A
dovecote can be of any building materials and of any plan shape.
The windows (if any) were small, unglazed apertures high in the walls,
protected
against birds of prey
by
wooden lattices or wire grills.
A
lattice at Empingham,
Rutland
Remnants of a decayed wire
grill at Letheringham, Suffolk
.......
A
small doorway
at Kirkden, Angus
Until
the eighteenth century the doorway was always small, less than 1.5
metres high, so that the pigeon-keeper could block it with his stooping
body as he entered.

From
that time it became common to make doorways of conventional
height to suit the classical proportions in which contemporary
buildings were designed.
...........................................
................................ This
doorway at Kelston, Somerset,
.................................is
only 3½ feet
(1.06m)high.
The pigeons entered at a turret on the roof called a louver.

The
louver at Eardisland,
Herefordshire, before
restoration. The inclined
boards six
inches apart were
designed to keep out the larger
birds of
prey.
The louver at Kelston, Somerset,
after restoration.
The
inside was lined with nesting places for the birds - now called
nest-holes if they were incorporated in the solid walls, or nest-boxes
if they
were constructed separately.

...........Stone nest-holes at Murroes, Angus

............................................................................................Brick
nest-boxes at Bayfield, Norfolk
.........Wooden nest-boxes at Elmdon, Essex
A former dovecote can usually be recognized as a relatively tall building
(in relation to its plan area) with few apertures. In practice most dovecotes
have been adapted for secondary uses since they passed out of use for
their original purpose, and now often have enlarged doorways and extra
windows inserted later.
The louver was the most difficult feature to maintain, so this was often
removed when it was no longer needed; tiles or slates were laid over
the aperture where it had been. Very few original louvers have survived.
There
is documentary evidence that dovecotes were built in England from
the middle of the twelfth century, but the earliest ones which survive
date from the fourteenth century. 
Built
in 1326 at Garway, Herefordshire,
this is the oldest firmly dated dovecote in England
They continued in full economic use until 1793, when the French Revolutionary
Wars began. (It has been claimed that they passed out of use when the
use of turnips to feed livestock increased the total supply of meat,
but this is not true; there were more dovecotes in the eighteenth century
than ever before).
One effect of the French wars was to change the economics of British
agriculture, so that it became more profitable to sell corn than to feed
it to pigeons. Many dovecotes were demolished. Others were modified to
house fewer pigeons - for instance, by inserting a floor at mid-height,
retaining the upper part as a pigeon-loft while adapting the lower part
of the building to another use.
Economic and legal changes caused pigeon-keeping for meat to go out
of favour, earlier in some areas than others.
By the middle of the nineteenth century the practice was virtually forgotten
in Britain, although dovecotes continued in use abroad.
The first historians to take an interest in these neglected buildings
at the end of the nineteenth century had very little firm information,
and proposed various fallacious theories which have persisted almost
to the present day.
Since 1988 an increasing body of historical research has rediscovered
how dovecotes were used.