Bat emergence & autumn swarming

Pipistrelles, noctule, Daubenton's, horseshoe and Natterer's bats. Nationwide, United Kingdom.

Best time: 1 Jul – 30 Sep (July to September). Where: Woodchester Mansion, Gloucestershire, Wicken Fen, Cambridgeshire, Greywell Tunnel, Basingstoke Canal, Hampshire (United Kingdom). Time of day: Emergence 20–40 min after sunset (pipistrelles first, then Daubenton's over water), feeding through the first 2 h of dark.

• You can go on your own
• Free
• No binoculars needed
• Sound 3/5

Open it in the interactive calendarSunrise and sunset listening times for the day you pick, and the map.

When is the best time?

Peak: 1 Jul – 30 Sep. July–Sept (emergence); Aug–Oct (autumn swarming at caves and tunnels)

Active from 15 Apr to 31 Oct (April to October) in a typical year.

Time of day

Emergence 20–40 min after sunset (pipistrelles first, then Daubenton's over water), feeding through the first 2 h of dark; autumn swarming at tunnel mouths peaks between midnight and 03:00.

• Emergence: 20 min after sunset → 2 h after last light
• Autumn swarming: 00:00 → 03:00

What will you hear?

Mostly ultrasonic: echolocation and feeding buzzes, social calls. Noctule social calls and some horseshoe calls are partly audible.

Binoculars?

No binoculars needed. Dark; a bat detector matters far more than binoculars. No lights on tunnel mouths.

Where to go

• Woodchester Mansion, Gloucestershire — Greater and lesser horseshoe roost in the unfinished mansion; bat evenings run by the trust. Map
• Wicken Fen, Cambridgeshire — Daubenton's trawling the lodes at dusk; almost any calm river or canal works. Map
• Greywell Tunnel, Basingstoke Canal, Hampshire — One of Britain's largest bat hibernacula; autumn swarming at the tunnel mouth. Watch from the towpath only. Map

How to go on your own, and what it costs

Greywell Tunnel: the Basingstoke Canal towpath is a public path — stand on it at the tunnel mouth after dark, no lights on the entrance. Wicken Fen: the lode banks are public paths, free at all hours. Woodchester Mansion: bat evenings and admission are paid (Fri–Sun in season). Local Bat Conservation Trust groups run free or cheap bat walks nationwide.

Cost: Free on towpaths and public paths; Woodchester Mansion £15 admission (2026), bat evenings extra (check).

Who runs access

• Woodchester Mansion – bat experiences (NGO) — Horseshoe bat evenings in summer.
• Bat Conservation Trust – local bat group walks (NGO) — Detector walks run by volunteer groups across the UK.

Field-recording notes

Full-spectrum ultrasonic recorder (384 kHz+) essential. All bats and roosts are protected — no entering roosts or tunnels without a licence, and no lights on the tunnel mouth during swarming. Bat Conservation Trust local groups run walks nationwide.

Sources

• Bat Conservation Trust

Similar spectacles

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• Autumn bat swarming at the Segeberg Kalkberg caveGermany · Bats · peak 20 Aug–25 SepAudible chatter and wing-flutter of hundreds of Myotis circling the cave mouth; on a full-spectrum detector, dense FM sweeps and social calls — one of the busiest bat soundscapes in northern Europe.
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More: all spectacles in the United Kingdom · bats · the United Kingdom in July · the United Kingdom in August · the United Kingdom in September