STUDIES ON THE CEREAL ECOSYSTEM
177
partridge chicks to account for the chick predation. (In 1970, for
example, 28 P . perdix chicks per km2 were estimated to have been taken
by predators in area (a)). However, crows were not especially numerous
in the centre of area (a) and they spent most of their time on the
surrounding grassland.
3. Rat
This species is sometimes a predator of nestling birds (Elton, 1942)
but presumably not of nidifugous species unless these are found in a
confined space. More rats are usually killed on game preserves than all
the other possible predators combined. The actual numbers are uncertain since most of the poisoned ones die out of sight and underground. Rats are mainly vegetarian and even in summer most are found
near buildings rather than in the more open fields favoured by partridges.
We have no evidence for the views of some writers (Maxwell, 1911;
Vesey-Fitzgerald, 1945) that rats are significant wild game chick
predators. They are responsible for far fewer egg losses than the fox
(Middleton, 1967) and under most circumstances would be unlikely to
tackle healthy adults or well grown chicks. Rats were scarce in area (a).
4. Mustelidae
The two remaining common predators are the stoat (Mustela erminea)
and weasel (Mustela nivalis), and they deserve detailed consideration.
They are very difficult to control on game preserves and they are serious
pests of small game on the rearing field. Their numbers fluctuate
considerably and although their feeding ecology on farmland has been
much neglected, they are well adapted to feeding on partridge chicks,
and we have records of both species feeding on healthy chicks. Both
species were common in area (a) (see Table XVIII).
Stomach analysis of weasels following the methods of Day (1966)
showed that they preferred the vole (Microtus agrestis L.). Other
small mammals, especially the nocturnal Apodemus spp. , were not taken
in proportion to their relative abundance in the fields, as indicated by
their frequency in Longworth traps (unpublished). Birds were important
in summer and these included some partridge chicks even in area B.
It has been assumed that the violent fluctuations in the numbers of
weasels caught by gamekeepers from year to year (Middleton, 1934)
reflected the abundance of Microtus, and there is some evidence of
this (Southern, 1964; Jefferies and Pendlebury, 1968; cf. Nicrotus as
reported to Snow, 1968). This aspect is currently being investigated
by us, having regard for the fact that the efficiency of trapping these
predators is also related to their food supply.
I n the year 1968-1969 it has been calculated (King, 1971) that the
177
partridge chicks to account for the chick predation. (In 1970, for
example, 28 P . perdix chicks per km2 were estimated to have been taken
by predators in area (a)). However, crows were not especially numerous
in the centre of area (a) and they spent most of their time on the
surrounding grassland.
3. Rat
This species is sometimes a predator of nestling birds (Elton, 1942)
but presumably not of nidifugous species unless these are found in a
confined space. More rats are usually killed on game preserves than all
the other possible predators combined. The actual numbers are uncertain since most of the poisoned ones die out of sight and underground. Rats are mainly vegetarian and even in summer most are found
near buildings rather than in the more open fields favoured by partridges.
We have no evidence for the views of some writers (Maxwell, 1911;
Vesey-Fitzgerald, 1945) that rats are significant wild game chick
predators. They are responsible for far fewer egg losses than the fox
(Middleton, 1967) and under most circumstances would be unlikely to
tackle healthy adults or well grown chicks. Rats were scarce in area (a).
4. Mustelidae
The two remaining common predators are the stoat (Mustela erminea)
and weasel (Mustela nivalis), and they deserve detailed consideration.
They are very difficult to control on game preserves and they are serious
pests of small game on the rearing field. Their numbers fluctuate
considerably and although their feeding ecology on farmland has been
much neglected, they are well adapted to feeding on partridge chicks,
and we have records of both species feeding on healthy chicks. Both
species were common in area (a) (see Table XVIII).
Stomach analysis of weasels following the methods of Day (1966)
showed that they preferred the vole (Microtus agrestis L.). Other
small mammals, especially the nocturnal Apodemus spp. , were not taken
in proportion to their relative abundance in the fields, as indicated by
their frequency in Longworth traps (unpublished). Birds were important
in summer and these included some partridge chicks even in area B.
It has been assumed that the violent fluctuations in the numbers of
weasels caught by gamekeepers from year to year (Middleton, 1934)
reflected the abundance of Microtus, and there is some evidence of
this (Southern, 1964; Jefferies and Pendlebury, 1968; cf. Nicrotus as
reported to Snow, 1968). This aspect is currently being investigated
by us, having regard for the fact that the efficiency of trapping these
predators is also related to their food supply.
I n the year 1968-1969 it has been calculated (King, 1971) that the