Herbicides and the decline of the partridge: an international perspective.
Partridge (Perdix perdix) diet, population ecology and the abundance of its foods were monitored on a 62km2 ha area of farmland to the west of Brighton, Sussex from 1969 to 1984. Chick mortality rates were measured each year and found to be determined by the availability of their preferred insect food in cereal crops.
By removing host plants for insects, herbicides reduced the amount of insect food for chicks, increased chick mortality rates and in turn reduced the size of the partridge population.
In the world range there were each autumn about 120 million partridges prior to the use of herbicides, this number has now declined by an estimated 75%. In Britain the most important cause of the reduced partridge numbers has been the use of herbicides and this could be the case in other countries.