Tuesday, 11 July 2017

Tales from a dawn bat emergence survey

I was going to say that on balance I prefer dawn bat surveys to dusk, but actually there's no "on balance" about it, I definately prefer dawn bat surveys. Yeah it's not great dragging yourself out of bed at 1:30am and making your way to a site you may never have been to before to try to locate a tree while you're still half asleep in the pitch black that you know exists only from a point on a map and then having to find a particular feature of the tree which has been "scoped in" as a potential bat roost by a surveyor who had the luxury of daylight. But all that said, I still prefer dawn surveys to dusk surveys. Even the drive to the survey can be good, with foxes at the side of the road and occasionally cubs.

I sit in front of the tree (occasionally a building) with a bat detector and the survey begins two hours before sunrise, so at this time of year I have to be in position at 3am. I say sit, all experienced and sensible bat emergence surveyors take a chair, it's the only way to  do it. Those who don't are insane, simple as that. Basically I'm watching for bats returning to a roost site, in the case of a building that might be a hole in a wall or under the eaves, or into the apex, but in a tree it could be a crack or fissure in the bark, or occasionally a woodpecker hole.

The first hour is usually pretty dull, with very little activity of any kind. I might hear the occasional bark or grunt from some wild animal, or perhaps the hoot of a tawny owl, but usually there is not even much bat activity. As the dawn approaches the temperatures drop, this morning from 17'C at 3am to 15'C at 4am. It may not seem much of a drop, but you do notice it and this is the time that you wish you'd brought another layer.

Around this time things start happening. Badgers can sometimes be seen. Last week a badger walked within 2m of where I sat, oblivious to my presence. This morning a fellow surveyor had two badgers scuffling within 1m of her. Today I had to be content with a badger crossing the field about 10m away from me. Of course in this half light and at 10m away it's mainly just a shape in the dark, but it was a full moon this morning so the field was well lit and I could see the badgers black and white striped face. I thought that it was going to keep walking right past me, but it stopped for a moment, sniffed the air and was suddenly aware of me and ran back across the field and disappeared. Shortly after the badger had departed, two more shapes appeared, but they were moving much too fast and erratically for badger and when they got closer I could see that they were brown hares, chasing each other around the field. Meanwhile, somewhere in the distance a Roe deer starts barking, or perhaps a fox, and the dawn chorus starts from nowhere. First one bird starts singing nervously and feebly, then suddenly within a few minutes, almost as if nobody wanted to be the first to break the silence, the air is full of bird song and calls. "Pink, pink, pink", a blackbird alarm call alerts me to an unseen danger in the field, but whatever it is it's hidden by the hedge. Then I can see it, incerdibly a tawny owl lands on a gate, less than 3m in front of me. By this time it's almost daylight and I can see the bird well. It sits there for a minute and then disappears into the wood. All is calm again.

Meanwhile the bat detectors have gone crazy. Brown long-eared, common and soprano pipistrelle and noctule, all flying around the orchard this morning. I rarely see bats emerge or return into trees, probably because its often very dark under the tree, but buildings are a different matter, and last week in almost complete daylight at sunrise I watched a common pipistrelle fly around the building, land on the wall little more than 3m from where I was sitting and look at me for a second before scurrying under the eaves and into its daytime roost. How tiny bats look when they land.

Around this time a barn owl might drift by with its ghostly flight, and in the distance a little owl calls, and often there's something unexpected. Two weeks ago as I was packing up at the end of a survey I noticed a purple hairstreak butterfly roosting in a barley field. That must rank as the most unexpected sighting I have ever had on bat survey.

And of course the great thing about all of this, the icing on the cake as it were, is that virtually none of this can be captured on a camera (hairstreak excepted!). So I don't waste time trying to take a photo of the badgers and bats, I just sit there in silence and observe, and that way it sinks deeper into the memory banks and becomes the experience of a lifetime, to be remembered forever, long after the digital images have been lost, detroyed or forgotten. Then it's back to the hotel to try to snatch an hour or twos sleep before the next survey. What will it be today?

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