Recording Reed Warblers
By Philip Radford
This article was originally published in the Journal of the Wildlife Sound Recording Society Vol4 No1 Spring 1981
Someone remarked to me that reed warblers Acrocephalus scirpaceus are easy birds to record, so maybe that is one reason why I an attracted by their vocalizations. I do not use a parabolic reflector and I have never felt tempted to do so while recording reed warblers for the singing bird often remains at the same site for several minutes at a time. Nevertheless, I find the species a fascinating one and when, in late April or early May. I hear the bird's repeated jingle or medley of notes coming from the lakeside reed-beds I realise that springtime is really with us.
In appearance, reed warblers do not show conspicuous features: they differ from sedge warblers Acrocephalus schoenobaenus by the lack of creamy stripes above the eyes and also of the dark streaks of their backs and crowcs. Each bird has an unstreaked rump, tawny for the sedge warbler and rufous for the reed warbler. Superficially, however, the calls and song of both sedge and reed warblers have similarities. In the way, the songs of both blackcap Sylvia atricapilla and garden warbler Sylvia borin resemble eacn other; in apperance, both male and female blackcaps display their coloured head caps while garden warblers show brown for their abdomens and breasts. A bird whose appearazce is very much like thatod reed warbler is the scarce (in Britain at least) rnarsh warbler Acrocephalus palustris; this species now largely confined in distribution to the Severn Valley, has pinker legs than those of reec warbler but, on plumage characteristics, can only be differentiated with certainty by the wing formula. where song is concerned, however, the species do differ, particular in sound quality; marsh warbler's song is more varied, melodic and mimetic than that of reed warbler.
When reed warblers arrive in spring and the males attempt to establish their territories, they move to the old reed-beds where their plumage colouring matches that of the dead reed foliage. It is largely at this stage, or soon afterwards, that the cocks make their vertical song-flights, although this is not common behaviour and does not occur nearly as frequently as with sedge warblers. Reed warblers are individualists; some males indulge in short song flights while others are hardly ever seen above the tops of the reeds or other marsh or lakeside vegetation. Wihile cocks do not continue song-flights for long, the singing period is protracted and some birds sing well in mid-July or even early August. In contrast, male sedge warblers normally stop singing when, they have mated; if a sedge warbler is heard singing in June it is almost certain to be unmated at the time.
I get great pleasure in sitting concealed by a reed-bed in May as the green young reeds grow up to displace those which are brown and old. The pleasure is enhanced if a reed warbler is singing from thosereeds and even more so if I am making a satisfactory recording at the same time. True, a vigorous singing male is not difficult to record although ambient sound is a problem; where I listen for reed warblers song motor cycles, rabbit and pigeon shooting and chain saws are often in full activity soon after dawn. But pleasure is increased by natural background sound, for instance, by the barking, resonant calls of great crested grebe Podiceps cristatus, the splashing andloud one-syllable notes of coot Fulica atra, the explosive interjections of moorhen Gallinula chloropus or the evocative whinny of little grebe Podiceps ruficollis. Yet, to my mind, the most suitable accompaniment to reed warbler's song is the calling of the cuckoo Cuckulus canorus, uttered either in flight or perched on a nearby willow or poplar.
Of course, the research recordist wants his reed warbler sounds to be relatively uncontaminated and it is easier to get purer song later in the season when many lakeside birds have reduced their song output. But, if the evolution of song and calls is to be followed throughout the breeding season, recordings must be made from arrival to departure of the birds. Reed warbler song has repetitive components; phrases are repeated three or four tines and high-frequency sequences often alternate with harsher ones, As the season advances the phrases become more elaborate and the song quality is at its peak in July; during that month the duration of singing gets reduced and by the end of the month song is only sporadic, True late season song is given at a slower speed and phrases are often interposed with calls. With sedge warbler, the song has more harsh and chattering notes than with reed warbler but the overall musical quality and content is usually preferable, Marsh warbler's song is even more varied musical and has a higher content of trills,
I mentioned that individual cock reed warblers make song-flights early in the season; similarly, some birds, as they sing from a reed-bed, will climb up a reed until fully exposed to view. Other individuals, no matter how long they sing, remain concealed in the reed vegetation. When I do see a singing reed warbler climbing the reed stem to just below the flower while in full song, I am impressed by the amazing energy of the a.. with the warbler gently turning on the grasped reed, the bill is seen opening and shutting but remains open for most of the tine; the uttered song has repeated phrases but these are varied and many are complex and intricate. Judging by the chords which are emitted by some birds, it seems that the reed warbler has the ability to produce at least two notes simultaneously. It seems that there are reed warblers who specialise in whistling; I have recordings of high-quality whistled phrases which are incorporated into song of the more usual type. There is little doubt that whistling ability increases as the season advances.
Then some reed warblers, like many sedge and marsh warblers, are excellent mimics; again, as with whistling, there appear to be individual mimicry specialists. Of the birds imitated, I have found notes of the swallow Hirundo rustica to be the commonest; following this, calls of house sparrow Passer domesticus, blue tit Parus caeruleus, chaffinch Fringilla coelebs and blackbird Turdus merula are of ten featured although these are not placed in order of frequency. As would be expected, mimicry increases with the experience of the singer.
Turning now to anxiety and alarm notes, reed warblers give a short, rasping call which is quite characteristic; intensity and speed of delivery depends on the nature and urgency of the situation. The sedge warbler's alarm call is a hard 'tac' but with rather a wooden quality; when the bird is excited the notes are run together into rattles or churrs. Marsh warbler's alarm note, I understand, is similar but louder but I have not had personal experience of anxiety situations with this species,
For some years I have been interested in noting the behaviour of reed warblers when potential predators perch near their reed-bed territories or fly overhead. I have observed these responses on several occasions; a typical example is when a cuckoo flies over a large reed-bed, Perhaps I should clarify this: I am not suggesting that a cuckoo is a predator of reed warblers but it is a common nest parasite and, further, a cuckoo flying under certain conditions can look very like a sparrowhawk Accipiter nisus. Anyway, when this occurs, successive male reed warblers give vigorous bursts of song until the cuckoo has disappeared from view. Similar reactions happen if a carrion crow Corvus corone, a magpie Pica pica or a kestrel Falco tinnunculus should appear over the territory; it should be emphasised that alarm calls are not uttered. Instead, high-intensity song is just poured out as though in an act of defiance, which is probably the case. 3ut should a predatory bird actually perch in the centre of the territory, perhaps near a nest or flown young, then alarm calls are made, either by the male or female reed warbler or both may call together. Later in the season, the calls of young reed warblers can be heard, calls which are rather mournful or plaintive in quality.
I confess that if, in the course of reed warbler recording, I happen to come across a nest, I cannot resist a brief inspection. To start with, the cylindrical nest, which is built between three or four reed stems which be three or four reed stems whihc may be old or new or a mixture of both, is a distinctive structure in itself. The depth of the nest varies from just over 5 cm to 17 or 18 cm and on the soft lining of reed, flowers, hair and wool are laid four or five eggs of a dull green ground colour, blotched with grey cr brown. The nest is not always built between reeds or over water; it may be in willows, rose briers, brambles or almost any local vegetation The nest has no basket handles to support it as has the untidier nest of marsh warbler and which is commony built in nettles. Sedge warbler's nest is substantial and contains quite a lot of moss; it is usually sited in dense marsh herbage. Of course, a nest of any of these three warblers might contain a cuckoo's egg.
The recording of reed warblers' sounds over successive seasons has given me delight which has not always been ornithological. To sit, silent and contemplative, after having set up one's recording apparatus, gives an opportunity to admire the marsh plants growing around one. As daylight becomes full, so the bright yellow petals of the wild flag can be appreciated and, by July, reminded by the scent, the rounded reddish-blue flowers of water mint are opening at the end of their stems. In June, the lakeside is colourful with the red flower-spikes of bistort and the stiff, compact forms of purple loosestrife plants, topped by their red floral spires. Understandably, one gets bitten by marsh insects and, ignoring the cold of early morning, one gets used to water seeping through one's clothing. But when a reed warbler commences its song close to a carefully positioned microphone, then that is the reward for which one has been waiting. All too often, jet aircraft roar through the sky yet, with a modicum of luck, there may be some moments one can share alone with the reed warblers. These moments can be re-lived as they are played through, perhaps during a January blizzard, when the birds concerned are, one trusts, feeding or resting in their African winter haunts.