City birds that experience light at night are ready to breed
earlier than their rural cousins
Street lamps, traffic lights and lighting from homes are
causing a rise in our night-time light levels. For some time now, scientists
have suspected that artificial light in our towns and cities at night could
affect plants, animals and us, humans, too. Studies, however, that have tested
this influence directly are few. Scientists from the Max Planck Institute for
Ornithology in Radolfzell, Germany, recently investigated how light conditions
in urban areas at night affect European blackbirds (Turdus merula). They found
that animals exposed to low night-time light intensities, comparable to those
found in cities, develop their reproductive system earlier: their testosterone
levels rise and their testes mature earlier in the year. They also begin to
sing and to moult earlier. The ever-present light pollution in cities may
therefore exert a major influence on the seasonal rhythm of urban animals.