Blyth's Reed Warbler Acrocephalus dumetorum

At 0700 hrs. on 28th May 1984 B.R.Spence heard an unfamiliar song from a thick tangle of Sea Buckthorn in E side of the Point area. For the next 30 minutes, during which he was joined by N.A.Bell and M.G.Neal, the bird continued to sing. Eventually, it gave brief views in flight and, shortly afterwards, equally brief views at rest, when all that could be noted was that it appeared to have olive-grey upperparts, a poor superciliary stripe, a stoutish bill and a steep forehead. All three observers, tentatively suggested that the bird might be Olivaceous Warbler, though N.A.B., who had heard the bird in Israel, thought that the song did not ring true for Olivaceous. The song was rather slow, mimetic and with some quite melodic ‘pwee-pwee’ notes and more scratchy Acrocephalus/Hippolais “material”. It seemed the only way to identify it was to catch it. A mist-net was set up and, by 0800 hrs., the bird was in the hand.

The problem of the bird’s identity was not solved immediately it was caught. The tail shape was checked and seemed to be square, even though it was wet. Back at the Warren, this fact did not help the initial inquiries which were on Hippolais warblers in the B.T.O Identification Guide no 1. It looked as if it should be Olivaceous Warbler but the wing formula was not right. Upcher’s Warbler was too big. Could it be Booted Warbler? Then, while Svensson’s Identification Guide to European Passerines (third edition) was being checked , again for Hippolais, a footnote was seen to refer to the possibility of difficulty in separating the SE race of Olivaceous Warbler, H.pallida elaeica from Blyth’s Reed Warbler. Was the bird actually an Acrocephalus and not a Hippolais? The tail, now dried out was found to be rounded though not obviously so as it was slightly abraded. The third primary was checked and found to be slight notched on the inner web. This notch and the one on the second primary were measured; these together with the very short first primary clinched the bird’s identity as Blyth’s Reed Warbler

Description in the hand:

All upperparts, olive-brown with a slight green tinge, lesser and median coverts ditto, greater coverts ditto but lacking the green tinge; primaries, secondaries, tertials, primary coverts and bastard wing, browner with a very narrow olive edge to outer web; tail feathers ditto but without edge; fairly broad, buff-white superciliary stripe in front of eye, slightly narrower and browner over and behind eye; lores and short stripe behind eye, grey-brown; sides of “ face”, slightly paler than upperparts. Chin, throat and belly whitish, rest of underparts, off-white with breast and belly with some faint, very pale yellow-buff streaks and flanks washed with olive-buff. Upper mandible, dark horn; lower mandible, pale horn slightly pink and darkening towards the tip; legs and feet, grey-brown, with soles yellow-green; eye, dark; gape, yellow-orange.

When the bird was held outside for photography and viewing, the upperparts seemed much grey-brown with no green tinge than when seen close to inside, when being examined in the hand

Measurements:

Wing Formula:

When the bird had been “processed”, photographed and exhibited to the surprisingly large number of visitors who had “materialised” during the deliberations in the Ringing Laboratory, the question was where to release the bird. Ideally, a migrant should be released where caught but, in this case, this was out of the question if the waiting watchers were to have any chance of seeing the bird in the field. It was decided to release the bird into the hedge and bushes at the end of the ‘canal zone’ where the Thrush-Nightingale caught on 23rd was still claiming plenty of attention, where there seemed more chance of the Blyth’s Reed being seen and where it might, hopefully start to sing again. But, this was not to be. Unfortunately, as soon as the bird was released towards the W side of the hedge, most of the watchers present rushed right up to the hedge. Not surprisingly, the bird was lost at once. Followed by a line of people, it presumably went straight through the hedge and away. It was re-located about two hours later near Warren Cottage from where it was “pushed” , by the ever-increasing numbers of visitors, as far as ‘big hedge’ where it apparently remained for the rest of the day. It is not known whether anyone had more than the briefest views in flight or rest.

Later, a letter was received reporting a bird in song south of the Warren on 28th which was considered a Blyth’s Reed Warbler, after the observer had heard a recording of its song from the views he obtained of the bird. It is not known exactly where this bird was or when it was seen; presumably it was during the “lost” period. Or was there a second bird present?

Some comment on the behaviour of many of the visiting birders seems appropriate. There seemed to be a lack of fieldcraft. For people to run, often en masse, sometimes from more than one direction, to where the bird had been glimpsed, hardly helps anyone’s chances of seeing it in the field. Presumably, the sheer numbers of observers and the wish to see the bird made any accepted techniques impossible. A similar lack of fieldcraft was evident when visitors tried to see the Thrush-Nightingale in the hedge at the end of the ‘canal zone’. Surely, the way to see such a skulking species is not to stand right to the hedge, sometimes observers at both sides of the hedge and even lying under it. The Thrush-Nightingale, as other related species will do, often fed out in the open near to the ready cover of the hedge, when observers waited quietly at a reasonable distance, though the rushing tendency of a few when they were in the wrong place sent the bird straight back into cover. On 28th, even the Thrush-Nightingale was moved out of its favoured hedge for a time.