fragments of insects, they crumble easily to a find powder, whereas
mouse and rat droppings are pasty when fresh and become increasingly
hard as they dry. Care must be taken not to underestimate the numbers
of bats using a barn as the quantity of droppings visible does not
necessarily provide a guide to the numbers of bats using the roost.
Very few droppings could be seen in the barn with 35 Natterer's bats.
Brown Long-eared bats are more commonly found in barns than
Natterer's. These bats tend to be found using the central ridge beam
and hence the place to look for bat droppings would be on the floor
beneath the ridge. If the barn is in use, droppings should be visible
scattered on top of stored items such as chemical drums or vehicles,
even if the barn is regularly swept.
It was found that 82% of suitable barns had evidence of bats; this
represented 40 barns. Fifteen of these barns had evidence of
Natterer's bats (37.5%), 13 had evidence of Brown Long-eared, just 4
had Pipistrelles and only 2 had Serotines. Some of the barns were used
by more than one species of bat. Twenty-one were only occasionally
used and 6 had had bats in the past but not recently. Evaluation of the
data revealed that the Natterer's roosts all had common features. The
barns were all listed buildings, all had hollow mortise joints, open/absent
doors, unimpeded flying space within the barn and were all close to
woodland. The figures for Hertfordshire revealed that 83% of barns
used by bats were listed buildings. Of these listed buildings, 50% had
evidence of Natterer's bat and 25% had breeding roosts of this species.
Since 1991, six breeding Natterer's sites have been found in
Hertfordshire. One is in a roof space of a converted stable, five are in
barns. Of these five, only one colony roosts at the apex of a barn roof,
whilst the other four all use mortise joints. Unfortunately, it has
become common practice to convert these redundant barns into luxury
homes. One of the breeding roosts has already been lost and planning
applications are currently being considered for the conversion of
another. Barn conversions are therefore a major conservation problem.
If important sites are not identified, bat roosts will be lost.
In areas where these types of barns are a common feature. Bat Groups
could play a significant role in ensuring that bats like our Natterer's bats
continue to remain a part of our countryside.
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