Wednesday, 29 June 2011

bat detecting

Our evening walks have taken on a new dimension. We have always enjoyed the pleasure of walking and have, this year added a refreshed and purposeful interest in wildflowers to our birdwatching. These days I do not leave our house without recycled plastic bags for the collection of seeds or cuttings. Last night I took cuttings of a particularly fragrant red honeysuckle that was growing by the railway and tram lines.

But ... flowers and birds... what is the third dimension?

The answer is bats. I bought myself a bat detector last week and have begun to learn to recognise bats by their distinctive flight & size - and importantly their echo location signals.

These are, of course, beyond our feeble hearing, but a bat detector brings their distinctive calls down to a frequency we can listen to and enjoy.

So far, we have identified our common pippistrelle in a number of locations but have also become aware of their close relation the soprano pippistrelle. Seemingly identical in flight pattern and size, it is only with a bat detector that the common (45kHz) can be separated from the soprano (55kHz). Their chattering calls are very distinctive.

The third bat we have located is either a Leisler's or a noctule. Its call is strongest at 30 kHz and it differs from the pippistrelle by being larger and more round, having more pointed wings and flying in twos and threes in circling swoops around tree tops and above water at a height of three metres.

Our nocturnal wildlife, especially bats and night flying insects are easily overlooked, with the consequence that few of us (myself included) do anything to encourage bats by proving food or roosting or breeding places.

Having got myself a bat detector, my priority is to learn how to use it! But you will see from the photograph that my trusty notebook has been in action and that this under-recorded group of animals is already featuring in my field notes.

We will pursue the ways in which we can promote the interests of bats in future posts.

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