Beginner's Guide to British Bat Watching: When, Where and How to Start

The first bat of the evening rarely announces itself. You are standing by a gate at the edge of a field, the light has gone soft and orange, and something small and dark flickers past your shoulder and vanishes. Not a bird. Not a moth. Almost certainly a pipistrelle, hunting insects in near-darkness by echolocation.

Britain has around eighteen species of bat, and watching them is one of the most accessible kinds of wildlife watching here. You do not need to travel to a reserve or get up at dawn, and the best sites are often a short walk from home. What follows is what to look for, when to go, and how to enjoy it without doing any harm.

It helps to know who you are watching

Most British bats are small, fast and brown, and you will not identify all of them on sight. That is fine. Eighteen species have been recorded in Britain, seventeen of them breeding, but a small number account for the great majority of encounters — and they behave quite differently once you know what to look for.

• Common and soprano pipistrelles — tiny, fast, jerky flight around trees, gardens and streetlights. By far the most likely bats in a British garden, and the two are almost identical on the wing.
• Noctule — our largest bat, flying high and straight over treetops, often appearing before sunset.
• Daubenton's bat — hunts low over water in straight lines, sometimes skimming the surface with its tail or feet.
• Brown long-eared bat — slower and fluttering, hovering close to foliage, usually well after dark.
• Rarer residents — serotine, Natterer's, barbastelle and others, plus horseshoe bats in parts of Wales and south-west England, which flutter slowly and hunt in a distinctive "fly-catching" style.

Scale is worth keeping in mind, because it explains a lot of what you are seeing. A common pipistrelle weighs about as much as a twenty-pence piece and has a wingspan of roughly 20 cm, which is why it can change direction in what looks like mid-air stalling. A noctule can be four times heavier, with a wingspan nearer 40 cm, and it flies like something much more purposeful — fast, level and high, often well above the hedge line where the pipistrelles are working.

Echolocation is the other half of the picture. Every British bat calls into the dark and listens for the returning echo, and those calls are pitched far above what we can hear. Each species has a characteristic frequency: the common pipistrelle around 45 kHz, the soprano nearer 55, and the noctule down at 25 kHz or lower, which is close enough to the edge of human hearing that some people can just make out a dry ticking as one passes. You will not hear the rest with your ears. That is what detectors are for.

When to go: seasons and the hour after sunset

Weather matters more than anything else. Bats stay put in heavy rain and strong wind, so pick a mild, still, dry evening after a warm day. Even a clear night turns quiet if the temperature drops sharply, and a warm, muggy evening with the odd cloud is often better than a cold, crisp one. Wind speeds bats down and makes their prey harder to find; once the thermometer falls below about 10°C, activity drops off sharply, because the insects they depend on simply stop flying.

Activity builds through spring and peaks in midsummer. May to September is the reliable window, with July and August usually the busiest. By autumn, bats are feeding hard before hibernation, and some species gather at hibernation sites to swarm and mate. From November to March most bats are hibernating, though you may still see one on a mild winter night.

The golden hour is the one right after sunset. Noctules sometimes appear while the sky is still bright, pipistrelles follow as the light fades, and brown long-eared bats often wait until it is properly dark. There is a second, smaller burst of activity just before dawn, which is worth knowing about if you are an early riser rather than a night owl.

Within the season, timing also depends on what the colony is doing. Females gather in warm roofs and lofts through late spring to raise a single pup each, so June and July are quiet in some places and frantic in others. By August the pups are flying and the count of bats on the wing roughly doubles — which is why an ordinary August evening can feel suddenly busy after a sluggish June.

Where to look

Water is the best starting point, because insects gather over it and bats follow the food. A canal towpath, a river footpath or a park pond gives you somewhere safe to stand and watch, and often several species at once.

• Canal towpaths, rivers and ponds — look for low, straight flights just above the surface, the signature of Daubenton's bat.
• Hedgerows and field margins — bats use these as commuting routes between roosts and feeding areas, often along the same line night after night.
• Woodland edges and rides — pipistrelles work the edges while noctules cross overhead.
• Churchyards and parks with mature trees — old trees and old buildings offer roosting gaps, and the open ground between them makes bats easier to follow.
• Bridges and weirs — the water below and the stonework above can give you two species in one spot.
• Streetlights — moths collect around them and pipistrelles are quick to take advantage of the easy meal, though lighting is a mixed blessing for bats overall.

How to watch: kit, technique and patience

You can start with nothing at all, and many people do. But a little kit transforms the experience, and none of it is expensive.

• A torch with a red filter — red light disturbs bats far less than white, and it is still bright enough to see a bat against a hedge.
• A simple heterodyne bat detector — the cheapest entry point. You tune it to a frequency and listen to a crackle, a click or a wet slap, and you soon learn which sounds belong to which species.
• A note book — time, temperature, wind, first bat, species guessed. Patterns emerge after only a few evenings.

Be wary of relying on a phone app alone. Most phone microphones cut off somewhere around 20 kHz, well below the range of most British bats, so without a hardware detector they hear nothing. A detector plugged into a phone, or a dedicated recording detector, is the honest way in.

Technique matters as much as gear. Arrive twenty minutes before sunset, stand still, and look up at the treeline rather than straight ahead — bats crossing a pale sky are easiest to see, and most of them are above eye level. Use the torch in short bursts rather than sweeping it around, and let your eyes adjust. When a bat is hunting, the detector will produce a run of rapid clicks ending in a fast, harsh burr: the feeding buzz, produced as the bat closes in on an insect. Learning to hear that buzz is the moment bat watching stops being guesswork.

You will hear far more bats than you will ever see clearly. That is not a failure of technique. That is simply what bat watching is.

Rules of the roost: watching without doing harm

All British bats and their roosts are legally protected under the Wildlife and Countryside Act 1981 and the Habitats Regulations. It is an offence to kill, injure or disturb a bat, or to damage or obstruct a roost — and the roost itself is protected even when the bats are not in it, which means a summer gap in a roof is still a roost in January. Nothing about casual watching gets near that line, but a few habits keep it that way.

1. Never enter a roost or a hibernation site, and never shine a torch into a roof space, cave or hollow tree.
2. Do not handle bats. If you find one grounded, keep pets and children back and call the National Bat Helpline on 0345 1300 228.
3. Avoid strong lighting. Slow-flying species such as brown long-eared and horseshoe bats tend to avoid lit areas, so a floodlit commute route can cut a colony off from its food.
4. Keep your distance at dusk, keep dogs on leads near water, and leave before the site empties of bats so you are not following them home.
5. Record what you see. The National Bat Monitoring Programme, local bat groups and iRecord all use public sightings, and a few evenings of notes from a towpath genuinely add to the picture.

Start with a warm, still evening in July, a stretch of water within walking distance, and an hour of your time. Sit on a bench, listen for the ticking, watch the low black shapes stitching the surface, and let the dark do the rest. The bats were there all along. Once you know how to look, you will find them almost anywhere.

Photo: KELLEPICS / Pixabay