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Barford Features

This month, make good use of the (hopefully) warm evenings by observing Bats in Warwickshire


Of the 16 species of bat found in the British Isles, 12 have been recorded in Warwickshire. Flying bats are easy to find if you look in the right sort of places, at the right time of year, and in reasonable weather conditions. But before considering these aspects, the importance of safety must be emphasised.

Safety considerations

If you are planning to study bats, whether on your own or with others, there are a number of safety issues to be considered. Some of these apply to any fieldwork, but others are particularly relevant to working after dark.

Here are some basic tips:

1. Decide where you are going to work and if possible carry out reconnaissance in daylight as well as after dark.

2. Look for hazards - e.g. water, rusting metal, barbed wire, holes in the ground.

3. Let someone know where you are going, when, and for how long. A mobile phone is useful and adds to your personal safety.

4. Wear good footwear. Walking boots are ideal, because you are less likely to turn an ankle in an unseen rut.

5. Even during warm summer evenings you can get cold and miserable standing around after dark, so make sure you are wearing several layers.

6. If you plan to be out for some time, take some food and a warm drink, especially if you are going to be working during your normal sleeping hours. Walking around at night uses a lot more energy than being in bed or watching television!

7. Make sure that you have plenty of torches, spare bulbs, and batteries. Head torches have the advantage of leaving your hands free should you need to negotiate some obstacle.

When can you detect bats

Bats in Britain hibernate, because there are too few aerial insects available for them to feed on during the winter months. Exactly when they start to hibernate and when they become fully active again depends upon the weather. On average, hibernation lasts from the end of October to the middle of March. Most bats will have brief periods of activity interrupting hibernation, but the winter months are not a reliable time to find bats on the wing.

In June and July the females give birth and this is a good time to study bats. The nights are short and warm and insects are abundant. Females are particularly busy feeding to supply their single foetus with nutrients and then to produce milk for suckling the newborn pup. Females come together to form maternity roosts and these can number several hundred individuals, so roosts are most likely to be located at this time. Roosts may be in tree holes, buildings, bridges or other structures. Bats and their roosts are legally protected in Britain and many other countries and it is not normally legal to enter a roost or disturb roosting bats, but there is no problem standing outside the roost with a detector.

Bats feed mostly around dusk and dawn when the majority of night-flying insects are active. These are therefore the ideal times to watch bats. The middle of the night usually reveals less bat activity and is darker so they are harder to see. If you can stand operating at dawn, this is when the best views are available as many bats seem reluctant to call it a night and return to their roost, especially when food is abundant.

Bats are most active on warm, humid, windless nights. They will tolerate a little rain, but appear to hate really windy conditions; presumably because it plays havoc with echo-location and flight dynamics. Bats may be less active on moonlit nights because they are more vulnerable to predation by owls, but the light can make it easier to observe them. Even very powerful torches do not appear to disturb bats on the wing, and used in conjunction with a detector, can facilitate good views.

Where can you detect bats

Flying uses up a lot of energy so bats need to catch plenty of insects to stay healthy; a tiny Pipistrelle may eat up to 3,000 insects in one night! So, the best places to look for bats are where insects gather at night - around woodland, hedgerows, rivers, ponds, lakes, gardens, or even white street lights.

The following are often good places for bats and likely to provide the novice bat-watcher with a rewarding experience:

1. Outside roost sites
If you know of a bat roost and the owner is amenable, they why not wait outside to watch the bats emerge? You stand a good chance of seeing plenty of bats and should be able to count them out because they usually leave one at a time, although it may take a large colony an hour or more to leave. There is also the advantage that in mid-summer most species leave before it is properly dark so you may get a good view. Watching bats return to a roost at dawn is even better. They often swarm around outside the roost before entering and it may be virtually daylight before the last bat disappears inside. Bats do not only roost in old buildings and tree holes. The Pipistrelle bat (Pipistrellus pipistrellus or Pipistrellus pygmaeus) is quite happy in modern buildings sometimes moving into newly-built houses before the owners!

2. Over bodies of water
Many species of bat take the opportunity to feed on the abundant insects associated with water. The Daubenton's bat (Myotis daubentonii) feeds almost exclusively over still or gently flowing water and is easy to identify and observe. This bat flies low and at a constant height, its wing tips almost entering the water on the downbeat. Many of its prey are lifted off the surface of the water by its large back feet which are employed like fishing gaffs. It also maintains a regular flight path, making it easy to illuminate. Canals in Britain are especially good places to watch them because they are narrow, fairly straight, and usually have a tow-path. They are also deep and steep sided so safety is paramount.

3. Woodlands
Broadleaf woodlands may be better bat habitats than conifer plantations because they not only support many insects, but generally provide more roost holes. It is best to try detecting in clearings, rides, and woodland edges because they give bats a less cluttered flight path and are easier for humans to walk through. Most British species will hunt in woodlands. If conditions are windy, the middle of a wood or the sheltered side of a wood is a good place to look for bats.

4. Illuminated areas
Bats are often attracted to lights. Research has shown however, that bats only seek out white lights, because these are the ones that attract insects. So look out for bat-watching opportunities where there are tree-lined roads lit with white lights, floodlit buildings, or security lights. Bats are also attracted to moth traps, swooping in to take insects before they enter the trap, much to the consternation of lepidopterists! Of course, the presence of lighting has the added bonus of making it easier to see bats, although this advantage is countered by the fact that your eyes do not become properly accustomed to the ambient darkness.

Information sourced from the "Warwickshire Bat Group".

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