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Wildlife in Kingston

Tuesday 29 January 2013

Looking back to my very sketchy diary notes, I see that in mid-December, a few pipistrelle bats were evident at dusk around St Pancras Green, one group near the church and another in the opposite corner beyond the Pavilion. Then, exactly one week ago today, I was walking in warm sunshine in Friston Forest and watching a brimstone butterfly which had evidently emerged somewhat prematurely from hibernation. Song thrushes and dunnocks were in good voice all over Kingston and great spotted woodpeckers were drumming in the wood at the top of The Street: their own way of finding a mate and establishing a territory. A few primroses were already in bloom in the garden and daffodils were pushing up through the soft earth. Now, though, on 18 January (and way past the deadline for copy –  sorry Katie) the scene is completely transformed. It’s snowing hard, our small garden pond is frozen to a depth of several inches and the birds have fallen silent, having to concentrate on staying alive rather than pairing up. Wildlife in this country certainly has to be amazingly adaptable in order to survive.
Hibernation is one option for coping with winter; escaping it altogether through migration another. Bats in Britain select the first of these and are generally inactive between November and March. That said, sightings in December are not that unusual if the weather is especially mild.
The common pipistrelle –  the most likely bat to be seen anywhere - has two distinct types of roost, one for summer and another for winter. Summer roosts consist only of females and young, each bat producing just one baby a year. These roosts may be in crevices, underneath weatherboards or behind wall panels in buildings both new and old or occasionally in loft space: anywhere suitable, essentially, which offers both warmth and security.
Winter roosts, by contrast, are used by mixed sex groups of hibernating bats and therefore need to be consistently cool. Hollows in trees may be used as may caves and unheated buildings, which is why churches are so popular.
Pipistrelles are tiny. Their maximum length - about 42 mm from nose to tail –  is no longer than a matchstick and they weigh about the same as a two pence piece –  just 6-9 grams. The wingspan, though, is surprisingly long, at around 22 cm. Even so, a pip can, apparently, be fitted into a matchbox, although this is not something I have tried or would recommend to others!
Bats have developed a way of living that some humans –  those, anyway, who like a very quiet life –  might in some respects envy. They are active for only a few hours in every 24, mainly at dusk, and may spend around half the year asleep. The long periods of inactivity during a bat’s life may help to explain their relative longevity, with even pipistrelles often living for three or four years and larger, more robust bats considerably longer.
Although their active periods may be short, while they are awake pipistrelles may feed more or less continuously, consuming staggering numbers (perhaps 3000 prey items in a single session) of insects - mostly midges, gnats and small moths and beetles.
They hunt wherever their prey is likely to be plentiful: woodland edges, parks and gardens (especially those with water) and along hedgerows. They fly typically in the zone between head height and around 12 metres up, patrolling, like the now near mythical local Bobby, on a regular beat.
Bats, of course, locate insects (and avoid crashing into larger objects, such as people) by emitting ultrasonic pulses, detecting the echoes reflected back with their extraordinarily sensitive ears. Children and young adults can hear some of these calls but increasing age reduces the range of bat calls that are audible to us.
Bats are largely safe from predators as long as they restrict their movements to dusk, although some diurnal birds of prey like kestrels and hobbies do occasionally catch them. Very recently, a population of one species of pipistrelle (it is now known that there are three) was recorded as hunting consistently during daylight hours, a strategy that balances the greater risk of predation against the greater rewards available in terms of insect food. However, it is believed that local factors here make the bats relatively safe from predation.
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The cold weather should bring some unusual birds into gardens so do please keep a look out and let me know what you find.

Steve Berry