Where Are The Serotines?

Part of my bat-watching zone.  13 May 2011.

Unlike my last bat post, this one has a photograph. Are there any bats in it? There are not.

Serotine bats have been seen in the neighbourhood of Hayes. They like to roost in old buildings, but no-one has found where these come from. Last night, a dozen people surrounded a large building in Hayes.

It seemed a likely candidate. They had been seen in the woods nearby, as well as other woods a mile or so away. Other likely buildings have already been checked out, with no results.

Organised by Ishpi Blatchley, a local bat expert, we started to assemble half an hour before sunset. Ishpi split us up to surround the building, and we watched, and listened on our detectors. I was covering the aspect of the building in the photograph. We saw no serotines. One of us saw a pipistrelle, which we weren't looking for.

Planes flew past a gibbous moon. Bats didn't. We waited until well after sunset, when any bats would definitely have flown out to eat. Our target building was eliminated as a serotine roost.

Serotines are twice as big as the common pipistrelles. My route back home took me through the wood behind the building. I heard pipistrelles as I walked along, and suddenly I saw two serotines flying and feeding along the edge of the trees. They were echolocating at 27 kiloherz, a loud popping call like a giant pipistrelle on my heterodyning detector. Another of the group joined me and we watched them cruising back and forth, snapping up insects, sometimes swooping just above our heads.

Where are they coming from? We could see houses nearby. Less likely, but that will be the next investigation.