Bats at Whetsted Wood

It's 8.35pm on Saturday 7th May, the sun has just set on another lovely warm and sunny day. For the last week everyday has got warmer and it feels like summer. So different from the previous week, when for much of the time it was colder than during the Christmas week.

Maybe it's just my perception, but for the last few years I have noticed that the weather patterns appear to get ‘stuck’ for weeks, if not months, at a time. December 2015 - Late February 2016 was the warmest winter ever recorded in the UK. Then in the last week of February the wind switched to the north and north east and for much of the next two months the weather was cold and spring was delayed. 1st May arrived and all changed, summer arrived almost overnight ! This current warm spell is forecast to continue, but maybe a little cooler and I am enjoying typing this post under a sunshade, drinking a cool beer, looking out across the garden at butterflies and bumble bees visiting the flowers in the garden. Is it climate change, or just part of the Earth's changing weather patterns? Time will tell. 

Anyway back to Saturday night. I am standing on the edge of Whetsted Wood looking south across a grass field, awaiting the arrival of the local bats, as they visit to feed along the woodland edge and the Tudeley Brook. The air is full of tiny midges and gnats, hovering above my head, the ground vegetation and newly unfurled tree leaves. A smorgasbord of aerial insect nibbles, irresistible to any bat making a beeline to this ‘picnic spot’.

Bats often have their ‘favourite’ feeding areas, places they know they can rely on to have a regular supply of food. For many years I have known about this bat ‘picnic spot’ on the edge of Whetsted Wood, used by local bats, as they awake from a daytime spent asleep.

 8.43pm and the first bats arrive, two pip 45’s (common pipistrelle) flying along the Tudeley Brook from a southerly direction. One minute later and both pip 55’s ( soprano pipestrelle) and pip 45’s are in the air above me, feeding on the gnats and midges. They are flying fast, high and covering a large area of the wood and surrounding fields, but don't seem that determined to stay. Maybe this is just a quick ‘snack stop’! More pips, both 45 & 55’s arrive over the next ten minutes. The aerial display is fast and furious. I have the bat detector tuned to 45 KHz, and with my headphones plugged in I can pick up both the 45 & 55 pips clearly. I am all alone in a warm field with a darkening skyline, lost  in my own soundscape of repeating clicks and occasional buzz’s as I watch an old fashioned style aerial dogfight between the bats and midges above me. The buzz sounds are feeding buzz’s, a rasping sound, as the bat speeds up its sonar echo location system, to home in on a midge and as the buzz ends, so does the midge’s life !

 By 9.05pm many of the first arrivals have moved on, flying away in a northerly direction, following the Tudeley Brook towards the River Medway, about 2 kms away. Left behind are two pip 45’s who for the next 20 minutes hoover up as many insects as they can catch.

The best way to see them as the light fades is to lie low and look towards the West, where the light remains for the longest. Silhouetted against the sky, the bats can be picked out. They are flying slower now, in a more determined pattern. This is their feeding area and they know the landscape well. They can pick out every tree, shrub & bush. They hug the edge of the wood and trees along the stream. Flying where the midges are densest, the pair of pip 45’s feeding buzz’s and loud and frequent. Flying between 4 - 8 feet above the ground and at a lower speed, it's helpful that I am sitting on the ground, as I marvel at their aerial skills. My own private air show, however their flying skills are far superior to any human pilot and all the time the soundscape of clicks and buzz’s is ringing in my ears.

 At 9.14pm two robins suddenly start singing from either side of the field. A last minute declaration to each other to keep to their own territory, their own side of the fence so to speak. This verbal spat lasts for about two minutes and then they stop and presumably turn in for the night.

The pair of pip 45’s frantic feeding is drawing to a close now and eventually at 9.30pm they are no longer around. It's dark now and I cannot tell in which direction they headed, but they will be moving on to another favoured food stop, before they have full tummies. Feeding contniues for about two hours after sunset, before bats tend to take a break, to digest their night time meal. Feeding then starts again later, just before dawn and then they return to their daytime roosts to sleep during the day.

I leave now, heading back to civilisation, but as I look back I see a dog walker, torch in hand, patrolling the footpaths around Whetsted Wood. I wonder if this person knows that above them a nightly duel is taking place.

Sunset bat emergence visit

After another fabulously warm and sunny day and a clear evening promised, I thought I would grab the opportunity to pop along to a house near to the rail crossing in Lucks Lane and check out the Soprano Pipistrelle (Pipistrellus pygmaeus) roost in the west facing gable end of the house. This is a roost I ‘discovered’ about 8 years ago on a springtime evening stroll along the lane. Passing beneath the overhanging gable I heard bats chattering just before they emerged from the roost. Since then I have visited the roost in May / June, when time allows.

West facing gable end of the house where the bats roost.

The owner is aware that bats roost in the house during spring and early summer period and takes part in a national bat roost survey, run every June by the Bat Conservation Trust, for this is an important bat maternity roost, where baby soprano pipistrelle bats are born.

Soprano pipistrelle bats were only recognised a separate species in 1990, up to then the two ‘pip’ species in the UK were thought to be just one species. As its easier, I tend to call them ‘Pip 55’s’ for they produce their best sounds at a sound level of 55,000 HTZ, whereas the common pipistrelle bats are best heard at 45,000 HTZ and so are known as ‘PIP 45’s’.

Soprano pipistrelle bat (Wikipedia)

The human ear can hear up to about 20,000 HTZ. So how can you hear bats which are above our hearing range ? You use a bat detector ! This is a ‘magic’ box which reduces the sound by a factor of 10, so that we can hear the sound bats are making when they are flying. All bats in the UK fly mainly at night and feed upon insects. They navigate the night time skies using sonar, in effect shouting and waiting for the echo to return and using their very sensitive ears create a soundscape of their environment. Each of the 17 bat species in the UK makes a separate and recognisable sound and like bird song once you get your ear tuned in you can identify the different bats flying around in the sky,  between dusk and dawn.

A simple bat detector

So back to my spur of the moment emergence visit, what was involved ? All bats species in the UK are legally protected, so surveying must take place in a manner which causes them no harm. Actually it’s really pretty simple. I just drove round to the house and sat outside in the car with the window wound down, the bat detector switched on and waited for any bats to emerge. Timing is important so I arrived 10 minutes before sunset. Pip 55’s usually emerge around 20 mins after sunset, but its best to be early !

Sunset time was 20.24 on Tuesday 3^rd May and at 20.31 out popped the first Pip 55 bat and flew off in a southerly direction. The bat emerged from a gap in the soffit at the top of the gable end.  Pip bats are pretty small so any gap which is at least 8-10 mm wide will be enough. As well as hearing the bat I also saw it as the light was still good at that time. It was another 16 minutes before any more emerged, but at 20.47, after a bit of pre-flight chatter two more Pip 55’s popped out and flew along the lane towards the railway crossing. A minute later three more emerged, again flying in the same direction. Pip 55’s like to feed on insects around areas of water, rivers, streams, ponds, lakes etc and there are fishing lakes nearby and the River Medway about 2 Km away, so it’s not that far to travel for a  bat snack! The last three bats emerged at 20.51 and then that was it for the night, a total of nine Soprano Pipistrelle bats.

Pipistrelle bat in flight (Wikipedia)

In recent years the Pip 55’s have tended to meet up in this house, prior to finding additional local maternity roosts, so I am expecting numbers to rise over the next 4 – 5 weeks. I will post further reports in later in May / June, to report progress for the 2016 bat breeding season, but it’s great to know that the bats are still using this house as a roost.

Sunset serenade

Sunday 1^st May was a lovely warm sunny day, the first really warm day this spring, after an April which was dogged by cold winds from the north or north east for much of the month. Perhaps the weather pattern is changing and an overdue warm spell is heading our way. I do hope so.

Two weeks earlier I had seen the sun rise and listened to the dawn chorus in Foal Hurst Wood nature reserve, but I had been waiting for the right opportunity to hear the birds as they serenaded the closing of the day and settled down to sleep. Although it was too cloudy to see the sun set on Sunday it was warm enough for me to sit still in the wood for 75 – 90 minutes and listen to the chorus of birdsong, as the light dwindled.

Sunset was forecast for 20.20 BST, with dusk forty minutes later at 20.58 BST, so I arrived at the wood at 20.00 hours, as the performers were tuning up for the main event. Walking through the wood to my chosen spot I heard blackbirds, robins & wrens singing loudly from the many trees throughout the wood. I am sure it was just my perception, but the songs seemed a little less rushed and gentler on the ear than the dawn chorus two weeks earlier. Perhaps in the early morning there is an excitement to proclaim the new day, whereas a more reflective mood takes hold in the evening.

Singing wren (Gardenbirds.co.uk website)

After around eight or nine minutes I settled down in my chosen spot, towards the south western area of the wood. I had picked this area as it was further way from the traffic noise of the nearby Badsell Road, which was rather persistent along the northern edge of the wood. Many of the trees had burst their leaves in the last week or so, but the tree canopy was still rather bear, and so was not able to completely muffle the noise of passing cars. I reflected upon how busy this part of the UK is these days!

Singing song thrush (RSPB website).

Listening to birdsong is a little like hearing an orchestra. Some of the performers are loud and sing as if they are they providing a rousing solo performance, the Song thrush – Tudus philomelus -  is one such performer. Every note and phrase repeated three times at full volume, which tends to drown out other performers.  But robins & wrens, small that they are, were not prepared to give up without a fight and sung as if their lives depended on it. The blackbirds’ song was a touch gentler, and more melodic than its nosier cousin, a sweeter tune to hear.  These four bird species provided much of the performance, but one of the joys of sitting quietly in a hidden spot is that the wildlife becomes more accustomed to your presence and the more timid orchestral  members started to play their part, as they serenade the setting sun. Birds like the blackcap & chiff chaff,  who have travelled far to joined the woodland orchestra, provide fine performances that Sunday evening.

A pair of long tailed tits chirped gently for a brief moment and I suspect they had a nest with young, neatly hidden amongst the honeysuckle, draped around some of the birch trees close by.

Four goldfinch flew overhead, twittering noisily as they are want to do. The ‘tinkling triangles’ of the percussion section of the orchestra, maybe.

Two wood pigeons, bassoon players from the woodwind section, cooed gently in the background for around five minutes, all the while the song thrushes solo performance continued to belt out from high above, in the branches of an ash tree.

Further away, behind me,  I heard a pheasant clucking and clattering and crows cawing loudly, sounding like the cymbal had accidentally been dropped in the orchestras pit !  But it was no accident, for a few minutes later a blackbirds alarm call sounded loudly and stridently from the same direction, followed by a wrens alarm rattle. Something was afoot, possibly a fox starting its evening patrol.

It was by now 20.30 and the sun had set. Looking above me, tiny gnats were busily circling my head, attracted by my body heat and the promise of a free blood meal, given half the chance! All I could do was reduced exposed flesh to a minimum and flail away like a windmill, in a hope of keeping them away. Whilst I was busily swatting the gnats, as if on cue, two Common Pipistrelle bats (Pipistrelles pipistrelles) appeared in the woodland clearing in front  of me. ” Hurray, a pair of gnat nibblers”  I proclaimed to no one in particular; my problem might be solved !

Pipistrelle bat in flight (Wikipedia)

For the next ten minutes, in addition to the birdsong, I was privileged to have my own aerial display right above me. Like two spitfire pilots, the bats engaged in their own aerial duel with clouds of midges and gnats higher in the canopy, bent on capturing the flying morsels and filling their tummies with much needed food.

Singing robin (Saga website)

By 20.45 the birdsong had noticeably reduced, as the approaching cloak of darkness started to descend across the wood.  A few wrens and robins continued to sing, but the song thrushes solo performance had by now come to an end. The last songster, a robin, continued until around 20.55, but two minutes later the night patrol began. Two tawny owls started calling to each other across the wood !

I hung around for the next ten minutes listening to the two owl’s intermittent  ’ hooo, hooo, hoo-oo-oo-oo’ hooting and ‘kee-wick, kee-wick’ calls. One bird appeared to be stationary, on a tree near the edge of the wood, whilst the other was flying around and above the wood, judging by the moving sound. In this ‘400 year anniversary of the bard’ it is worth noting that it was Shakespeare who incorrectly wrote down the birds call as ‘tu-wit, to-who’.  It’s never one tawny owl making this sound, always two birds, one calling ‘Kee-wick’ and the other the gentler ‘hoo, hoo’ sound. This is the time for mating and nesting for tawny owls, as well as other birds, so perhaps I was listening to two lovers serenading each other in the still wood around me.

Tawny Owl (wwwfarm5.static.flikr.com)

I nice thought to end on, as I left the wood and returned to hustle and bustle of life in the town.

If you can’t rouse yourself for the dawn chorus, then an evening serenade is a very pleasant (and perhaps more achievable) alternative. Either way, visiting a woodland in the springtime, to hear the birds singing, should be an annual ‘bucket list item’, to boost your spirits and connect with the Earth’s natural rhythms.

Foal Hurst Wood in May