The ecology and conservation of the grey partridge Perdix perdix.
The recent growing concern for the loss of wildlife on agricultural land in Britain has often focused on the Grey Partridge Perdix perdix, once a common bird of arable and mixed farmland over much of the country, now declining alarmingly. Its economic importance as a quarry species has meant that there are reliable long-term records of Partridge numbers and has provided financial incentives for its study, giving rise to over 50 years of ecological work on the species.
The Grey Partridge originates from the temperate steppe grassland ecosystems of Eurasia, but the successive advance of agriculture must have assisted its spread into the new habitats provided so that it is now a native of much of Europe and Central Russia and has been successfully introduced into North America. It is strictly monogamous, requiring permanent grassy cover for nesting, often on a raised area to avoid flooding, where it lays an average clutch of about 16 eggs. Despite its cryptic plumage and unobtrusive behaviour at the nest site, Partridges suffer from high levels of nest predation.
In Britain, the chicks hatch in mid- to late June and are looked after by both parents, feeding initially on insects, followed by a transition to weed seeds and vegetation after about two weeks. The juveniles remain with their parents in family coveys until late winter when pairs are formed. Spring dispersal of pairs takes place over short distances and the species is very sedentary.
Dramatic declines in densities of Grey Partridges have been experienced throughout their range (fig. l). The most extensive long-term study of this decline has been the Game Conservancy's Partridge Survival Project on 62 km2 of arable and sheep farmland on chalk downland in Sussex, England. Here, decreases of up to 80% have been recorded in the last 20 years. In other areas of Britain and Europe, the species is faced with local extinction (Potts 1986).
The causes of this catastrophic decline have been the subject of extensive research, some of which will be summarised here. The problems of loss of nesting habitat, increased predation due to a reduction in predator control and the ecological effects of pesticides will be considered in turn.