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We study the developing temperature profile in planar laser-ablation in the limit of a completely ionized low-Z plasma. The problem is analyzed both analytically and numerically, assuming complete laser absorption by near-critical absorption and inverse bremsstrahlung absorption, and heat conduction by flux-limited diffusion. We show through dimensional analysis that the temperature in the resulting corona and conduction zones is characterized by scaling relations expressed through three dimensional parameters and depends on two dimensionless parameters. Our results form a phase diagram for the behaviors of the maximal temperature as a function of time at different phases of the flow. The phase boundaries curve describes the transition times as a function of the flux limiter. We show that for low values of the flux-limiter the flow behavior is highly dependent on local details of the laser absorption at the critical surface. Measured experimentally, the identified transition times between the different phases can be used to infer the characteristic value of the flux-limiter. [ABSTRACT FROM AUTHOR]

Different weather conditions are known to affect bird migration, yet the influence of fog and low clouds on migrating birds has been rarely examined so far, and hence, their impact on bird movement is not well understood. Fog avoidance could be a consequence of visual limitations within the fog or may be the outcome of deteriorated soaring conditions due to the obstruction of the sun. We carried out a radar study at the Strait of Messina, which is a bottleneck for migrating birds traversing the Central Mediterranean Sea, to determine if the intensity of diurnal soaring bird migration was influenced by fog and other weather variables. We recorded bird movements using an X-band radar, which can detect birds flying within the fog, and recorded weather conditions using local meteorological observations. We examined if bird passage rate (number of tracks/hour) at the radar site was influenced by fog, wind speed and direction, air temperature and the time of day. Our findings suggest that fog was the most important factor affecting bird migration intensity as recorded by the radar, indicating that birds actively avoided flying into fog. In addition, wind direction affected bird migration intensity, with lower numbers recorded with southerly tailwinds and higher numbers recorded with westerly crosswinds. Our findings highlight a consequence of widespread meteorological conditions, and of fog in particular, on migrating birds, with implications for bird migration navigation, path length and flight energetics. [ABSTRACT FROM AUTHOR]

Global warming alters various avian phenological processes, including advanced reproduction and migration schedules. In birds, individual appearance is largely determined by plumage, influencing, for example, bird attractiveness, social status and camouflage. Juveniles of most passerine species replace their nest-grown plumage during the first months of life, a process that is called post-juvenile feather moult. Using data from ten natural history collections, we show that the extent of the post-juvenile moult has increased significantly over the last 212 years (1805–2016), a trend that is positively correlated with the temperature of the environment. Therefore, it seems that birds replaced more feathers under warmer conditions, causing juveniles to appear more similar to adult birds. Moreover, in several species, we describe a male–female switch in the extent of moult, with females currently replacing more feathers than males compared to the past. These results demonstrate different biological responses to climate warming by different phenotypes. Most passerine bird species replace part of their plumage within the first year of life. Here, using data from 4,012 individuals of 19 species, Kiat et al. find that the extent of post-juvenile moult has increased over the past 212 years and this correlated with the global temperature increase in this period. [ABSTRACT FROM AUTHOR]