The Norsey Wood Society works closely with Basildon Borough Council, the owners of Norsey Wood Nature Reserve, an ancient woodland which is also
a Site of Special Scientific Interest on the edge of Billericay in Essex, UK
Bats-more-info
Bats of Norsey Wood - more information
A Typical Year in the Life of a Bat
Bats need to hibernate during the winter period and that is generally from October to April. In warm periods between, they may awake and venture out to feed and drink. Bats easily become dehydrated. To assist them through the hibernation period they have the ability to go torpid. That is to lower the heart rate and body temperature to conserve energy.
Bats will mate in the autumn but delay the pregnancy until the early spring of the following year; gestation taking from 6 to 8 weeks. To be actively pregnant whilst in hibernation over the winter would be fatal. The males form a lek (a meeting place for coupling) in the autumn by singing a love-song and the females queue for mating. It’s short on romance in the bat world!
Maternity Roost
Then in early spring, when the females leave their winter roosts they collectively gather in a maternity roost; usually in the roof of a manmade structure. With Common Pipistrelles it can number anywhere up to 100 females but for the Soprano Pipistrelle it can number in excess of 1000 females. The roof of the Hanningfield Reservoir EWT Visitor Centre is a case in point for the latter with a record count of c.1300 in 2017!
New Life
In early July the young start to be born. They usually have a single ‘pup’ but twins are not unknown. As dusk falls the mothers leave their ‘pup’ in a crèche within the roost to fly off into the night to forage; thus enabling them to produce milk to suckle their young. Occasionally, the mother will take her ‘pup’ with her, clinging to her chest! The young take about three weeks to reach maturity before they are ready to fly. Watching a maternity roost one can sometimes spot the first flight of a youngster. Several of the mothers will fly close to the maternity roost calling excitedly as if encouraging their pups to brave the outside world! Its first flight looks nervously unsteady but it quickly acquires the skills to stay airborne! It will then accompany its mother into the woodland for several weeks and both will return to the maternity roost where suckling will continue. Meanwhile, the mother will teach her offspring the potential feeding areas in the landscape and the many roosting crevices in the various trees along with roosting opportunities offered by manmade dwellings.
Feeding
Different bat species prefer a particular habitat to find food according to its preference for insect prey. The smaller bats mainly feed on midges and gnats, and it is said that they need to catch and eat up to 3000 a night! Bats will identify where there is insect activity in different weather conditions; typically along the rides and along the edges of the woodland coppiced areas. Some will also hawk between the gaps of the upper storey canopy. On some nights, when the moon is bright, one can see them against the sky between the silhouetted tree canopies. Synchronous hatching swarms of gnats and midges rising in the warm air will be heavily predated! The larger species of bat will fly high and directly across country but the smaller species will follow hedge, tree lines and other landscape features by way of navigating from roost to their favoured feeding areas; sometimes several kilometres away. “Connectivity” across the countryside is one of the important projects that the ‘Essex Wildlife Trust’ promotes with its ‘Living Landscapes’ remit.
Bats scoop their aerial prey with their tail and transfer it to their mouth. It is carried out so quickly that it is only visible when filmed and viewed in slow motion! Noctules and Serotines, the larger bat species, eat cockchafers and the larger moth species. Noctules will fly high across woodlands and countryside whilst the Serotine hunts along the sides of tree and hedge belts. If feeding conditions are right that night they can hunt for a couple of hours and, if fully replete, return to their roost and snooze and preen the rest of the night away! The Noctule and Serotine will roost in tree holes whilst the latter can also be found roosting in manmade structures.
Echolocation
A subject covered well in technical publications but basically it is a form of radar / sonar that has evolved for this group of night flying mammals. Contrary to popular opinion, bats have quite good eyesight but it is not efficient enough to navigate by night. By emitting a rapid series of clicks made from the vocal chords they are then reflected back and interpreted as a mental picture as to what lays ahead of them. A moth or midge can then be targeted and homed in on. The strange structure (to our eyes!) of their faces and ears are designed to emit and receive this information. The faculty of echolocation is so quick and efficient that a bat flying through the branches and leaves of a tree in the pitch black of night can successfully avoid collision! The call is of such a high frequency that a bat detector has been designed to convert the call to a lower frequency so as to be heard by the human ear. Each bat species has its own signature call when feeding in its preferred habitat but most bats sound similar when flying through trees! The echolocation call of a Noctule Bat, whilst in its feeding habitat, sounds like the sky is falling in when listened to via a heterodyne bat detector!
Identification
There is an excellent foldout bat identification chart published by the ‘Field Studies Council’ (FSC). And a booklet ‘Bats’ by Phil Richardson published by the ‘British Natural History Series’. Bat identification comes down to detective work; building up the various clues of the echolocation calls, habitat type and flight behaviour. Even advanced electronic bat detectors can often give results open to question or just inconclusive. Sometimes the only reliable way to identify the range of bats in an area is by trapping; an endeavor that requires much training and a licence issued by ‘Natural England’.
Norsey Wood is closely in touch with the ‘Essex Bat Group’ who advises on the various aspects with respect to bats. The Countryside Services Ranger annually holds bat events where the basic skills of bat detecting are demonstrated in the field. To build up further knowledge on the subject, getting involved with the various courses held by the EBG is the way forward.