52
The Essex Naturalist
vagrant in Britain on about 10 occasions, (including from North Sea oil
installations). The two most recent records involve Essex.
On 22nd October 1994, a bat was collected from a block of flats at Chadwell
Heath that was later identified as a female parti-coloured bat. It weighed 19g
and was released the following day. The second occurrence is of a male found in
the Roman River Valley on 5th June 1996 (J. Greenwood pers. comm.). In an
emaciated condition (7.5g), probably due to a torn wing membrane, this bat
died later the same day.
Serotine Eptesicus serotinus (Schreber 1774)
A large bat that is apparently declining in Essex as evidenced by fewer sightings,
an absence of new roost records and rare reports of injured bats found by the
public. Laver never saw a Serotine and he wrote of the first two Essex records
from Pattiswick Hall, Coggeshall, around 1860 and Broomfield in 1894.
In Essex, serotines form summer roosts in houses and churches, the largest
being of 45 bats found at South Woodham Ferrers in 1988. Despite searching,
this colony has not been recorded since 1992 when 17 bats were present. At
another roost in Vange, numbers have declined from 25 to 12 since 1994. This
decline is probably due to habitat loss, particularly the loss of pasture (Robinson,
1994). In early summer, serotines feed predominantly on chafers (Amphimallon
spp. and Melolontha spp.) and in autumn on dung beetles (Aphodius spp. and
Geotrupes stercorarius) (Robinson, 1993). The recent introduction of avermectins
as worming agents has seen a decline in dung beetles and therefore a reduction in
the preferred food of serotines. In 1988, a large individual (forearm 56.8mm)
showing flavistic coloration of the fur was found dying at North Fambridge.