To hell with birdies, I want BATS!

Spring has sprung, the grass is riz,
I wonder where the birdies is?
Cancel that - I don’t care,
But when will bats take to the air?

I’ve hugged the fire and shivered lots,
I’ve had enough - I want some hot.

And when it comes, what I want most

Is wakeful bats - not one, a host!

All this tweeting is quite nice,

But I’ll ignore it in a trice.

It’s chips and chops I really like,

Hollow claps, clicks and suchlike.

My detectors polished til it gleams,

Batteries are charged, ready it seems.

‘Tis patience I am really short of,

I need some bats, to adore and love.

So, don’t keep me waiting, little bat,

‘Tis time to make your belly fat.

I’ll wait no more, I can’t, I vow,

So shift your butt and fly right now. 

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The harbingers of spring, heralding bat surveys

In spring each year I, like most bat-workers champ at the bit, waiting for the survey season to kick off in May. I can't resist looking at some of my favourite roosts, to see if any bats have arrived yet.  A couple of weeks ago I spent a fruitless evening watching the roof of our cottage, to see if any of our resident Common Pipistrelles had showed up yet - they hadn't. 

Last week Charlotte Meyer-Wilson and I visited one of our favourite Soprano Pipistrelle maternity roosts to see what was happening. In summer around 1,000 bats occupy this roost, but we were happy to see 13, especially as we were playing with an infra-red video camera, which allowed us to see into the roost entrance and watch the bats moving around and interacting, prior to emerging.

It's at this time of year that I watch out for what I think of as the 'harbingers of spring' - three common hedgerow plants that flower early and stand out, each one showing that the bat season is a little closer.

The first to appear is Coltsfoot (Tussilago farfara), its cheerful yellow flowers poking through the flattened mat of last year's dead vegetation. Its chunky, scaley stem is almost a reminder that it's tough and flowers before anything else round here.

After Coltsfoot, the next harbinger of spring is the Lesser Celandine (Ficaria verna), with shining petals and glossy cordate leaves. It's slightly scruffy flowers alwyas make me wonder if they were built on a Friday afternoon.

My third botanical harbinger of spring is Garlic Mustard (Alliaria petiolata). Following on from the other two, the speed at which their tall stems zoom up in every hedgerow is amazing, allowing them to flower and set seed before they’re overwhelmed by the mass of species that follow. 

When garlic mustard shows I know that within 1-2 weeks the hedgerows will, for a brief period, be awash with swaying white Garlic mustard flowers. And that means it's time for the bat survey season to start, which puts an even bigger smile on my face!

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An early spring...maybe?

Last night I took a group of ecology undergraduates to a 200 year-old kirk (that's church to those without a Scottish education) in East Lothian, to watch for bats. I had my fingers firmly crossed on the way there: although I know the church and churchyard to have plenty of summer bat activity it is still very early in the season for bats to be at all dependable.

In the summer the kirk has a Soprano Pipistrelle (Pipistrellus pygmaeus) maternity roost within the roof structure and also has Brown Long-eared Bats (Plecotus auritus) inside the kirk itself - during the summer there is usually a light scattering of droppings over the pews. Last year I watched one flying up and down inside the kirk, warming up before going out to forage.

The most I could really hope for was that there might be one or two individual Pipistrelles foraging around the kirkyard - it's in a secluded, tree-lined valley, alongside a burn (or stream if you prefer), so it's good foraging habitat, even this early in the season.


When we arrived and walked round there were no droppings inside the kirk, althought there were some on the exterior, making me hope that at least a few of the Pipistrelles may be present.

At sunset a few Soprano Pips overflew the kirk at first, commuting from other locations in the valley. Then there came an excited squawk over the radio, announcing that someone had seen a bat emerge from the edge of the kirk roof and we watched about 30 Sopranos emerge from the same spot where I watched several times that number come out in the autumn last year.



I am sure that there will be many more than 30 bats in that roost in mid summer, when Soprano Pipistrelle females gather in large numbers to rear their young - these are probably the first arrivals. Interestingly, we also heard a male Soprano in songflight, the string of mating calls designed to attract mates. This is primarily an autumn activity, but seems to occur a little in spring as well.

It's not hard to see why the bats are active so early in April. The chart below shows night-time temperatures at the Met Office's Gogarbank station, near Edinburgh. There have been two weeks of fairly consistent temperatures around 7 to 8 degrees, which seems to be the level at which bat activity in this area picks up. As a happy coincidence, last night was also the warmest night of the year so far.



However, this might not be the end of the story. It's still very early in the year and weather is never as reliable as we would like. As you can see below, last year April started off warm like this and then went into a cold period for a couple of weeks, causing bat activity to fall away until nearly the end of the month. Only time will tell what will happen this year.



My website: plecotus.co.uk
Contact me: mailto:blog@plecotus.co.uk

Is spring springing yet?

When does Spring start? According to the Met Office, spring starts on 1 March, although the traditional start is the vernal equinox, on the night of 21/22 March. Here we are in mid April, so surely spring has started?

From a wildlife point of view, spring activity starts when the prevailing weather conditions permit, so in truth it's quite a variable thing, not just in terms of date, but geographically. The south of England is likely to experience signs of spring one or two weeks before they appear here in Scotland.

With some members of Lothians Bat Group, I went to Edinburgh's Blackford Pond after sunset, one evening last week. If you live in Edinburgh this is a great place to see large numbers of Daubenton's Bats (Myotis daubentonii) and Soprano Pipistrelles (Pipistrellus pygmaeus) in the summer, and the group usually run a bat walk there every year. On this occasion we wanted to see if there were the first signs of bats emerging from hibernation yet.

With an ambient temperature after sunset of just 2.5 degrees celsius, it was questionable whether we'd see any bats at all, but what was probably a lone Soprano Pipistrelle passed by a couple of times and we watched one, and later two Daubenton's Bats feeding on the pond. There was very little food for them, so they were having to range over the whole of this large pond, to find enough flying insects to eat (they looked to be small Sedge Flies). With such a low temperature, it's possible that these few bats were some of last year's juveniles, desperate for food after the long months of hibernation.

So is it spring? Well, not really from a bat point of view, as it seems like the main population are still in hibernation. The graph below shows the night-time temperatures at the Gogarmor meteorological station, to the west of Edinburgh, since the start of April. As you can see, there was a brief peak of warmer temperatures at the start of the month, but it has been quite cold at night since then.

Having said that, there are other signs of spring. As we walked around Blackford Pond, we had to tread carefully to avoid a large number of toads, commuting towards the pond, in order to mate?

Since then I have also seen some discarded eggshell from what must be a very optimistic bird and last weekend, I watched a group of Brown Hares (Lepus europaeus), boxing and chasing each other: the so-called "mad march hare" behaviour, associated with the onset of the breeding season. This behaviour actually continues through to September, but is far more noticeable just now, whilst the grass is short.

Hopefully we'll get a spell of warmer weather soon, and we'll start to see more bat activity, as the adults move out of their hibernation sites and the move towards maternity roosts commences, ready for the breeding season around June. My bat detectors are charged up and ready...

My website: plecotus.co.uk