The Essex Naturalist
53
Noctule Nyctalus noctula (Schreber, 1774)
A large bat that emerges before dusk and can be identified by bat detector.
Described as common by Laver, it is still widespread in Essex although rarely
seen in large numbers. In the early 1980s up to 200 were counted emerging from
a tree near Colchester (A. Wake pers. comm.) and in 1989 up to 50 were seen
over Hanningfield Reservoir. More recently smaller groups have been observed
feeding over the London reservoirs, Ardleigh and Abberton Reservoirs,
Connaught Water, Danbury Lakes, Tilbury town and Mersea.
Summer roosts are in trees and have been found at Danbury, Thundersley and
Wickham Bishops where breeding was proved.
Leisler's bat Nyctalus leisleri (Kuhl, 1818)
Unknown to Laver, this bat is more commonly found in Essex than most other
counties. It has been recorded in 17 of the 10km squares and summer roosts
have been found at Aveley, Coggeshall, Little Hallingbury, Danbury and
Bicknacre. A mobile species, roosts are occupied for short periods, particularly
during June and July, and at least three houses on one Coggeshall estate are used
sequentially.
A migratory species on the Continent, its winter status in Britain is unknown.
The only winter records are of one found in Grays in November 1993 and
another in Colchester in February 1994.