A paper from the British Ornithologists’ Union Records Committee The Dorset Yellow Tim Melling, Robert Y. McGowan and Ian Lewington Ian Lewington ABSTRACT A juvenile sinensis was found freshly dead at Radipole Lake, Dorset, on 23rd November 1962. At the time, the was dismissed as being a likely escape from captivity, but subsequent information on the potential for long-distance vagrancy in this and other small led to the record being assessed by BBRC and BOURC.The identification as Yellow Bittern was accepted by both committees but, as a result of anomalies with the bird’s plumage and the rather unusual circumstances of its discovery, BOURC rejected the record as a first for Britain.

n 23rd November 1962, at Radipole week later, on 30th November 1962, they took Lake, near Weymouth, Dorset, two local the bird to the Dorset County Museum, where it Obirdwatchers were approaching the was suggested that they send the skin to Dr John concrete bridge when a small flew across Ash, a member of the Rare Committee of the path some 50 m ahead of them. When they the Dorset Natural History and Archaeological reached the spot where the bird had disap- Society (DNH&AS), to confirm the identifica- peared from view, they found it, lying dead, at tion. According to the finders, the bird was the base of a concrete block, with blood drip- folded into a box before being posted to John ping from its bill. They described it as being ‘in Ash, as the skin had been prepared with wings the pink of perfection’ when they found it. spread, and would have been particularly cum- The initial reaction of the observers was that bersome to post without folding. it was an immature Ixobrychus John Ash showed the specimen to members minutus, and they skinned and dried the corpse of the DNH&AS Rare Birds Committee, who without delay. However, subsequent consultation noted that it showed a few features that were of The Handbook (Witherby et al. 1938–1941) wrong for Little Bittern. Since none of them led the finders to doubt the identification. A had sufficient literature or reference material on

© British Birds 101 • March 2008 • 137–141 137 The Dorset Yellow Bittern

other Ixobrychus herons, the bird was sent (on BBRC Chairman P. A. D. Hollom, Harber 17th January 1963) to the then British Museum replied, saying: ‘No, we do not feel that Yellow (Natural History) (BMNH) in London. There, Bittern can concern us, many thanks all the Derek Goodwin examined the specimen and same. But it makes one wonder what species are confirmed its identification as an immature kept in captivity – I certainly should not have Yellow Bittern I. sinensis. He noted that it dif- expected anyone to want to keep this bird.’ fered from immature Little Bittern in that: the top of the head was streaked rather than scal- Reasons for a review loped; the underparts were more streaked; the After being dismissed by BBRC in early 1963, coloration was generally more buffy; the wing the record was largely forgotten about. The only was much shorter; and the bill was longer. On contemporary documentation of the bird was a 28th January 1963, the specimen was returned mention in the proceedings of the DNH&AS by Ian Galbraith, Head of the Bird Department (Vol. 84: 63). In 1997, however, the record was at the BMNH, who commented that the bird included by Morrison (1997), who put forward must have escaped from an aviary, but also a case for it being a genuine vagrant; he sug- noted that Yellow Bittern was not a species gested that an escape from captivity or a ship- commonly kept in captivity. assisted passage were both unlikely possibilities. John Ash then contacted D. D. Harber, the In 2002, then-BOURC member Grahame BBRC Hon. Secretary. After consultation with Walbridge suggested that the record should be revisited in the light of what we now know about the vagrancy potential of small herons. Specifi- cally, a propensity for long-dis- tance vagrancy was apparent among a number of similar species (e.g. Striated Butorides striata and Green-backed Heron B. virescens, as well as Yellow Bittern itself (see below), while two Western Palearctic records of Schrenck’s Bittern I. eurhythmus preceded the Dorset Yellow Bittern). Another reason for a review was the lack of any evidence that Yellow were kept in captivity at the time of the record. Peter Coe Peter Yellow Bitterns are certainly not commonly kept in captivity, nor have they been in the recent past (Roger Wilkinson pers. comm.). Enquiries in 2002 revealed just two birds, both in collections in southeast Asia, although this was not an exhaus- tive search of private collections. It is difficult to ascertain captive status retrospectively, particularly as far back as 1962. However, the Zoological Society of London, renowned for keeping unusual species, could find no records of this species in their collections at Regent’s Park Zoo. It seems, there- Peter Coe Peter 82 & 83. The Dorset Yellow Bittern Ixobrychus sinensis. fore, that Yellow Bittern is a gen-

138 British Birds 101 • March 2008 • 137–141 The Dorset Yellow Bittern uinely unlikely species to be kept in captivity. October and perhaps until the end of Grahame Walbridge eventually managed to November (Carey et al. 2001). The species is track down the specimen, which had been monotypic and there is no evidence that migra- retained by John Ash and stored in his attic for tory northern birds tend to have longer wings, almost 40 years (plates 82 & 83); the specimen as might be expected. has now been deposited at the Natural History There have been several records of vagrant Museum (NHM), Tring, specimen reference Yellow Bitterns occurring well outside their number 2003.1.1. When handing over the speci- usual range. There is one fully documented men, Ash commented: ‘Soon after [the original record of a vagrant reaching Western Australia report], I heard that the finder had recently (in 1967), plus a further two, inadequately docu- returned from the Far East, as a result of which I mented and old records for Australia (Davies et considered the circumstances were too suspi- al. 1991). There are also two records from cious and that the record could not be taken seri- Christmas Island, which lies 500 km south of ously.’ There is no mention of this information in Java in the Indian Ocean (1978 and 1985) any of the contemporary correspondence, nor (Davies et al. 1991). A record in 1989 from Attu was it revealed in the comments of the two circu- Island, in the Aleutian archipelago, Alaska, con- lations of the DNH&AS Rare Birds Committee. firmed susceptibility to vagrancy well beyond Unfortunately, the two original observers could the bird’s normal range (Gibson & Kessel 1992). not be traced, although they were known at the To the southwest of its Asian range, it has been time to be members of the DNH&AS. reported from the Maldives (Rasmussen & Anderton 2005) and is a rare resident in the Sey- Distribution and vagrancy chelles, where there is a small breeding popula- Yellow Bittern has a widespread distribution tion. It has recently colonised Oman, where it which encompasses much of east and southeast was first recorded in 1984, but by 2003 there had Asia. Its breeding range extends from the Indus been 59 records, with a maximum count of six Valley in Pakistan and east throughout the low- individuals. Breeding in Oman was confirmed in lands of the Indian subcontinent south to Sri 2002 (Eriksen et al. 2003). There is also one Lanka, and through most of southern and record, in 1999, from the island of Socotra, eastern China north to central Heilongjiang Yemen, which lies off the Horn of province. It has been recorded from Sakhalin (Aspinall et al. 2004). Although extremely and the Kuril Islands in the Sea of Okhotsk, unlikely, it is therefore not impossible that a eastern Russia, but breeding has not yet been vagrant Yellow Bittern could reach Britain. proven here. In Japan, it is a rare breeding bird on Hokkaido but common throughout the The BOURC review south and into Taiwan. To the south it breeds Examination of the skin of the Dorset Yellow commonly throughout southeast Asia including Bittern, and comparison with other reference the Philippines and Indonesia, and east to New skins at the BMNH and the National Museums Guinea and New Britain. It has also colonised of Scotland, revealed that the bird had been in the Seychelles and has recently bred in Oman. juvenile plumage when it had died and had not Birds in the southern part of the range are yet started a post-juvenile moult. There is little largely resident, but those breeding in much of published information on moult in Yellow China and Japan join resident birds in southeast Bittern, or indeed in other members of the Asia in winter. A few, however, remain in genus Ixobrychus. Little Bittern does not begin southern Japan throughout the winter post-juvenile moult until reaching its winter (Hancock & Kushlan 1984) and the species is quarters, whereas Schrenck’s Bittern undergoes fairly common in Taiwan in winter. Returning post-juvenile moult prior to autumn migration. migrants reach Hong Kong, Guangdong However, the most unusual aspect of the Dorset province, from the last week in March, but first Yellow Bittern was the particularly dark pigmen- arrivals don’t reach Beidaihe, Hebei province, tation of its flight feathers (plate 84). Compar- until mid May and peak towards the end of the isons were made with 73 other juvenile Yellow month. Return passage through China is less Bittern skins in the NHM, Tring, and the pig- conspicuous as migrants and local breeding mentation of the remiges of the Dorset bird was birds occur together, but birds are still passing significantly darker than on virtually all of them. through Hong Kong until the last week in Only one other bird came close to matching the

British Birds 101 • March 2008 • 137–141 139 The Dorset Yellow Bittern

Dorset Yellow Bittern Juvenile Yellow Bittern in November Another anomaly was the width and shape of the flight feathers. The Dorset specimen had strikingly broad, square- ended primaries whereas all the other 116 Yellow Bittern skins examined at the NHM, Tring, had narrower flight feathers with more pointed tips (plate 84). The widths of

, © NHM,Tring the primaries of the Radipole bird were approximately 20% broader than those of other Yellow Bitterns examined

Ian Lewington (plate 85). This apparently 84. Comparison of primary pigmentation of the Dorset Yellow Bittern atypical feather growth is dif- Ixobrychus sinensis with that of another juvenile Yellow Bittern from the ficult to explain but is clearly Natural History Museum,Tring. not due to feather wear; the remiges of many of the other juvenile Yellow Bitterns examined were in pristine condition, just like those of the Radipole bird. A third unusual feature of the specimen was the method of preparation. Preparation of a bird skin normally involves removal of just the

Mid-primary width of muscles and tendons along the radius and ulna adult male Yellow Bittern (the bones that support the mid-wing). Both the radius and the ulna had been removed entirely from both wings of the Dorset bird, however, leaving no insertions for the second- aries. The finders also mentioned that they had skinned and dried the bird before taking it to the Dorset County Museum, just seven days after finding it. The bird was prepared as a flat skin, rather than as a standard ‘filled’ cabinet skin. The appearance was almost as if the skin , © NHM,Tring had been flattened by a large flower press, to Mid-primary width of little advantage other than that it could be Dorset Yellow Bittern stored in a confined space. The finders had few

Ian Lewington skills in preparing bird skins, admitting to ‘skin- 85. Comparison of the primary widths of the ning and drying it (not very well at that)’. It Dorset Yellow Bittern Ixobrychus sinensis and seems curious that they attempted this them- another juvenile Yellow Bittern from the Natural History Museum,Tring. selves, rather than take the fresh specimen straight to Dorset County Museum, especially colour, an individual collected in June, presum- since they thought it was a Little Bittern (or ably soon after it fledged. The only reasonable possibly something rarer) and therefore some- explanation for the flight feathers of the Dorset thing that would be of particular interest to the bird being so dark is that it had had little expo- museum. They also indicated that they had no sure to sunlight after fledging – for example, if it desire to keep the specimen, which also seems at had died while its plumage was very fresh or it odds with their efforts to skin and prepare the had been kept in captivity, away from sunlight. bird before taking it to the museum. Certainly, the plumage condition was not con- In addition to the above points relating to the sistent with that of a wild bird, exposed to specimen, there are several elements regarding natural light for several months and a journey the finders and the circumstances surrounding from east Asia to Britain. the discovery which caused the reviewers

140 British Birds 101 • March 2008 • 137–141 The Dorset Yellow Bittern concern. The observers claimed that the bird was found dead ‘at the base of a concrete block’. There are no concrete blocks at Radipole Lake but the concrete bridge still exists (plate 86). Many birds collide with wires and windows, which may be dif- ficult to see in certain conditions, but they rarely collide with highly visible solid objects. Yet the bill is in pristine condition with no scratches or chips. Death through such a collision seems highly unlikely, and the condi- Coe Peter tion of the bill is inconsistent 86. The concrete bridge at Radipole Lake where the Dorset Yellow Bittern Ixobrychus sinensis was reportedly found. with this hypothesis. On finding a dead rarity, most birdwatchers Roger Wilkinson. Particular thanks are due to Grahame would surely have taken the entire corpse to the Walbridge for tracking down the specimen and researching its history. We also thank BBRC for their review of the museum; the option of preparing the skin inde- identification, particularly Brian Small, who provided pendently seems particularly odd given that the detailed measurements and photographs of the specimen. finders had few taxidermy skills. If they had In addition: John Ash provided the actual specimen, plus extremely useful comments on the record; Peter Coe expected a long delay before the bird was allowed us to use his images of both the Radipole received by the museum, they might have pre- specimen and live Yellow Bitterns; Katrina Cook (NHM, pared it themselves to preserve the specimen, Tring) arranged access to the collections at Tring; Steve but they took it to the museum just seven days Dudley commented on early drafts of this article; Peter Summers provided expert comment on skin preparation after finding it. The report that one of the techniques; and Roger Wilkinson gave help and information finders had returned recently from the Far East on the current and former captive status of Yellow Bittern. is also, in the context of other anomalies, sug- gestive. It is extremely difficult to assess a record References such as this, when efforts to trace the original Aspinall, S. J., Porter R. F., & Al-Saghier, O. 2004. Four new observers have failed and it was not possible to bird species in Yemen from Socotra. Sandgrouse 26: 48–50. corroborate any of the facts. Nevertheless, the British Ornithologists’ Union (BOU). 2006. Records reported circumstances surrounding this record Committee: 33rd Report (April 2006). Ibis 148: 594. are certainly unusual, perhaps even suspicious. Carey, G. J., Chalmers, M. L., Diskin, D. A., Kennerley, P.R., Leader, P.J., Leven, M. R., Lewthwaite, R.W., Melville, D. S., BBRC assessed this record in 2003 and they Turnbull, M., & Young,L. 2001. The Avifauna of Hong Kong. confirmed the identification as a juvenile Yellow Hong Kong Bird Watching Society, Hong Kong. Bittern. They also commented upon the anom- Davies, J. N., Marchant, S., & Higgins, P.J. (eds.) 1991. alous shape and coloration of the flight Handbook of Australian, New Zealand and Antarctic Birds. Vol. 1: Ratites to Ducks. OUP,Melbourne. feathers, while the reported circumstances of Eriksen, J., Sargeant, D. E., & Victor, R. 2003. Oman Bird List. the record raised many questions. The record 6th edn. Centre of Environmental Studies and Research, was subsequently assessed by BOURC, who also SQU, Oman. Gibson, D. D., & Kessel, B. 1992. Seventy-four new avian accepted the identification, but it was not taxa documented in Alaska 1976–1991. Condor 94: accepted onto the British List because of the 454–467. doubts surrounding the record described above Hancock, J. A., & Kushlan, J. A. 1984. The Herons Handbook. (BOU 2006). Croom Helm, London. Morrison, S. G. 1997. Rare Birds in Dorset. Privately published, Dorset. Acknowledgments Rasmussen, P.C., & Anderton, J. C. 2005. Birds of South Asia. We are grateful to all members of BOURC, past and The Ripley Guide.Vol. 2. Smithsonian Institution and Lynx present, who have commented on this record and on Edicions,Washington, DC and Barcelona. drafts of this article: Colin Bradshaw, Martin Collinson, Witherby, H. F., Jourdain, F. C. R.,Ticehurst, N. F., & Tucker, Andrew Harrop, Chris Kehoe, Andrew Lassey, Eric Meek, B.W. 1938–1941. The Handbook of British Birds. Richard Millington, Steve Votier, Grahame Walbridge and Witherby, London. Tim Melling, Robert Y. McGowan and Ian Lewington, c/o RSPB, Westleigh Mews, Wakefield Road, Denby Dale, West Yorkshire HD8 8QD

British Birds 101 • March 2008 • 137–141 141