| Home | << 1 >> |
|
Dominoni, D., Quetting, M., & Partecke, J. (2013). Artificial light at night advances avian reproductive physiology. Proc Biol Sci, 280(1756), 20123017.
Abstract: Artificial 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.
|
|
Dominoni, D. M., Helm, B., Lehmann, M., Dowse, H. B., & Partecke, J. (2013). Clocks for the city: circadian differences between forest and city songbirds. Proc Biol Sci, 280(1763), 20130593.
Abstract: To keep pace with progressing urbanization organisms must cope with extensive habitat change. Anthropogenic light and noise have modified differences between day and night, and may thereby interfere with circadian clocks. Urbanized species, such as birds, are known to advance their activity to early morning and night hours. We hypothesized that such modified activity patterns are reflected by properties of the endogenous circadian clock. Using automatic radio-telemetry, we tested this idea by comparing activity patterns of free-living forest and city European blackbirds (Turdus merula). We then recaptured the same individuals and recorded their activity under constant conditions. City birds started their activity earlier and had faster but less robust circadian oscillation of locomotor activity than forest conspecifics. Circadian period length predicted start of activity in the field, and this relationship was mainly explained by fast-paced and early-rising city birds. Although based on only two populations, our findings point to links between city life, chronotype and circadian phenotype in songbirds, and potentially in other organisms that colonize urban habitats, and highlight that urban environments can significantly modify biologically important rhythms in wild organisms.
|
|
Matzke, E. B. (1936). The Effect of Street Lights in Delaying Leaf-Fall in Certain Trees. Amer. J. of Botany, 23(6), 446–452.
Abstract: Street lights in the City of New York cause a retention of the leaves of certain trees: Carolina poplar (Populus canadensis), London plane (Platanus acerifolia), sycamore (Platanus occidentalis), and crack willow (Salix fragilis). Illuminated portions of a tree retain their leaves; shaded portions of the same tree do not. One side of a tree, or the lower part, may thus have numerous leaves, while the other side, and the upper part, may be entirely devoid of foliage. A relatively weak light, at a distance of as much as 45 feet from the tip of the nearest branch, may cause retention of numerous leaves. Light intensity as low as 1 foot candle, or less, may be effective. Some leaves may be retained at least a month, others more than that, beyond the normal season. The orientation of the light with respect to the tree – i.e., north, east, south, and west – is not significant. In Populus canadensis all of the leaves ultimately fall, abscission apparently taking place at the base of the petiole. In Platanus acerifolia and Platanus occidentalis some of the leaves are retained until killed by low temperature; then some of them break off above the base of the petiole. Leaves of the Populus and Platanus species discussed remain green unusually long when receiving additional illumination. Leaves of these same trees do not emerge from the buds earlier in the spring as a result of the additional illumination.
|