On the theme of birds, new research has shown that songbirds that live in city areas sing shorter and faster songs than birds that live in rural areas. City birds even adjust the pitch of their songs to be heard over the noise of the city. Ecologists at the Leiden University in the Netherlands analyzed bird songs in rural and urban areas in Europe. They found that the same species of bird will sing songs shorter, faster and higher in pitch in the city than birds of the same species in the forest. Researches hypothesized that the reason for this is that cities are full of low-frequency noises and that by shifting their songs to higher frequencies they make their songs stand out. This research may explain why some species of birds are better adapted for life in a city than others. Here is the link.