Athene noctua) en un paisaje agrícola de la costa de Cataluña, España El paisaje agrícola en Cataluña ha sufrido una profunda transformación en las últimas décadas, tal y como ha ocurrido en gran parte de Europa. La reforestación y especialmente el desarrollo urbanístico han reducido las tierras agrícolas y con ello se ha perdido hábitat adecuado para especies como el mochuelo europeo (Athene noctua). Los alrededores de la ciudad de Mataró, a orillas del Mar Mediterráneo, son un buen ejemplo de este cambio, pero todavía acogen una población de mochuelos allí donde se da actividad agrícola. Entre noviembre de 2007 y principios de agosto de 2008 se siguieron semanalmente con telemetría tres mochuelos residentes en este entorno agrícola periurbano. La media del área de campeo ± DE estimada con el polígono convexo mínimo (MCP100) fue de 10,9 ± 5,5 ha, y de 7,4 ± 3,8 ha, con el estimador de Kernel 95% (K95). Las áreas de campeo de las parejas vecinas se solapaban un 18,4% (MCP100) o un 6% (K95). Las áreas de campeo entre temporadas variaron a lo largo del seguimiento y llegaron a un máximo entre marzo y principios de agosto, aunque éstas siempre albergaron la zona del nido. Las pequeñas manchas arboladas se asociaron a áreas de reposo y nidificación, donde las cavidades naturales de los algarrobos (Ceratonia siliqua) eran importantes. Cuando los mochuelos se detectaron en los campos, fue en cultivos recién cosechados o replantados. Los tres mochuelos criaron con éxito. Palabras clave: Mochuelo europeo, Athene noctua, Telemetría, Conservación, Área vital, Área de campeo, Uso del hábitat, Paisaje agrícola

Lattice dynamics and phonon softening in Ni-Mn-Al Heusler alloys

Inelastic and elastic neutron scattering have been used to study a single crystal of the Ni$_{54}$Mn$_{23}$Al$_{23}$ Heusler alloy over a broad temperature range. The paper reports the first experimental determination of the low-lying phonon dispersion curves for this alloy system. We find that the frequencies of the TA$_2$ modes are relatively low. This branch exhibits an anomaly (dip) at a wave number $\xi_{0} ={1/3}\approx 0.33$, which softens with decreasing temperature. Associated with this anomalous dip at $\xi_{0}$, an elastic central peak scattering is also present. We have also observed satellites due to the magnetic ordering.Comment: 6 pages, 6 figures. Accepted for publication in the Physical Review

Premartensitic transition driven by magnetoelastic interaction in bcc ferromagnetic Ni2MnGaNi_{2}MnGa

We show that the magnetoelastic coupling between the magnetization and the amplitude of a short wavelength phonon enables the existence of a first order premartensitic transition from a bcc to a micromodulated phase in $Ni_{2}MnGa$. Such a magnetoelastic coupling has been experimentally evidenced by AC susceptibility and ultrasonic measurements under applied magnetic field. A latent heat around 9 J/mol has been measured using a highly sensitive calorimeter. This value is in very good agreement with the value predicted by a proposed model.Comment: 4 pages RevTex, 3 Postscript figures, to be published in Physical Review Letter

Temperature and magnetic field dependences of the elastic constants of Ni-Mn-Al magnetic Heusler alloys

We report on measurements of the adiabatic second order elastic constants of the off-stoichiometric Ni$_{54}$Mn$_{23}$Al$_{23}$ single crystalline Heusler alloy. The variation in the temperature dependence of the elastic constants has been investigated across the magnetic transition and over a broad temperature range. Anomalies in the temperature behaviour of the elastic constants have been found in the vicinity of the magnetic phase transition. Measurements under applied magnetic field, both isothermal and variable temperature, show that the value of the elastic constants depends on magnetic order, thus giving evidence for magnetoelastic coupling in this alloy system.Comment: 7 pages, 5 figures. Accepted for publication in Physical the Review

On the athermal character of structural phase transitions

The significance of thermal fluctuations on nucleation in structural first-order phase transitions has been examined. The prototype case of martensitic transitions has been experimentally investigated by means of acoustic emission techniques. We propose a model based on the mean first-passage time to account for the experimental observations. Our study provides a unified framework to establish the conditions for isothermal and athermal transitions to be observed.Comment: 5 pages, 4 figures, accepted in Phys. Rev. Let

A multicaloric cooling cycle that exploits thermal hysteresis

The giant magnetocaloric effect, in which large thermal changes are induced in a material on the application of a magnetic field, can be used for refrigeration applications, such as the cooling of systems from a small to a relatively large scale. However, commercial uptake is limited. We propose an approach to magnetic cooling that rejects the conventional idea that the hysteresis inherent in magnetostructural phase-change materials must be minimized to maximize the reversible magnetocaloric effect. Instead, we introduce a second stimulus, uniaxial stress, so that we can exploit the hysteresis. This allows us to lock-in the ferromagnetic phase as the magnetizing field is removed, which drastically removes the volume of the magnetic field source and so reduces the amount of expensive Nd-Fe-B permanent magnets needed for a magnetic refrigerator. In addition, the mass ratio between the magnetocaloric material and the permanent magnet can be increased, which allows scaling of the cooling power of a device simply by increasing the refrigerant body. The technical feasibility of this hysteresis-positive approach is demonstrated using Ni-Mn-In Heusler alloys. Our study could l

Colossal barocaloric effects near room temperature in plastic crystals of neopentylglycol.

There is currently great interest in replacing the harmful volatile hydrofluorocarbon fluids used in refrigeration and air-conditioning with solid materials that display magnetocaloric, electrocaloric or mechanocaloric effects. However, the field-driven thermal changes in all of these caloric materials fall short with respect to their fluid counterparts. Here we show that plastic crystals of neopentylglycol (CH3)2C(CH2OH)2 display extremely large pressure-driven thermal changes near room temperature due to molecular reconfiguration, that these changes outperform those observed in any type of caloric material, and that these changes are comparable with those exploited commercially in hydrofluorocarbons. Our discovery of colossal barocaloric effects in a plastic crystal should bring barocaloric materials to the forefront of research and development in order to achieve safe environmentally friendly cooling without compromising performance

First-principles study of lattice instabilities in the ferromagnetic martensite Ni2_2MnGa

The phonon dispersion relations and elastic constants for ferromagnetic Ni$_2$MnGa in the cubic and tetragonally distorted Heusler structures are computed using density-functional and density-functional perturbation theory within the spin-polarized generalized-gradient approximation. For $0.9<c/a<1.06$, the TA$_2$ tranverse acoustic branch along $[110]$ and symmetry-related directions displays a dynamical instability at a wavevector that depends on $c/a$. Through examination of the Fermi-surface nesting and electron-phonon coupling, this is identified as a Kohn anomaly. In the parent cubic phase the computed tetragonal shear elastic constant, C$^\prime$=(C$_{11}-$C$_{12}$)/2, is close to zero, indicating a marginal elastic instability towards a uniform tetragonal distortion. We conclude that the cubic Heusler structure is unstable against a family of energy-lowering distortions produced by the coupling between a uniform tetragonal distortion and the corresponding $[110]$ modulation. The computed relation between the $c/a$ ratio and the modulation wavevector is in excellent agreement with structural data on the premartensitic ($c/a$ = 1) and martensitic ($c/a$ = 0.94) phases of Ni$_2$MnGa.Comment: submitted to Phys. Rev.