Monday, 20 May 2019

Otmoor Warblers 16th May 2019

Reed Warbler
May is the month when the numbers of breeding warblers on the RSPB's Otmoor reserve reach a zenith. Being a reserve primarily devoted to reeds and wet meadows fringed with hedgerow it attracts three species of warbler that are my particular favourites, the Reed Warbler, the Sedge Warbler and the Common Whitethroat. All three are summer migrants, coming here to breed and then migrating to Africa to spend the winter.
Reed and Sedge Warblers abound on the reserve. Common Whitethroats less so, due to less suitable habitat being available for them 

The Reed Warbler's  rhythmic, scratchy and  halting song, described by the original Handbook of British Birds as 'conversational' is first heard coming from low down in the dead reed stems of last year, that are only now being slowly superceded by this year's new growth of pointed leaves, rising up like grey green swords and that will reach the height of a man and conceal the warbler's nest, woven and slung like a basket between two stems of reed.

Sometimes the Reed Warbler will forsake the reed stems to sing in a small sallow or hawthorn adjacent to the reeds but never strays far from concealment in its favoured riparian habitat. Despite their loud song they are shy birds and if they sense you are looking at them or see you they will fall silent and drop down lower into the dead reed stems, then move invisibly to another nearby stem to resume singing.

Sometimes you can track their progress through the stems by the movement of individual reed stems and if you wait, see them sidle up and cling to another stem of reed, with one foot drawn up close to their body and the other extended below it in support, and recommence their repetitive singing. That is if they do not see you first!
Reed Warblers conduct their lives mainly in secret,  right from their first  arrival, through courtship, nesting and finally departure to their winter home in Africa, predominantly remaining out of sight, skulking amongst the density of the reeds and waterside herbage. The first intimation of their arrival on Otmoor is when the males commence singing, having literally arrived  one May night, dropping from a night sky, unheralded and un-noticed until they proclaim their arrival by singing from first light the next morning. The urgency of Spring and to reproduce paramount.


Today I  tarried by the side of  the bridleway looking down on a water filled ditch to catch sight of a male Reed Warbler that was singing loudly and persistently from a small sallow bush. It was very close to me but at first it was invisible to my eyes and took some minutes to locate, perched well inside the bush, its outline concealed and disrupted by the intervening stems and leaves, the latter casting sun dappled moving shadows across the tiny bird as they stirred in a gentle wind.

However a brief movement, a change of position, betrayed the warbler's location and I could then see it reasonably well, perched and moving its head around as it sang, its uniformaly rich brown upperparts and underparts of cream buff with a noticeably white throat, unremarkable, but perfectly matched for a life of concealment in the reeds. I stood in the sun and waited patiently for it to gain confidence. As long as it was quiet on the bridleway, I did not move, and no one else came along it would eventually reveal more and more of itself as it moved up a stem and nearer to the edge of the bush but never would it venture right into the open.

Its head appeared large as it sang lustily and continually, its rather long pointed bill held wide open showing orange inside and its white throat feathers distended with the effort of producing its song. For two hours I stood awaiting opportunities to take its picture and for all that time it was mainly singing. A few brief excursions along the water filled ditch interrupted the flow of sound but within a couple of minutes it would return to the favourite sallow and normal service would resume.

Reed Warblers on Otmoor are probably one of the main hosts of the Cuckoo and once the reeds are grown sufficiently and the nests constructed, the female Cuckoo will lay her single egg in a number of nests she has already been prospecting,  watching and waiting silently in a nearby bush or tree for the exact right time to deposit her egg in the Reed Warbler's nest.


Sedge Warbler
The other warbler inhabitant of the riparian habitat on Otmoor is the Sedge Warbler, although it is disinclined to frequent purely reeds but more prefers the margins of wet ditches where there is plenty of rank undergrowth, brambles, bushes or other tangled vegetation near to watersides. Where the Reed Warbler is shy and generally retiring, the Sedge Warbler is the opposite in the breeding season, singing loudly from an exposed perch at the top of a small bush or from a protruding stem of vegetation up which it ascends from cover to deliver its song which is superficially similar to that of the Reed Warbler but lacks the rhythmic quality of that bird.

The Sedge Warbler's song, as befits its extrovert personality is loud, long  and passionate, the notes coming in a chattering, buzzing, endless frenzy, seemingly at random and often incorporating the calls of other birds. Such is its extrovert personality the singer often takes flight, as if it cannot contain itself and, singing loudly, rises up into the air from its perch and then planes back down with wings and tail spread wide to the same  perch.

On Otmoor one early morning I discovered a particularly extrovert Sedge Warbler singing from the topmost spray of a briar by the pathway leading to the first screen and watched a bravura performance as, again and again, it rose into the air before returning to the briar, always landing a little way further down in the bush but then quickly ascending to the topmost spray before taking to the air for another paragliding song flight.

They are attractive little  birds, slightly smaller than a  Reed Warbler and less uniform in colour, with long cream eyebrows, a cap of dark streaking and tawny upperparts streaked with black and darker brown, their undersides creamy white becoming buff on the flanks.

All over the reserve their frantic chattering songs come from hedgerows running by channels of water and wet ditches and the occasional bird floats down from a song flight as I wander along the paths of the reserve. The whole place is alive with the songs of both Reed and Sedge Warblers and it is a delight to see the reserve now come alive and to be serenaded with song from these marvels of creation that have made a perilous journey from far overseas to bring such pleasure to me and other visitors.

Common Whitethroat

So finally we come to the third warbler, the Common Whitethroat, which is much less frequently encountered on the reserve at Otmoor than the previous two warblers, due to the fact that their preferred habitat, dry untended field borders, thickets and rough ground with tangled vegetation is less available. Mind you, where it is, then there will be found and heard the male Common Whitethroat singing his jaunty song - a short, lively jumble of cheery notes, repeated over and over and delivered from an exposed spray of vegetation or in a wild dancing song flight of pure ecstacy or so I like to think.

Along the same pathway where I described the extrovert Sedge Warbler singing, just  a little way further was a male Common Whitethroat behaving in exactly the same way. I do not know what it is about this path that persuades the warblers to be less fearful, maybe it is the constant procession of people walking to the first screen but whatever, it is a delight to be able to get so close to these birds and to freely watch them.

The whitethroat was singing from a hawthorn right by the track and at first I was circumspect, maintaining a distance so as to not alarm him as he sang. I edged closer and he did not budge. A bit closer yet and all he did was ascend higher up the spindly twig he was clinging to until he was outlined against the sky. He sang on, opening his bill wide and tilting his head upwards for maximum effect. Then a short period of silence followed before he sang again.

Emboldened by the whitethroats lack of concern I walked closer still until I was almost underneath He looked down, curious but unafraid, cocking his head and then raised up his bill and sang to the heavens once more.

I was of no apparent concern to him and we shared a few moments together before he decided he would like to sing from another perch further down the pathway but less exposed. I walked past the whitethroat but now hidden inside a bramble and still he sang as I left him.

I fell to thinking about the frankly incredible journey this bird had made to unknowingly charm me with his song and confiding nature. Some years ago its fantastic journeying was brought home to me in vivid fashion when I encountered one spending its winter in Tanzania. Both of us so very far from home. The perils of, especially, a migrant bird's life are many and years ago when a young man I can remember one Spring awaiting the return of Common Whitethroats to my local study area in Surrey but they never came. Where there had been seven pairs of Common Whitethroats now there was none. It was 1969 and no one knew quite why they had failed to return not only to my small study area but as it transpired nationwide. A year later it was determined that severe drought in their wintering area in The Sahel  had decimated the wintering birds and it took some years for their numbers to recover

So we may call it a Common Whitethroat but it can just as easily not be so and birds in general are far less in number now than they were fifty years ago.

We must never take the delights of Otmoor for granted, be they the warblers or any other of the splendid and scarce birds that occur there. Otmoor and its like provide a last remaining sanctuary in an increasingly hostile environment for the natural creatures that inhabit and share our planet.

We are indeed lucky to have them still but for how much longer?

Thursday, 16 May 2019

Pearl Borders and Burgundys 13th May 2019

Monday brought the promise of all day sunshine and my thoughts turned to Sussex and butterflies. Now is the time that two favourite butterflies of mine fly and I had two locations in mind where I would go to look for them;  Kithurst Hill near Storrington for the tiny but beautiful Duke of Burgundy and Rewell Wood near Arundel for the larger but just as desirable and equally scarce Pearl bordered Fritillary.

Like many of our butterflies both are endangered and require intense habitat management on special reserves to keep them from dying out. Such a shame it has to be like this but that is the way of it these days as land management methods become ever more incompatible and hostile towards the natural world.

My first stop was at Kithurst Hill which lies at the top of the West Sussex South Downs and where the South Downs Way crosses from east to west.  Kithurst Hill is a north facing slope looking over the Sussex Weald towards the distant haze blue bulk of the North Downs.

A slightly chilly southerly wind was blowing at the top but by walking down the cowslip festooned slope it became warmer  at the bottom, a sun trap, sheltered as it was from the wind
The bottom of the bank on Kithurst Hill

Cowslips - the Duke of Burgundy's larval foodplant
It was almost noon and the heat from the sun had reached a sufficient intensity to persuade the butterflies that inhabit here to commence flying. A couple of Dingy Skippers were first to appear, and never does a butterfly live up to its name as does this one! Unremarkable and drab beyond measure these butterflies still retain an elusive charm as they whirr around on wings that move so fast they are a blur. They settled on the hard spherical heads of Salad Burnet, with their wings spread to absorb the sun but they have a curious habit of then slowly retracting their forewings partially over their hind wings so the butterfly takes on a triangular form. I thought this hitherto un-noticed characteristic might just  have been  an isolated occurence with one particular individual but all the others I observed performed this curious movement once they had settled. 

Dingy Skipper
I have seen many Duke of Burgundys, so should not be surprised at how small they are, but I confess to always being taken aback each year as I first see their tiny dark brown forms scudding low across the downland grasses covering the warm chalky earth. Two males spiralling in combat were the first  I saw but they soon separated, each to settle apart in the sun, their dark brown wings chequered with amber markings and their underwings showing exquisite asymmetrical panels of white.

Duke of Burgundy
A miniature masterpiece that will be alive for a few days and then die. How can it be that something so beautiful has such a very brief existence in this the last and most attractive stage of its life? I found another individual crawling amongst some primrose leaves, the larval food plant, delving deep into the dark recesses at the coswslip's base.It was a female, its abdomen distended and bulging with eggs which it was laying as quickly as possible. No time to lose in her brief existence. She bent her abdomen under a selected primrose leaf and deftly deposited an egg on the underside of the leaf. Very precise and particular before moving on to another leaf to repeat the process.

Duke or should I say Duchess of Burgundy laying eggs
She flew and I lost sight of her against the slope but a fellow enthusiast found a pair mating, the two insects hanging from a grass blade in union. Nothing would part them and for well over half an hour they consumated their liason, moving regularly along blades of grass and even falling onto the ground at one stage but never for an instant did their two conjoined bodies separate. I became anxious for them as they lay on the ground.

Mating Duke of Burgundy

They could easily be trampled by someone wandering around unaware of their presence, so small and inconspicuous were they in the grass. I placed my finger under one of them which promptly walked onto it  bringing the other butterfly with it. I transferred them onto a blade of grass on the mound of an ant hill where they would be safer from unwary feet.

More enthusiasts began to arrive, not many but enough to persuade me to go and seek a quieter area and find some Dukes all to myself. I walked back a short way down the approach lane and on the high banks on either side, again full of cowslips, I found a freshly emerged Duke and sat in the sun admiring its perfection, and then I found another.The secret is to just wait and eventually they will fly and reveal themselves, being usually a male patrolling its small territory.

There were of course other butterflies here, diminutive Brown Argus their wings outlined in orange spots, Common Blues, an indescribable shade of blue in the bright sunshine, large citrus yellow Brimstones looking huge to my eyes after peering at the smaller butterflies and finally a Green Hairstreak,  an emerald triangle of closed wings angled to the sun, sat enthroned on a hazel leaf in a  secluded corner by the car park.

Brown Argus
Common Blue

Green Hairstreak
It was now mid afternoon and time for me to head to my second destination, Rewell Wood and hopefully renew my acquaintance with the Pearl bordered Fritillarys whose habitat management there is being supervised by Neil Hume of Sussex Butterfly Conservation and  which requires a three year rotational coppicing, courtesy of a lot of hard work during the winter months by volunteers and  the permission of the Duke of Arundel who owns the commercially harvested wood.

Part of Rewell wood that has been coppiced in readiness for
next year, 2020

The coppiced habitat frequented this year by the fritillarys

Commercial forestry operations
It had become a glorious afternoon of sunshine and parking the car in the tiny layby off the busy A27 I walked the access track through the wood to where it joined the wide ride crossing it and along which are the three coppiced areas that provide a home to the Pearl Bordered Fritillarys. The western and middle thirds were where I saw them last year but when I met Neil Hume last year he told me that this year the butterflies would be in the eastern third as this would be the most suitable habitat for them..

Initially I saw little sign of any butterfly but then after no more than a minute a Pearl flew low over the bare ground past me, and then looking down onto an insignificant patch of blue purple Bugle which the Pearls love to nectar on,  there was another, half hidden,  its ginger wings covered in black spots and squiggles, nectaring deep at the base of the flower.

I walked on and a succession of Pearls came flying across the bare strip of ground I was on, or flutering out from the coppiced trees further in. Others were basking in the sun or nectaring on the Bugle flowers. I was seeing dozens of Pearls, a veritable bonanza of this rare and threatened butterfly and this year they seemed inclined to remain in one spot for more than a few seconds.

The string of white pearls on the outer edge of the underwing from
whence the butterfly derives its name

This individual had three symmetrical white tips on each hindwing

Last year they were frustratingly and continually flying and not settling until late in the day. Neil  had told me they were males looking for females but this year there was not so much evidence of this continual quest for females

Pearl bordered Fritillarys
I did find one very tatty and presumably male Pearl harassing a perched female but she continually quivered her wings, the equivalent of a female Pearls brush off, so presumably she already had been mated or was not ready to mate yet. The male gave up and flew off.

The only other butterfly species I found were a couple of delightful Small Coppers which were in pristine condition and obviously hatched recently, possibly just today.

Small Copper
I walked the ride up and down on several occasions and was pleasantly surprised to have the place entirely to myself. I saw not another soul for the whole two hours I was there.

The gentle solitude of the wood, punctuated by a Garden Warbler's rich song and Blackbirds singing gently from deeper in the wood set the mood and it was with heart uplifted that I left Rewell Wood and Sussex in the early evening sunshine.