The ecology and adaptability of the pheasant (Phasianus colchicus) and grey partridge (Perdix perdix) in relation to changing land-use in Britain.
Intensification of agriculture has keen the single most important factor in land-use change in Britain over the past forty years. Large fields containing monoculture cereals provide less by way of habitat to wildlife than smaller fields under a more diverse cropping system, and this problem has more recently been exacerbated by the widespread prolific use of pesticides, which have generally removed seasonal food insects and plants of pheasants and grey partridges (Potts 1984). Indeed, the decline since the 1950's in the numbers of grey partridges harvested has been partially the result of a decline in the survival of chicks, attributed to reductions in their insect food supply obtained cereal fields (Potts 1978). Pheasant chicks also rely on insects during their early lives (Hill in press) and so agricultural practices may well have detrimentally affected wild pheasant populations, although this remains difficult to determine because of widespread annual restocking for shooting purposes.
Perhaps the second most important change in land-use has been the exponential increase in afforestation during the past century (Peterken 1981). This has occurred at the cost of a loss of semi-natural primary woodland. For instance, the area of woodland coppiced in rotation, which probably represents ideal winter pheasant habitat in Britain, has declined dramatically.
There are limits to the adaptability of any species faced with a changing environment, particularly when changes occur over very short periods of time. In this paper we present data from intensive studies of the two species, and use the results to show how the situation and the populations of each might be improved with generally moderate charges in management practices, whether from farming or silviculture. Previous prescriptions have been subjective because of a lack of information on the habitat requirements of the species and their responses to change.
Pheasants were probably introduced to the British Isles by the Normans during the 11th century, and used primarily for food. It was not until the late 18th century however, that pheasant shooting became an important sport, and by this time most of the 'wildwood' which covered Britain until the neolithic period, existed only as small pockets, Most of the English countryside had been transformed to its present overall appearance by the 12th century as a result of clearance of woodland for agriculture (Rackham 1976). As a result, pheasants only began to spread throughout Britain, within a much reduced woodland environment.
In contrast to the pheasant, the grey partridge is a monogamous native of the British Isles (the only indigenous lowland Galliform) which lives almost exclusively on open farmland. Prior to forest clearance, the species was probably fairly scarce being confined to moorland edges, coastal sand dune and forest clearing habitats. During the late 18th and early 19th century, however, there was approximately a four-fold Increase in numbers which has been attributed firstly to an increase in food supplies arising from the introduction of rotational farming in 1790 and secondly to an increase in nesting cover due to the partitioning of open fields that followed the General Enclosure Act of 1845. By the 1880's partridge numbers reached their maximum, not only in Britain (Potts 1980), but throughout Europe (Cramp & Simmons 1979). One hundred years later numbers had plummeted by 50-90 per cent in Britain and the species was in rapid decline all over its previous range. Clearly while thegrey partridge was well suited to early landscape changes in Britain, it has not been able to adapt to more recent intensification of farmland.
Commercial forestry began, albeit on a small scale, during the early 18th century, but total area of woodland in Britain, largely as a result of afforestation, has increased exponentially from 1890 to the present day (Fig. l). Over the same period there has been a dramatic decline in traditionally coppiced woodland, as demand for thatching spars and 'faggots' for fuel declined (Fig. 1).
This paper investigates adaptability by pheasants and grey partridges against this historical background changing land use.