One may interpret seasonal changes through a number of avenues: temperature fluctuations, hours of sunlight, precipitation and other weather events. Behaviour of living things contribute to the experience of spring. As budding new shoots make their appearance through the soil or on bare branches, those higher on the food web may sense that the time of plenty is drawing near. 'Dormant creatures twitch'; some may come to the conclusion that it is a good time to breed. Thus, for many species, the reproduction cycle begins.