Saturday, 26 June 2010

Dancing on water

Watch the surface of a piece of deep and still water and you may be rewarded by the sight of the dancing shapes of whirligig beetles. Like shiny black beads, their glistening forms catch the eye as they whirl and gyrate across the water’s surface. This characteristic dancing motion provides both their common and scientific names; ‘whirligig or whirlygig’ and ‘Gyrinus’ respectively. They are quite remarkable creatures, able in the adult form to exploit the surface tension of the still waterbodies they inhabit, and they show a number of adaptations to this narrow world.

The larvae of these water beetles live below the water’s surface. Predatory in nature (as is the adult form) they breathe through filamentous gills, a feature that frees them from the need to return to the surface to breathe. This may be why they are able to exploit deeper waterbodies than other water beetle species.

The adult form has two pairs of highly modified legs in addition to a more typical (for a beetle) front pair. The hind and middle legs are much reduced, thickened and have strong hairs that fringe their edge. Watch a flotilla of these beetles and you get the feeling that they zoom across the surface in a seemingly smooth and mechanical manner. Of course, it is the legs that are doing the hard work. These operate like switchblades, snapping open on the forward stroke but then folding in on the return stroke to minimise resistance against the water’s surface. In human terms the speeds attained by these beetles would approximate to 180 miles per hour – quite an achievement! Another key feature is the way in which each eye is split horizontally, with part above the water and part below. This allows the beetle to detect prey and potential predators in either of its two worlds at the same time.

If you see a group of these beetles then you will almost certainly being seeing the Common Whirligig which, as its name suggests, is the most commonly encountered species. In fact, it is thought to be more common than all of our other whirligig species put together (there are a dozen different species in Britain). While some of these have restricted distributions, the apparent scarcity of the others may reflect their habitat preferences, with most preferring to live amongst dense emergent vegetation. One species, the Hairy Whirligig, makes use of both running and still water and is nocturnal in its habits. Even if you find one of these rare species it can prove difficult to secure an identification; most can only be reliable identified based on the shape and structure of the male or female genitalia. Best just to admire them from a distance then! 

Friday, 25 June 2010

After rain

After rain the countryside becomes a different place, the air refreshed and deliciously scented with sweet earthy odours released from the now sodden ground. The muggy, heavy air is gone and with it has gone the lingering drowsiness that tends to creep over me on these warm and sultry days. The greens of the vegetation seem darker, as if the leaves and fronds have absorbed the moisture through osmosis to become plumped up and fleshy. Droplets of water form on the vegetation; coalescing under the influence of gravity into larger drops they slip from the leaves to fall noisily through the canopy.

The beech trees are striking, their tall narrow trunks rising up to a green cathedral roof and stained darker grey by the rain. The trunks look like stone pillars and the regimented nature of their planting, with neat rows forming a thin veneer between the road and the brooding conifer plantation, only adds to the sense that I am within some wonderful piece of natural architecture. The closed canopy has so limited the growth of other plants that there is no field or shrub layer and my gaze through the plantation remains unimpeded.

Leaving the boundaries of the wood I slip silently out onto one of the wide forest tracks and then follow the line of power cables through the cleared ride. The grass here is long and unmanaged and, when dry, alive with various bugs (including the Bishop’s Mitre, a fitting species to find so close to the cathedral-like beeches). The grass itself is joyously wet and I delight at the way it tugs at my trouser bottoms and wets my shins. I am a child again, ignoring parental chidings about not getting wet, running through the meadows of memory with a broad smile on my face.

I can hear the soft calls of a party of Long-tailed Tits and it is not long before they are all around me, working their way back up the trail I have just followed. This is a family party, with youngsters in tow. These small birds, all fluffy feathers and lollipop stick tail, are a delight to watch. Some of the youngsters have wet plumage and appear bedraggled, further adding to their endearing character. The rain was heavy so I assume they must have taken shelter somewhere, only now venturing forth to search for small insects dislodged by the rain.

The heat will return; the vegetation will dry and the air will become increasingly heavy with moisture. Dark clouds will form, the atmosphere increasingly charged and I will become drowsy and wish for the inevitable storm to break. I can then look forward to that feeling of refreshment that comes after rain.

Thursday, 24 June 2010

Badgers show signs of activity

There are signs of activity in the wood, evidence that the local Badgers are busily engaged in their nocturnal wanderings. In some parts of the wood well-worn paths can be seen, striking across a particularly steep bank or out towards the pasture where they feed. Then there are the latrines, rough pits into which the Badgers defecate and which have an important role in social organisation and territorial demarcation. Elsewhere in the wood there is evidence of foraging activities, with ‘snuffle’ holes an indication of foraging for soil-dwelling invertebrates. A Robin’s nest has been ripped from the low bank in which it was hidden, the footprints of the culprit identifying a Badger as the predator involved. Ironically perhaps, the ripped out nest is lined with Badger hair, the Robin scavenging pieces of hair caught on a nearby fence under which the Badgers pass out of the wood and into the fields beyond.

The Badger has an interesting association with humans, in that pretty much all of us know what a Badger looks like (the image of a Badger features on the logos of numerous organisation and is used in the marketing of certain products). However, very few of us have seen a live Badger and many people live close to active Badger setts yet remain completely unaware of their existence. Badgers make frequent appearances on our television screens and you can even book yourself onto a Badger-watching wildlife break. The strong black and white face markings, the shuffling gait and the strong social ties within a group of Badgers, make them an engaging creature and it is easy to see why so many people have taken them to heart.

There is another side to our interactions with Badgers though, a darker side which has seen the Badger persecuted, baited and culled. Badgers were once persecuted because of their perceived impacts on game and fox hunting interests: the former because they opportunistically eat the young and eggs of ground-nesting birds and the latter because they supposedly compete with Foxes for access to earths and setts. They are still baited with dogs in some areas, a vile and inhumane practice that is thankfully becoming less common. Then there is the issue of Badgers and Bovine TB, which has controversially resulted in a controlled cull. Regardless of the role that Badgers may or may not play in the spread of Bovine TB, and of the need to protect the livelihoods of farmers, it does seem morally wrong to target a species purely because it has some impact on our lives. After all, such impacts are minimal compared to those we are having on the countryside and the other creatures with which we share it.

Wednesday, 23 June 2010

Varb Owls enjoy bumber start

It is quite an achievement. Thanks to the efforts of the local fishing syndicate, and support from EDF Energy, we now have Barn Owls again breeding on one of our local nature reserves. It is also quite an achievement for the owls, because the female is incubating a clutch of eight eggs. If all of these hatch then this will be one of the largest broods I have seen in a decade-and-a-half of watching and studying these magnificent birds.

The groundwork for such success was laid earlier in the year. While the provision of a suitable nest box has been particularly welcome, it has been the availability of small mammal prey that has enabled this particular female to produce such a large clutch of eggs. In turn, this highlights the importance of the habitat management being carried out on the reserve and the use of cattle to produce a grassland sward that can sustain such an abundance of Field Voles and shrews. For the owls, the real work will begin any day now, once the eggs hatch. Over the first week or so, the chicks will be unable to regulate their own body temperature properly and they will depend on their mother to brood them and keep them warm, the male bringing in food for the female to tear up and provide to the chicks. As the breeding attempt progresses, so the female will begin to leave the young unattended, helping the male to provide food for an increasingly demanding family.

Barn Owls initiate incubation once the first egg has been laid (most other birds don’t begin until the clutch is complete), with subsequent eggs laid at roughly two-day intervals. This means that the eggs tend to hatch over several days, resulting in chicks of different ages in the nest together. The eldest chick may be a week or more older than its youngest sibling. The adoption of this approach is very much a survival strategy, geared to increasing the chances that the owls will rear at least some young if times are difficult. It will be the oldest and largest chicks that will always get fed first, the youngest chicks only receiving food once the elder siblings are satiated. If food becomes scarce, then the youngest chicks will lose out and, unfortunately, are likely to starve to death. They then become food for the larger chicks. If all the chicks were the same age, then the chances are that they would all die if food became scarce. It may seem harsh but it is a neat strategy for a species whose prey may suddenly change in availability. Let’s hope that small mammals remain abundant on the reserve this summer.

Tuesday, 22 June 2010

Lack of reeds bad news for warbler

A pair of chest waders affords me access to the reedbed and, entering into its rustling embrace, I feel that I am in another world. The crowded stems, mostly of last year’s growth, remove horizons and play tricks with the limited perception of distance. This is a world dominated by sound, not least the soft drone of summer insects and the harsh staccato songs of Reed and Sedge Warblers. While most of the smaller reedbeds which fringe these old gravel pits are lush with new growth, this older bed is rather sparse. No doubt the emergent willow growth has had something to do with this, shading the bed and reducing the amount of standing water. Management work to remove the willow will not bear fruit until next year.

Each step forward is careful and considered. Not only do I have to be aware of underwater obstacles but also there are delicate nests in here. Little Grebe, Water Rail and Moorhen will use these beds for nesting, hiding their eggs within covered mounds of vegetation. Reed Buntings will tuck a nest away within the rough tumble of last year’s stems, compacted down by the winter snowfall. Then there are the low nests of Sedge Warblers and the more refined, woven nests of Reed Warblers that I am here to find and monitor.

Some of the nests had only been partially constructed on my last visit but are now finished and contain eggs. Some of the earlier pairs already have young; small, black-skinned and naked, they huddle helplessly in the nest, raising heads and bright gapes upon my approach, thinking I might be an adult returning with food. Reed Warblers tether their nests to reed stems and rely on this year’s growth for a solid support. As these stems grow, so the nest is transported upwards. Sadly, the lack of new growth has led one pair to attach its nest to a mixture of live and dead stems, the nest tipping precariously as the new growth pushes up beyond the single dead stem that has been incorporated. The chicks might just make it though, so short is their time in the nest (between a week and a fortnight from hatching).

Of course, the Reed Warblers face many other dangers. One of the most evident of these over recent days has been the Cuckoo, a female of which has been seen and heard around the reedbed. In fact, one of the nests in a nearby reedbed already contains a Cuckoo egg, its fate firmly sealed. Over the coming days I hope to see these blind and helpless chicks transform into bright-eyed, well-feathered youngsters ready to leave the nest and prepare for the journey south.

Monday, 21 June 2010

Wet alders home for Redstarts

The other weekend I returned to the southwest corner of Surrey, to the place where I grew up and in which I first developed my interest in natural history. This part of the county is known for its wooded beech hangers, dry sandy heaths and wet alder woods, collectively providing a mix of habitats of great quality. My passion for birds comes from happy youthful days spent birdwatching on these sites. A return visit was bound to deliver mixed emotions, not least because times (and habitats) have changed and because some of the bird populations have changed with them.

One bird that I was particularly keen to see was the Redstart, a cavity-nesting species associated with mature woodland and favouring the damp alder woods of some of my old haunts. An early morning visit to the Devil’s Punch Bowl at Hindhead, now in the stewardship of the National Trust, delivered the first pair of the day. The male was singing at the bottom of a gully that cut down into this rather steep sided valley; the female alarming close to the path was soon to be discovered feeding well-grown chicks in a rather open, and readily viewable, tree cavity.

Writing in 1544, Turner described how a Redstart might be recognised by the motion of its tail. This particular female demonstrated this feature to good effect, the brick red tail shivering as the bird perched near the nest, checking for predators before approaching to feed the young. Young Redstarts look not unlike young Robins or Spotted Flycatchers, their speckled plumage providing a degree of camouflage against numerous would-be predators. Throughout the remainder of the day we saw and heard several other Redstart pairs, suggesting a fairly good population remained in the area. The picture is very different here in the Brecks, where only a few pairs are to be found in the forest (although there are more on the army training area at STANTA).

One of the reasons that I find the Redstart so fascinating is because of a book that was published in 1950 as part of the famous New Naturalist series. The book was written by John Buxton and describes the results of his studies on the species, made while he was a prisoner of war in Bavaria during the Second World War. Buxton was a prisoner for five years and filled his time (or rather the summer months) watching and recording the behaviour of those Redstarts nesting around the various camps within which he was held. Buxton’s studies provide a clear example of how to develop an understanding of a species and its behaviour. One particular pair was watched for over 850 hours one spring, a staggering achievement.