STUDIES ON THE CEREAL ECOSYSTEM
163
The aim of the studies so far described in this paper was to explain
the spatial variations in the densities of those insects which are eaten
by partridge chicks. This section mainly discusses those aspects of the
vertebrate ecology of cereal crops which also have particular relevance
to the survival of partridge chicks.
The downlands were originally occupied by many species of mammal
and reptile, but only the hare (Lepus europaeus Pallas) seems able to
live permanently on regularly cultivated fields. The others are still to
be found on the field boundaries together with their predators. The
most important predatory mammals around open fields are the fox
(Vulpes vulpes L.) and the Mustelidae; their most important prey are
rabbits, voles and mice. The population sizes of these prey species
change more rapidly than those of their predators, partly because the
predators can to some extent switch to alternative prey.
The most dramatic change in the field-edge mammal fauna has been
the crash and temporary absence of the rabbit as a result of the disease
myxomatosis. The status of the harvest mouse (Micromys minutus
Pall.) is a little uncertain but it is generally supposed to have declined
over the past 30 years or so, especially in northern Britain. The ecology
of this species is currently being investigated at North Farm by our
colleague Roger Trout.
The most representative birds of the downland pastures are, in
order of abundance, the skylark (Alauda arvensis L.), meadow pipit
(Anthus pratensis (L.)), grey partridge, lapwing ( Vanellus vanellus (L.))
and wheatear (Oenanthe oenanthe (L.)). The latter has declined, however, since it mainly nests in rabbit burrows. The skylark and lapwing
normally breed on cultivated fields even though their eggs are often
destroyed by rolling. The other species nest in the field boundaries,
where they occur together with scrub and woodland edge species such as
the hedge sparrow (Prunella modularis (L.)) and blackbird (Turdus
merula L.). The corn bunting (Emberiza calandra L.) often nests in
cereals but it generally needs fences or bushes for delivering its song.
The greatest change in the farmland avifauna over the present century
has been the decline of the corncrake (Crez crez (L.)) and grey partridge.
Despite its name the corncrake most frequently nested in meadows and
grassland. Later, however, the broods moved into corn. The date
of grass cutting is important; in June or early July, cutting would
generally destroy the nest or newly hatched brood. Indeed it has been
calculated that 85% of nest losses can be directly attributed to grass
cutting. Earlier cutting and the adoption of machines seem likely to
have been the main cause of the decline (Norris, 1945).
There are two other common gamebirds in the study area, the
redlegged partridge (Alectoris rufa L.) and the pheasant ( P h i a n u s
163
The aim of the studies so far described in this paper was to explain
the spatial variations in the densities of those insects which are eaten
by partridge chicks. This section mainly discusses those aspects of the
vertebrate ecology of cereal crops which also have particular relevance
to the survival of partridge chicks.
The downlands were originally occupied by many species of mammal
and reptile, but only the hare (Lepus europaeus Pallas) seems able to
live permanently on regularly cultivated fields. The others are still to
be found on the field boundaries together with their predators. The
most important predatory mammals around open fields are the fox
(Vulpes vulpes L.) and the Mustelidae; their most important prey are
rabbits, voles and mice. The population sizes of these prey species
change more rapidly than those of their predators, partly because the
predators can to some extent switch to alternative prey.
The most dramatic change in the field-edge mammal fauna has been
the crash and temporary absence of the rabbit as a result of the disease
myxomatosis. The status of the harvest mouse (Micromys minutus
Pall.) is a little uncertain but it is generally supposed to have declined
over the past 30 years or so, especially in northern Britain. The ecology
of this species is currently being investigated at North Farm by our
colleague Roger Trout.
The most representative birds of the downland pastures are, in
order of abundance, the skylark (Alauda arvensis L.), meadow pipit
(Anthus pratensis (L.)), grey partridge, lapwing ( Vanellus vanellus (L.))
and wheatear (Oenanthe oenanthe (L.)). The latter has declined, however, since it mainly nests in rabbit burrows. The skylark and lapwing
normally breed on cultivated fields even though their eggs are often
destroyed by rolling. The other species nest in the field boundaries,
where they occur together with scrub and woodland edge species such as
the hedge sparrow (Prunella modularis (L.)) and blackbird (Turdus
merula L.). The corn bunting (Emberiza calandra L.) often nests in
cereals but it generally needs fences or bushes for delivering its song.
The greatest change in the farmland avifauna over the present century
has been the decline of the corncrake (Crez crez (L.)) and grey partridge.
Despite its name the corncrake most frequently nested in meadows and
grassland. Later, however, the broods moved into corn. The date
of grass cutting is important; in June or early July, cutting would
generally destroy the nest or newly hatched brood. Indeed it has been
calculated that 85% of nest losses can be directly attributed to grass
cutting. Earlier cutting and the adoption of machines seem likely to
have been the main cause of the decline (Norris, 1945).
There are two other common gamebirds in the study area, the
redlegged partridge (Alectoris rufa L.) and the pheasant ( P h i a n u s