33 research outputs found
Long-term effects of chronic light pollution on seasonal functions of European blackbirds (turdus merula)
No full textLight pollution is known to affect important biological functions of wild animals, including daily and annual cycles. However, knowledge about long-term effects of chronic exposure to artificial light at night is still very limited. Here we present data on reproductive physiology, molt and locomotor activity during two-year cycles of European blackbirds (Turdus merula) exposed to either dark nights or 0.3 lux at night. As expected, control birds kept under dark nights exhibited two regular testicular and testosterone cycles during the two-year experiment. Control urban birds developed testes faster than their control rural conspecifics. Conversely, while in the first year blackbirds exposed to light at night showed a normal but earlier gonadal cycle compared to control birds, during the second year the reproductive system did not develop at all: both testicular size and testosterone concentration were at baseline levels in all birds. In addition, molt sequence in light-treated birds was more irregular than in control birds in both years. Analysis of locomotor activity showed that birds were still synchronized to the underlying light-dark cycle. We suggest that the lack of reproductive activity and irregular molt progression were possibly the results of i) birds being stuck in a photorefractory state and/or ii) chronic stress. Our data show that chronic low intensities of light at night can dramatically affect the reproductive system. Future studies are needed in order to investigate if and how urban animals avoid such negative impact and to elucidate the physiological mechanisms behind these profound long-term effects of artificial light at night. Finally we call for collaboration between scientists and policy makers to limit the impact of light pollution on animals and ecosystems
Data from: Artificial light at night advances avian reproductive physiology
No full textArtificial light at night is a rapidly increasing phenomenon and it is presumed to have global implications. Light at night has been associated with health problems in humans as a consequence of altered biological rhythms. Effects on wild animals have been less investigated, but light at night has often been assumed to affect seasonal cycles of urban dwellers. Using light loggers attached to free-living European blackbirds (Turdus merula), we first measured light intensity at night which forest and city birds are subjected to in the wild. Then we used these measurements to test for the effect of light at night on timing of reproductive physiology. Captive city and forest blackbirds were exposed to either dark nights or very low light intensities at night (0.3 lux). Birds exposed to light at night developed their reproductive system up to one month earlier, and also moulted earlier, than birds kept under dark nights. Furthermore, city birds responded differently than forest individuals to the light at night treatment, suggesting that urbanization can alter the physiological phenotype of songbirds. Our results emphasize the impact of human-induced lighting on the ecology of millions of animals living in cities and call for an understanding of the fitness consequences of light pollution
Dynamic body acceleration increases by 20% during flight ontogeny of greylag geese Anser anser
No full textDespite our knowledge of the biophysical and behavioural changes during flight ontogeny in juvenile birds, little is known about the changes in the mechanical aspects of energy expenditure during early flight development, particularly in migratory species. Here, we investigate in a unique experimental setup how energy expended during flights changes over time beginning with early ontogeny. We calculate overall dynamic body acceleration (ODBA) as a proxy for energy expenditure in a group of hand raised greylag geese Anser anser trained to fly behind a microlight aircraft. We propose two potential hypotheses; energy expenditure either increases with increasing physiological suitability (the 'physical development hypothesis'), or decreases as a result of behavioural improvements mitigating flight costs (the 'behavioural development hypothesis'). There was a significant temporal increase of flight duration and ODBA over time, supporting the 'physical development hypothesis'. This suggests that early on in flight ontogeny behavioural development leading to flight efficiency plays a weaker role in shaping ODBA changes than the increased physical ability to expend energy in flight. We discuss these findings and the implications of flight development on the life history of migratory species
Artificial light at night advances avian reproductive physiology
No full textArtificial light at night is a rapidly increasing phenomenon and it is presumed to have global implications. Light at night has been associated with health problems in humans as a consequence of altered biological rhythms. Effects on wild animals have been less investigated, but light at night has often been assumed to affect seasonal cycles of urban dwellers. Using light loggers attached to free-living European blackbirds (Turdus merula), we first measured light intensity at night which forest and city birds are subjected to in the wild. Then we used these measurements to test for the effect of light at night on timing of reproductive physiology. Captive city and forest blackbirds were exposed to either dark nights or very low light intensities at night (0.3 lux). Birds exposed to light at night developed their reproductive system up to one month earlier, and also moulted earlier, than birds kept under dark nights. Furthermore, city birds responded differently than forest individuals to the light at night treatment, suggesting that urbanization can alter the physiological phenotype of songbirds. Our results emphasize the impact of human-induced lighting on the ecology of millions of animals living in cities and call for an understanding of the fitness consequences of light pollution
thresholds
No full textDataset used for the interpolation of sigmoidal curves to gonadal growth data, in order to calculate dates of threshold passin
body mass and fat score
No full textDataset used for the analysis of variation in body mass and fat score during the experimen
Effect of light at night on molt pattern.
No full text<p>We scored the molt condition (0 = no molt, 5 = completed molt) for the ten primary and the first six secondary flight feathers. In the first experimental year (A), molt was measured between April and December (x-axis). Control birds (blue) experienced dark nights, while experimental birds (red) were exposed to constant light of 0.3 lux at night. Triangles and dashed lines depict urban birds, circles and solid lines depict rural birds. Each symbol represents the sum of molt scores for all feathers of each individual, averaged over all individuals of one group. Error bars represent SEM. Six experimental birds, three rural and three urban, did not finish to molt. In the second experimental year (B), we checked molt only once, on August 13<sup>th</sup>. Vertical bars represent the molt score for each feather, averaged over all individuals of one group. Blue bars (left) depict control birds, red bars (right) depict experimental birds. Within each treatment group, blank bars represent urban birds, filled bars represent rural birds. Error bars represent SEM. For details of experimental set-up see Methods and Figure 1.</p
Effect of light at night on period of rhythmicity and entrainment to light/dark cycles.
No full text<p>A) We measured the length in hours of the main periodicity of locomotor activity between November 1<sup>st</sup> and December 27<sup>th</sup>, 2011, hence before the second experimental year, using a Lomb-Scargle periodogram. Average period length was 1437 min and no significant difference was found between either treatment groups (control = blue/left, experimental = red/right) or populations (rural = filled, urban = blank). Box plots represent, from bottom to top: one standard deviation (s.d.) below the mean, lower quartile, median, upper quartile and one s.d. above the mean. B) Onset and end of daily locomotor activity time measured during the same time period of data shown in panel A. We only show data for treatment groups as this facilitates visualization and interpretation of results. Lines and shaded areas (blue = control, red = experimental) represent mean ± SEM. Dashed black lines represent onset of morning twilight and end of evening twilight. For details of experimental set-up see Methods and Figure 1.</p
