CORN BUNTING
The
British population of Corn Buntings appears to be highly sedentary, and
restricted to lowland arable farmland.
The
sexes are identical, with grey brown upper parts, streaked blackish, and whitish
buff underparts. They are thick set,
with a heavy head and shortish tail, and have a squat appearance. They are
slightly larger than House Sparrows. The
males’ song, a harsh trill like jangling keys, is distinctive, and is usually
given from a wire, fence post, or other prominent position.
Breeding
territories are usually established in April, and the first clutch, usually of
4-6 eggs, is laid in April or May. Incubation
takes 12-14 days, and young leave the nest before they can fly, usually 9-12
days after hatching. Some pairs
raise two broods.
The
distribution map from “An Atlas of the Breeding Birds of Shropshire” (1992),
shown on the previous page, shows that Corn Bunting are almost wholly restricted
to low-lying land in the north-east quadrant of the County.
All known breeding sites here are on arable farmland, and the species
particularly associates with barley. Due
to crop rotation, some breeding sites will change location each year, and some
tetrads at the edge of the range were not occupied in every year, so the 1992
map probably overstates the position in any one year.
The population was estimated at 3-7 pairs per occupied tetrad, giving a
County population of between 400 and 900 pairs at that time.
Nationally,
Corn Buntings declined very steeply between the mid-1970s and mid-1980s, showing
an estimated 88% decline between 1970 and 1999.
They disappeared altogether from large parts of their range, and the
species was added to the Red List of
the Population Status of Birds in the
The
more recent Distribution Map on the previous page reflects the decline locally,
although the species is almost certainly under-recorded. As it is largely
sedentary, locations where it is seen outside the breeding season are almost
certainly close to breeding sites. Most records from other times of the year
have corresponding breeding season records, but a few do not. Such records are
shown on the 2000 – 04 Map as
green dots.
In
2004, the Shropshire Ornithological Society carried out a survey of
approximately 20% of tetrads that were found to be occupied 1985-90 during
fieldwork for The Atlas (1992).
Twenty-two tetrads were surveyed. Corn
Bunting were only found in eight (36.4%) of them.
Map C on the previous page shows all the tetrads that were surveyed in
2004. The red dots are the tetrads
where Corn Bunting were found, and the open circles are tetrads where Corn
Bunting were found in 1985-1990, but not in 2004.
It therefore appears that the catastrophic decline which has affected
this species nationally has also occurred in
Corn
Buntings form flocks in winter, and feed on farmland seeds, particularly in
stubble fields. The population decline is attributed mainly to a big reduction
in this winter food supply, caused by agricultural intensification over the last
20–30 years, particularly the change from spring to autumn cereals, resulting
in the loss of winter stubbles, coupled with use of herbicides to remove
“weeds”, another major source of seeds. These changes have reduced the
over-winter survival rate of adult and young birds. Insufficient young birds are
reaching breeding age, to replace the older breeding birds that would die
naturally, but which are dying at an even faster rate because of starvation.
Corn
Buntings feed their young in the nest on insect larvae, particularly
caterpillars, so their breeding success will also be impaired by the use of
insecticides. Many chicks starve to death in the nest. Earlier harvesting of
crops also reduces the possibility of a second brood being raised, which reduces
still further the number of young birds that fledge each year.
Habitat
changes necessary to reverse the population decline of this species therefore
include increasing the supply of insect larvae in the summer, and, more
importantly, increasing the supply of seeds throughout the year, particularly in
winter. Reduced use of herbicides, and increased plant diversity in conservation
strips and headlands at the edge of fields, is necessary to help this species.