Light pollution alters the phenology of dawn and dusk singing in common European songbirds

Artificial night lighting is expanding globally, but its ecological consequences remain little understood. Animals often use changes in day length as a cue to time seasonal behaviour. Artificial night lighting may influence the perception of day length, and may thus affect both circadian and circannual rhythms. Over a 3.5 month period, from winter to breeding, we recorded daily singing activity of six common songbird species in 12 woodland sites, half of which were affected by street lighting. We previously reported on analyses suggesting that artificial night lighting affects the daily timing of singing in five species. The main aim of this study was to investigate whether the presence of artificial night lighting is also associated with the seasonal occurrence of dawn and dusk singing. We found that in four species dawn and dusk singing developed earlier in the year at sites exposed to light pollution. We also examined the effects of weather conditions and found that rain and low temperatures negatively affected the occurrence of dawn and dusk singing. Our results support the hypothesis that artificial night lighting alters natural seasonal rhythms, independently of other effects of urbanization. The fitness consequences of the observed changes in seasonal timing of behaviour remain unknown.     

Latitudinal gradients in sea ice and primary production determine Arctic seabird colony size in Greenland

Sea ice loss will indirectly alter energy transfer through the pelagic food web and ultimately impact apex predators. We quantified spring-time trends in sea ice recession around each of 46 thick-billed murre (Uria lomvia) colonies in west Greenland across 20 degrees of latitude and investigated the magnitude and timing of the associated spring-time primary production. A geographical information system was used to extract satellite-based observations of sea ice concentration from the Nimbus-7 scanning multichannel microwave radiometer (SMMR, 1979-1987) and the Defence Meteorological Satellite Programs Special Sensor Microwave/Imager (SSMI, 1987-2004), and satellite-based observations of chlorophyll a from the moderate resolution imaging spectroradiometer (MODIS: EOS-Terra satellite) in weekly intervals in circular buffers around each colony site (150 km in radius). Rapid recession of high Arctic seasonal ice cover created a temporally predictable primary production bloom and associated trophic cascade in water gradually exposed to solar radiation. This pattern was largely absent from lower latitudes where little to no sea ice resulted in a temporally variable primary production bloom driven by nutrient cycling and upwelling uncoupled to ice. The relationship between the rate and variability of sea ice recession and colony size of thick-billed murres shows that periodical confinement of the trophic cascade at high latitudes determines the carrying capacity for Arctic seabirds during the breeding period.     

The fruit fly Drosophila melanogaster favors dim light and times its activity peaks to early dawn and late dusk

The light preferences of fruit flies were tested by 2 different means. First, flies were allowed to choose between different illuminations, and their favorite resting, grooming, and feeding places were determined with an infrared-sensitive camera. Second, the activity levels of the animals during their main daily activity period were determined photoelectrically (via infrared light beams) under different light intensities. Both methods revealed that the flies prefer dim light. They rested, groomed, and fed preferentially in places with a light intensity between 5 and 10 lux, and they showed the highest activity level when the light intensity during the day was kept at 10 lux. Furthermore, when dawn and dusk were simulated by logarithmically increasing/decreasing the light intensity during a 1.5-h interval, the flies' activity maxima occurred at about 7.5 lux during early dawn and late dusk. The results suggest that fruit flies time their clocks by early dawn and late dusk and avoid bright light during the day.     

Seasonal trend in movement directions at dawn and dusk: a study on crow and white herons

Crows (Corvus splendens) and white herons (Ardea alba) inhabit the agricultural landscapes nearby human habitats which represent dynamic ecosystem and show seasonal crop patterns. We studied the movement pattern in these birds at dawn and dusk, during solstices (December and June) and equinoxes (March and September). The movement directions were changed from uniform at dawn to a concentrated distribution at dusk all along the season suggesting that morning movements are more exploratory than evening with seasonal differences. Differential use of directions in December than June could be the effect of temperature, food availability or wind direction and speed. During breeding, less number of directions used suggests that birds might be moving towards the directions having high probability of food availability. It is likely that avian dispersal in space and time is dependent on the food availability however, further studies are required to be carried out.     

Tree size and herbivory determine below-canopy grass quality and species composition in savannahs

Large single-standing trees are rapidly declining in savannahs, ecosystems supporting a high diversity of large herbivorous mammals. Savannah trees are important as they support both a unique flora and fauna. The herbaceous layer in particular responds to the structural and functional properties of a tree. As shrubland expands stem thickening occurs and large trees are replaced by smaller trees. Here we examine whether small trees are as effective in providing advantages for grasses growing beneath their crowns as large trees are. The role of herbivory in this positive tree-grass interaction is also investigated. We assessed soil and grass nutrient content, structural properties, and herbaceous species composition beneath trees of three size classes and under two grazing regimes in a South African savannah. We found that grass leaf content (N and P) beneath the crowns of particularly large (ca. 3.5 m) and very large trees (ca. 9 m) was as much as 40% greater than the same grass species not growing under a tree canopy, whereas nutrient contents of grasses did not differ beneath small trees (<2.3 m). Moderate herbivory enhanced these effects slightly. Grass species composition differed beneath and beyond the tree canopy but not between tree size classes. As large trees significantly improve the grass nutrient quality for grazers in contrast to smaller trees, the decline of the former should be halted. The presence of trees further increases grass species diversity and patchiness by favouring shade-tolerant species. Both grazing wildlife and livestock will benefit from the presence of large trees because of their structural and functional importance for savannahs.     

Long-term influence of simulated territorial intrusions on dawn and dusk singing in the Winter Wren: spring versus autumn

Males of many songbird species have peaks of singing activity at dawn and dusk. Singing during those twilight periods can function in territory proclamation, and males are suggested to adjust song output to the level of intruder pressure. We used song playback during the breeding season to simulate intrusions into territories of male Winter Wrens (Troglodytes troglodytes) shortly after dawn. We then compared male singing behaviour during the dawn and dusk chorus before and 1 day after the simulated intrusion. One day after the playback, male Wrens increased their song output before sunrise, which confirms our results from a previous study on dawn singing in autumn territories. At dusk, on the evening following the playback, males slightly increased song output after sunset, but singing activity at dusk was generally very low. We found no significant changes of song output after sunrise, before sunset, and between 2 days of control without playback. These results are consistent with the hypothesis that dawn and dusk singing is important for territory defence in spring. Unlike in autumn, however, increased singing in spring at dawn and dusk could also serve to defend other resources such as fertile mates or to strengthen the pair bond after a territorial challenge. In comparison with the results on autumnal singing, male Wrens started singing earlier at dawn during the breeding season, and they generally sang more songs at dawn and immediately after playback. The increase in absolute numbers of songs sung in the morning after playback seemed greater in spring than in autumn; however, the proportional increase relative to overall song output was similar in both seasons.     

Natural entrainment without dawn and dusk: the case of the European ground squirrel (Spermophilus citellus).

Observational data collected in the field and in enclosures show that diurnal, burrow-dwelling European ground squirrels (Spermophilus citellus) never were above ground during twilight at dawn or at dusk. The animals emerged on average 4.02 h (SD = 0.45) after civil twilight at dawn and retreated in their burrows on average 2.87 h (SD = 0.47) before civil twilight at dusk. Daily patterns of light perceived by these burrowing mammals were measured with light-sensitive radio collar transmitters in an enclosure (the Netherlands) and in the field (Hungary). The observational data are corroborated by the telemetry data, which show clear daily patterns of timing of light perception including light perceived from the burrow entrances. The first light was observed by the animals on average 3.54 h (enclosure, SD = 0.45) and 3.60 h (field, SD = 0.31) after civil twilight at dawn, whereas the final observed light was on average 3.04 h (enclosure, SD = 0.64) and 2.02 h (field, SD = 0.72) before civil twilight at dusk. Thus, the animals do not perceive the rapid natural light-dark (LD) transitions that occur at civil twilight. Instead, they generate their own pattern of exposure to light within the natural LD cycle. The classical phase response model for entrainment by light or dark pulses cannot explain how the circadian system of this species remains entrained to the external, natural LD cycle while the major LD transitions are created by its own behavior.     

Use of infrared microspectroscopy to determine leaf biochemical composition of cassava in response to Bacillus subtilis CaSUT007

The objective of this study was to investigate the growth stimulating properties of Bacillus subtilis CaSUT007 applied to cassava plants using fourier transform infrared (FTIR) microspectroscopy to monitor the production of cellular components involved in plant growth and development. Cassava stakes treated with CaSUT007 or sterile distilled water were germinated in soil. After incubation for 2 months, CaSUT007 treated plants had higher growth rate and greater biomass than the control. FTIR analysis revealed that the leaves of cassava plants treated with CaSUT007 display FTIR spectra changes in the epidermis and mesophyll tissue. These changes associated with proteins, lipids, and pectins, which are related to changes in plant cell growth and development. FTIR microspectroscopy can be used as a new tool to examine the biochemical changes within the plant tissue. This technique allows us to reveal structural chemical makeup and features of different tissue types.     

Eye size in birds and the timing of song at dawn

Why do different species of birds start their dawn choruses at different times? We test the hypothesis that the times at which different species start singing at dawn are related to their visual capability at low light intensities. Birds with large eyes can achieve greater pupil diameters and hence, all other things being equal, greater visual sensitivity and resolution than birds with small eyes. We estimated the maximum pupil diameter of passerine birds by measuring the diameter of the exposed eye surface, and measured the times of the first songs at dawn of songbirds present in different bird communities, and the light intensities at these times. Using phylogenetic comparative analyses, we found that songbirds with large eyes started to sing at lower light intensities (and therefore earlier) than species with smaller eyes. These relationships were stronger when differences in body size were controlled for statistically, and were consistent between two phylogenies and when species were treated as independent data points. Our results therefore provide robust support for the hypothesis that visual capability at low light levels influences the times at which birds start to sing at dawn.     

Choice of colony size in birds

Most populations of colonial birds exhibit extensive variation in colony size. Field studies over the last decade have shown that individual birds breeding in colonies of certain sizes are apparently more successful than those settling in colonies of other sizes, yet size variation persists. Enough information is now available to suggest four explanations for how birds choose colonies and why colonies vary in size.     

The history of the Eurasian Beaver Castor fiber in Scotland

In 1995 Scottish Natural Heritage proposed a feasibility study to examine the case for reintroducing the Eurasian Beaver Castor fiber to Scotland. Following IUCN guidelines, an important first step is to demonstrate that the Beaver was once a native of Scotland and that the causes of its extinction no longer pose any threat to reintroduced animals. Therefore, palaeontological, archaeological and historical evidence for the former existence of the Beaver in Scotland and the causes of its extinction are reviewed.
Palaeontological and archaeological evidence suggest that the Eurasian Beaver was once widely distributed throughout mainland Scotland. Historical evidence suggests that although it was once probably fairly common, it became extinct between the twelfth and sixteenth centuries, most probably towards the latter. The main cause of its decline and extinction was probably hunting for its pelt, meat and castoreum, but habitat destruction may have been important in the loss of some small isolated populations.
Given that the causes of extinction of the Beaver in Scotland now no longer exist or can be effectively controlled, there is no reason why a feasibility study cannot proceed to assess the practicalities of a reintroduction.     

Use of NADH fluorescence to determine mitochondrial function in vivo

Normal mitochondrial function is a critical factor in maintaining cellular homeostasis in various organs of the body. Due to the involvement of mitochondrial dysfunction in many pathological states, the real-time in vivo monitoring of the mitochondrial metabolic state is crucially important. This type of monitoring in animal models as well as in patients provides real-time data that can help interpret experimental results or optimize patient treatment. In this paper we are summarizing the following items: (1) presenting the solid scientific ground underlying nicotine amide adenine dinucleotide (NADH) NADH fluorescence measurements based on published materials. (2) Presenting NADH fluorescence monitoring and its physiological significance. (3) Providing the reader with basic information on the methodologies of the fluorometers reflectometers. (4) Clarifying various factors affecting the monitored signals, including artifacts. (5) Presenting the potential use of monitoring mitochondrial function in vivo for the evaluation of drug development. The large numbers of publications by different groups testify to the valuable information gathered in various experimental conditions. The monitoring of NADH levels in the tissue provides the most important information on the metabolic state of the mitochondria in terms of energy production and intracellular oxygen levels. Although NADH signals are not calibrated in absolute units, their trend monitoring is important for the interpretation of physiological or pathological situations. To better understand the tissue function, the multiparametric approach has been developed where NADH serves as the key parameter to be monitored.