Critique of an article: Little-known Oriental bird, White-eyed River-Martin Eurochelidon sirintarae

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Critique of an article: Little-known Oriental bird, White-eyed River-Martin Eurochelidon sirintarae by Joe Tobias, in Oriental Bird Club Bulletin 31; June 2000.

By Nick Upton 24/03/06

Research Techniques Assignment 1
BSc (Hons) Wildlife and Countryside Conservation, Year 2

Note: This essay is not intended to be a thourough scientific review of the known ecology of White-eyed River-Martin nor is intended to by an attack on the orignal article by Joe Tobias who I hope will be flattered to know that out of millions of articles I could have chosen to review it was his that interested me enough to do so. The remit I was given for this assignment was to choose an article from a peer-reviewed publication and write a balanced critique of it, with the highest grades given to those who are able to show a high level of critical thinking and originality. I have included my work here as I feel that some of the points I make will be of interest and may stimulate some thought upon the subject which in turn may contribute to rediscovering this species if it still exists; something that was also the intention of the original article which is reproduced here in the appendices with kind permission of the Oriental Bird Club (OBC) and referred to throughout the essay by paragraph number.

Please support the OBC's conservation work by visiting the OBC website and becoming a member.

Contents

1. Introduction
2. Literary Style
3. Factual Accuracy and Analysis
4. Conclusion
5. References
6. Appendices

Introduction

Figure 1: White-eyed
River-Martin (McClure, No date).

Even a cursory glance at one of the few photos in existence of the White-eyed River-martin (See figure 1) immediately conveys a feeling that it is a special creature, indeed, it has something about it that makes one wonder if it is in fact a real species and not a clever hoax. Add to this its mysterious discovery and disappearance, and the unusually low number of these birds that have ever been encountered, and the result is a bird of almost mythical proportions. This article attempts to clarify some of the facts that have become clouded since its discovery in 1968 (Thonglongya), to summarize the speculation surrounding its ecology and taxonomy, to rekindle hope that it may be rediscovered by proposing areas where it may persist and ultimately to introduce a new generation of ornithologists to a little-known and neglected species. To achieve this, the author employs a blend of historical narrative, extrapolation and speculation from scientific fact with an informal style of writing.

Literary Style
From the beginning of the article the author attempts, rather successfully, to create an almost fairy-tale like atmosphere, giving the reader an early sense of how mysterious this species is and by using vocabulary such as “spectacular”, “enigma”, “mythical” and “cryptic” from start to finish, the reader is constantly reminded of this theme. This element of mystery is created by placing the reader at the scene of discovery, making one feel part of the story from the first paragraph; setting the scene for suggesting that the reader has a part to play in the rediscovery of the species towards the latter stages of the discussion. By employing this style, the author has created a connection between the reader and the River-martin that not only results in reading the article to completion, but hopefully continues beyond by stimulating the reader to interpret the facts in their own way and to make further research into the subject. A discussive style of writing also helps to keep the reader at the centre of the article and by asking questions before answering them (Paragraph 7), it almost feels like one is having a conversation rather than reading an article. The system of referencing by numbers adds to this high level of readability, maintaining the flow of the argument without confusing the eye with large amounts of names in brackets or italics, although this is contrary to the system used by many authors.

These points all draw the reader further into the article once it has been commenced, but a certain aspect of the layout does not add to its attraction; there are no sub-headings to break the script into more digestible chunks for the reader with lower powers of concentration. It might be useful for the author to use headings such as “Discovery”, Ecology” or “Where to look” to give the reader an at-a-glance summary of the topic of each section. This is a minor point, but as it seems that widening the awareness of the White-eyed River-martin is an aim of the article it would seem sensible to employ tactics designed to attract as large an audience as possible.

Although the style of writing is largely excellent in terms of the atmosphere it creates and in its clarity, the second paragraph is uncharacteristically unclear in the way it attempts to explain that knowledge of the precise site of discovery may not be as reliable as is often stated. This is cleared up in the third paragraph, but it remains that the information in paragraph two is rather clumsily delivered. By using the words “Bung” and “Nong”, an assumption that the reader has some knowledge of the Thai language is made and this is ill-advised, further confusing the point, and when a poor translation is also used (fen would be more appropriate (Pers. Obs.; SE-Education, 2002; Phiromyothee, 2006)) it does not help the reader paint a clear picture of the site of discovery.

Paragraph two apart, the style of the article is interesting, it is easy to understand and very readable.

Factual Accuracy and Analysis
Before examining the factual content of the article, or any of the explanations it offers, it should be praised for bringing the story of the River-martin to a wider audience. If the reader is tempted to further his research on the subject, it immediately becomes clear how difficult this is to achieve with most of the referenced articles being difficult to obtain due to their age or storage in Thai libraries. In this respect, this article does a wonderful job of bringing the entire White-eyed River-martin story a new level of accessibility through the traditional media of scientific bulletin and, for the first time, through the internet.

The first nine paragraphs of the article outline the circumstances surrounding the discovery and disappearance of the species, and these facts are hard to dispute. Indeed, the author does a good job of questioning the accuracy of what has been long taken for fact, highlighting that the original research team never actually saw the species in the field (Paragraph 3). The author does, however, fall short of specifically pointing out that this included Kitti Thonglongya, who originally described the species (Birdlife International, 2001); this point would have given weight to the theme of keeping an open mind to the accuracy of some of the original reporting. Whilst speculating on the location of roosting Barn Swallows Hirundo rustica, and consequently where the River-Martin might be located, the author does well to highlight the changing ecology of Beung (Bung) Boraphet due to lotus harvesting (Paragraph 9), but completely omits to mention that the fen was totally drained of water in 1959 and 1972 (Jintanugool & Round, 1989) and again in the early 1990s (Stewart-Cox, 1995), with further disturbances during this latter period (Round, 1990). These facts have surely effected the stability of the ecosystem and could prove critical to whether the site remains suitable for White-eyed River-Martin. This section of the article also informs the reader that a reserve ranger was killed by poachers at Beung Boraphet; very useful in providing an insight into the problems of conservationists in Asia, as well as rather macabrely adding to the mystique of the narrative.

Figure 2: African River-Martin (Sinclair, 2004).

The remainder of the article discusses the possible ecology of this species in order to speculate upon where rediscover might occur, and in doing so draws the reader’s attention, in paragraph 10, to another little-known species, the African River-Martin Pseudochelidon eurystomina. As the closest relative of White-eyed River-martin this is a natural progression of the discussion, but despite providing excellent photos of sirintarae there is no image of eurystomina for comparison (See figure 2); whilst this is not a necessity it would be of interest to the reader. Having invited comparison with the African species, the author fails, at this point, to explore this line of thinking further, instead a summary of what can be inferred from the few specimens ever studied is provided.

These facts are of obvious merit, however, it would make sense to alert the reader to these before suggesting a look at African River-Martin and then to subsequently discuss its affinities to sirintarae in entirety.

Speculation based upon African River-Martin’s behaviour is made without properly discussing the most critical point when assessing the merits of this theme; in which genera are the two species to be placed? Mentioned in only fragmentary form, in paragraph four and in the penultimate paragraph, is the fact that some authors consider sirintarae deserving of its own genus and others consider it congeneric with eurystomina. To so briefly deal with this issue, and in broken fashion, would seem rather a pity, as the two species’ similarity, or difference, is vital when assessing the possible ecology and behaviour of White-eyed River-Martin; issues that are critical when speculating upon where it might be rediscovered due to the scarcity of factual information. Presumably this author considers that sirintarae should be placed in the genus Eurochelidon as this is the taxonomy used in the article’s title, but no explanation as to why this view has been taken is given other than a few anecdotal observations (Paragraph 4). Perhaps this is because this view does not really hold up to scrutiny; on re-analysis of the data taken from the original samples there is apparently no significant difference in the bill measurements of the two species (Zusi, 1978), previously the only non anecdotal evidence for different feeding ecologies and thus different genera (Turner & Rose, 1994). When it is also taken into account that the decision to place sirintarae in its own genus was based on data from just nine to twelve samples, certainly not enough to be conclusive, it may explain the author’s reluctance to discuss this issue. Whilst the author does well to encourage the reader to keep an open mind regarding the behaviour and ecology of White-eyed River-Martin throughout this section of the article, he might do better, considering the lack of evidence to the contrary, to concentrate on using African River-Martin as a model when considering the habits of the Asian species.

The article does in fact follow this theme up to a point, going on to propose regions that would most likely harbour this elusive species if it still exists, and this optimistic aspect is vital for the article to inspire any ornithological expeditions. Assumptions about sirintarae’s ecology here are indeed drawn from knowledge of African River-Martin in that large river systems (Turner & Rose, 1995; Birdlife International, 2000) are deemed the most likely regions to examine; with rivers in Thailand, Myanmar, China, Laos and Cambodia all suggested. The author does well to name the last of these as since publication there have been possible, if unconfirmed, sightings of White-eyed River-Martin there (Silver, 2003; Judell, 2006). However, this is simply recycling established views and although the stated aim is just this; “to compile our knowledge” (Paragraph 1), the author would be well advised to provide a new interpretation to improve the chances of achieving another stated aim; “in hope that it might lead to a dramatic rediscovery” (Paragraph 1). Indeed, it is here that the author, having made comparisons with the African species, stops short of further extrapolation; it is known that the African River-Martin breeds inland and migrates down the Congo river to winter in coastal regions (Birdlife International, 2000; Birdlife International 2005), so why not consider that the Asian species behaves the same? It has often been suggested that sirintarae might breed somewhere in China and migrate (Dickinson & Dekker, 2001), so the author does well to suggest the Salween, Irrawady and Mekong, but he would be well advised to consult an atlas to see that the Yuan in Vietnam would be equally likely (See figure 3). Indeed, this river, and the delta of the Mekong, would surely deserve consideration in respect of the number of scientific discoveries, and rediscoveries, in Vietnam since the end of the war. If beasts as large as the Vu Quang ox (Dung et al., 1995) and Javan rhinoceros (Newsweek International, 1999) can go unnoticed then surely there is hope for a bird as small and as mobile as the White-eyed River-Martin?

Figure 3: River systems that could harbour White-eyed River-Martin (Adapted from Microsoft, 2006).

A short article like this does well to touch upon, if sometimes too briefly, so many issues, and it may well be the intention of the author to simply provide a spark to rekindle a forgotten debate, and in this he has done well. One issue, though, does not seem to have been dealt with at all; the possibility that White-eyed River-Martin might only have ever occurred in Thailand as a vagrant, something others have subsequently proposed (Birdlife International, 2001). It is mentioned that the species was assumed to be regular in this country because the locals knew it by the name nok ta phong, “swollen-eyed bird”, however, this is a name so simple that it could have been made up on the spot by even a child, and carries no implication that it is a long-standing name. The article does observe, though, that rediscovery is most likely in another country, but by refusing to outline the possibility of vagrancy, denies the reader a vital clue to rediscovering the species. In this theme, the article could have gone on to suggest analysing weather patterns at the time of discovery in 1968 to see if anything unusual occurred. In fact, this reluctance to discuss vagrancy is perhaps similar to omitting a full discussion of taxonomy in its Siamocentricity, a line of thought that may have held back rediscovery of the species and may continue to do so.

The final paragraph of the article sees the author back to his best, with a splendidly optimistic and atmospheric summary of the likelihood that rediscovery will occur, pointing out the fact that it escaped ornithologists attention for a long period before being discovered. The last sentence, in particular, is well-designed to encourage the reader to further investigate the species and possibly claim his “prize”.

Conclusion
This article does an excellent job in collating the current knowledge of the species and revealing avenues of further thought that the reader might take when considering this species. The style of writing is interesting, upbeat and atmospheric, although at times the structure of the discussion does not seem as logical as it might. The author does well to draw attention to using the African River-martin as a comparison, but stops short of exploring the full range of possibilities this might lead to, even failing to recognise some of the basic inferences one might draw from this. There is also a failure to provide any conclusive evidence to explain why African and White-eyed River-Martins should not be considered congeneric; something that is at the centre of deciding upon their behavioural similarities or differences and consequently where the search for sirintarae might resume.

It can be said that the author achieves his stated aim of compiling current knowledge in an informative and thought-provoking way. By provoking the reader to question the facts, the author also goes some way to stimulating the road to rediscovery, but by not taking the opportunity to follow his train of thought to its conclusion he fails to make any ground-breaking speculation of his own to further this aim. Indeed, since publication a breakthrough has yet to be made (Butchart et al., 2005).

References
Birdlife International (2000). Threatened birds of the world. Barcelona & Cambridge, UK.

Birdlife International (2001). White-eyed River-martin Eurochelidon sirintarae, Red Data Book; Threatened Birds of Asia. Online at http://www.rdb.or.id/detailbird.php?id=257 [Accessed 21/02/06].

Birdlife International (2005). African River-martin; Birdlife Species Factsheet, Birdlife International website. Online at http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=70 [Accessed 22/03/06].

Butchart, S.H.M., Collar, N.J., Crosby, M.J & Tobias, J.A. (2005). Asian Enigmas: “Lost” and poorly-known birds: top targets for birders in Asia, Birding Asia-Bulletin of the Oriental Bird Club, No 3, June 2005.

Dung, V.V., Giao, P. M., Chinh, N. N., Tuoc, D. & MacKinnon, J. (1995). Discovery and conservation of the Vu Quang ox in Vietnam, Biological Conservation, Vol 72, No 3, pp 410-410(1).

Jintanugool, J. & Round, P. D. (1989). Beung Boraphet, Asean Regional Centre for Biodiversity Conservation (ARCBC) website. Online at http://www.arcbc.org/wetlands/thailand/tha_beubor.htm [Accessed 02/03/06].

Judell, D. (2006). Personal communication.

McClure, H. E. (No date). Photograph of White-eyed River-martin reproduced in Tobias, J.A. (2000). Little-known Oriental bird, White-eyed River-martin Eurochelidon sirintarae, Oriental Bird Club Bulletin 31; June 2000.

Microsoft Corporation (2006). Encarta Atlas online. Online at http://encarta.mas/encnet/features/MapCenter/map.aspx [Accessed 28/03/06].

Newsweek International (1999). In Vietnam, a Shot in the Dark (first photograph of the world’s most endangered animal, a Javan Rhino in Vietnam). Newsweek International, July 26, 1999.

Phiromyothee, S. (2006). Personal communication.

Round, P. D. (1990). Bird of the month: White-eyed River-martin. Bangkok Bird Club Bulletin, Vol 7, No1, pp10-11. Cited in Tobias, J. (2000). Little-known Oriental bird, White-eyed River-martin Eurochelidon sirintarae, Oriental Bird Club Bulletin 31; June 2000.

SE-Education (2002) SE- ED’s Modern English-Thai & Thai-English Dictionary (Contemporary Edition). SE-Education, Bangkok, Thailand.

Silver, G. (2003) Bangkok Morning/ Prek Tol, Cambodia Trip Report. Birdchat Website. Online at http://listserv.ccit.arizona.edu/cgi-bin/wa?A2=ind0302d&L=birdchat&O=D&P=3796 [Accessed 24/03/06].

Sinclair, I. (2004). Photograph of African River-martin reproduced in Trip report from Gabon, Sao Tome & Principe, and Camaeroon, 14 February – 11 March 2004, Tropical Birding website. Online at http://www.tropicalbirding.com/tripreports/STP-Cameroon-Feb2004FEW-pix.htm [Accessed 23/03/06].

Stewart-Cox, B. (1995). Wild Thailand. Asia Books, Bangkok, Thailand.

Thonglongya, K. (1968). A new martin of the genus Pseudochelidon from Thailand. Thai National Scientific Papers, Fauna Series no 1. Applied Scientific Research Corporation of Thailand, Bangkok, Thailand. Cited in Tobias, J. (2000). Little-known Oriental bird, White-eyed River-martin Eurochelidon sirintarae, Oriental Bird Club Bulletin 31; June 2000.

Turner, A. & Rose, C. (1994). A Handbook to the Swallows and Martins of the World, Christopher Helm, London.

Zusi, R. L. (1978). Remarks on the generic allocation of Pseudochelidon sirintarae. Bulletin of the British Ornithology Club, Vol 98, No 1, pp13-15.

Appendices
Appendix 1: Little known Oriental Bird: White-eyed River-Martin Eurochelidon sirintarae by Joe Tobias.

Paragraph 1 In January 1968, during the course of ringing activities at a wetland site in south-central Thailand, fieldworkers discovered a strange swallow amongst large numbers of migrant hirundines. It proved to be a new species and was christened the White-eyed River-Martin Pseudochelidon sirintarae by Kitti Thonglongya who dedicated this spectacular and beautiful bird to Princess Sirindhorn Thepratanasuda. Over the next three years several more specimens were collected at the same site, but apart from these, and a fleeting observation in 1978, this remarkable bird has effectively vanished. An avian enigma, it has come to epitomise the mythical allure of rarity to the birdwatcher, and for three decades it has symbolised the Asian mystery of the ornithological world. As such it has appeared in logo form in the pages of this journal as the archetypal little-known bird. The time has come to compile our knowledge of the species and to present it afresh in the hope that it might lead to a dramatic rediscovery.

Paragraph 2 To begin with, we need to retrace the events of January and February 1968 and glean what we can from the available facts. The site of discovery is first misleadingly given as a big marsh on the Chao Praya River (1). The type-locality is then specified as Bung (= Nong = Lake) Boraphet, Amphoe Muang, Nakhon Sawan Province, central Thailand (1), and from its subsequent description as a shallow, marshy, reed-filled lake of 25,000 hectares it seems clear that this is the big marsh originally mentioned (a point confirmed by Thonglongya (2)). Rediscovery efforts in 1980-1981 were apparently concentrated on an island where all of Kitti's river martins had been captured (3), suggesting that, at one time, confidence was high that a very precise origin was known.

Paragraph 3 This no longer appears to be the case. The first White-eyed River-Martins were reportedly caught while night-trapping roosting swallows (Hirundo rustica, H. daurica, Riparia riparia), wagtails and warblers by casting a fishing net over a reedbed (1) a method repeated by subsequent authors (3,4,5). However, according to a local technician who worked with the original field team, the birds were neither seen in the field nor trapped by any of the team members, but rather were brought in to the teams hotel in nearby Nakhon Sawan by villagers following a broadcast appeal for live wild birds for ringing purposes (6). It seems likely, therefore, that the precise site of collection is impossible to determine, but that it is certainly in the region of Bung Boraphet, and most likely at the lake itself.

Paragraph 4 Whatever their exact origins, nine specimens were initially collected: one each on 28 and 29 January (although the label on specimen 53-1218 actually states 27 January 1968 (6)) and seven on 10 February 1968 (1). From analysis of the resultant skins its closest ally was deemed to be the African River-Martin Pseudochelidon eurystomina (1). Initially described as congeneric (1), the African species and the Asian species differ markedly in the size of their bills and eyes, suggesting that they have very different feeding ecologies, sirintarae probably being able to take much larger prey and perhaps in different microhabitats (7). The gape of sirintarae is swollen and hardened, unlike the softer, fleshier, much less prominent gape of eurystomina(1,19). The feet and claws of sirintarae are unusually large and robust for an aerial feeder (1) and the two species also have different toe proportions, which might suggest dissimilar nesting habits (19). These differences are sufficiently pronounced in the view of some taxonomists to permit the allocation of its own genus, Eurochelidon (7), although other authors support the retention of both species in Pseudochelidon, arguing that they mirror patterns in other congeneric hirundines (8). Whether treated as one genus, or two, the syringeal structures of the two river-martins are divergent enough from those of the Hirundininae to confirm subfamily distinction from the true swallows, and apparently enough to suggest that they might belong in a separate family (1,9).

Paragraph 5 Shortly after these first specimens, a tenth bird was caught in November 1968 (2) and brought alive to Bangkok where it was photographed in December 1968 (3). Furthermore, at least two birds (one pair) reached but soon afterwards died in Dusit Zoo in Bangkok in early 1971 (3). The only widely reported field observation was of six individuals flying low over Bung Boraphet towards dusk on 3 February 1978 (10). In addition, four probable immature White-eyed River-Martins were reportedly observed perched in trees on Temple Island in Bung Boraphet in January 1980 (3,5), and one was reputedly trapped by local people in 1986 (11). Both these records remain unconfirmed. Several subsequent searches have tried to locate the species around the site. For example, eleven amateur birding groups surveyed the lake unsuccessfully during 1979 (3). Investigations were carried out between December 1980 to March 1981 by a team from the Association for the Conservation of Wildlife but, despite netting many roosting Barn Swallows in reedbeds, they failed to reveal any river-martins (12). In 1988 another concerted effort to relocate the species was undertaken at Bung Boraphet, ending with failure as the swallow roosts were highly disturbed and mobile (13).

Paragraph 6 The real number of White-eyed River-Martins trapped in the 1960s and 1970s may have been much higher than these figures suggest. In the wave of public and media interest following the sensational discovery of the species, trappers are rumoured to have caught around 120 individuals and sold them to the director of the Nakhon Sawan Fisheries Station (3,5). Moreover, local markets were reported to have had several other specimens in January-February of succeeding years (10). Having been found on Thai soil and decorated with the name of Thai royalty, there was a significant local demand for specimens or caged examples of the species, for zoos, presentation to dignitaries or as curios for the affluent.

Paragraph 7 What has become of the White-eyed River-Martin? Did this harvest of hirundines extinguish it entirely? Were these last known individuals merely the doomed remnants of a population displaced by disturbance from a specialised breeding habitat? (5) Perhaps. It is quite conceivably extinct, and if it still survives its population seems likely to be tiny. The original series of specimens taken in early 1968 were outnumbered by hordes of trapped Barn Swallows by a ratio of 9:6,000 (1). In spite of this exceptional rarity, it was thought that the species might be regular at Bung Boraphet since the local bird-catchers had a name for it, nok ta phong, the swollen-eyed bird (1). Unfortunately, there has been a drastic decline in the Bung Boraphet swallow population from hundreds of thousands reported around 1970 to maximum counts of 8,000 made in the winter of 1980-1981, although it is not certain if this represents a real decline or a shift in site in response to persecution (3). However, an estimated 100,000 swallows were present at a roost near Chotiravi, near Bung Boraphet, in August 1986 (11) and there were 30,000 at Bung Boraphet in May 1988 (11). Nevertheless, a dealer working the large Chotiravi roost claimed never to have encountered the species (11). The general feeling is that an absence of sightings since early 1980, despite numerous observational efforts, cast ominous doubts over the survival of the White-eyed River-Martin (3).

Paragraph 8 Unfortunately, the habits of swallows around the lake appear to have altered recently, with very few birds roosting in the reedbeds until late winter (13). Much of the population now roosts in sugar cane plantations, moving back to the reedbeds after the cane has been harvested (13). The roosts also form well after dark, whereas they once gathered before dusk (13). These changes are probably the result of prolonged disturbance by trappers (11). In any case, the swallow roosts are more mobile and difficult to locate, factors that have further obstructed the rediscovery of the White-eyed River-Martin.

Paragraph 9 The reduction in Barn Swallow populations in the Bung Boraphet area is difficult to explain but intensive trapping activities for the purpose of selling birds as food in local markets must have played a major role, as must the annual destruction of roosting sites to make way for lotus cultivation (3). Huge areas of reedbed in areas frequented by roosting swallows were being burnt in February 1986 (11). The hunting of hirundines without a licence has been illegal since 1972, although this legislation is rarely enforced (3). Relations between conservationists and bird trappers at Bung Boraphet are occasionally fraught, to the extent that a reserve ranger was killed when trying to apprehend poachers at roosts in 1987 (13).

Paragraph 10 It seems that any rediscovery efforts should now be targeted away from Bung Boraphet, and indeed perhaps away from Thailand. How might we judge where best to look? What secrets have hitherto been disclosed that might help direct our search? Unhelpfully, the ecology of this bird remains almost totally unknown, and thus ornithologists have looked to its presumed relative, the African River-Martin, to provide clues. Since P. eurystomina feeds largely over both forest and open grassy country, nesting colonially in tunnels dug in sandbars of large rivers (14) it has been inferred that E. sirintarae possibly does or once did the same (4). However, the differently shaped toes might suggest otherwise (19). At least one of the initial specimens had mud or sand adhering to its claws, and while this perhaps suggests a terrestrial perching habit (6), most swallows occasionally do the same, especially when collecting nest material. Another clue: in holding cages used during the swallow ringing programme, the birds stood quietly in the corner of the cage in strong contrast to other swallows which move rapidly from perch to perch calling repeatedly (1).

Paragraph 11 In the unconfirmed report of 1980, individuals were flying after insects with some Barn Swallows and sometimes perching on the tops of trees (20). During the 1978 sighting they were apparently skimming the water surface, possibly to drink (10). While these accounts describe behaviour characteristic of most swallows, the only direct dietary evidence is the fragment of a large beetle found in the stomach of a specimen (1). This fact, along with the mandibular morphology of the species, implies that it consumes sizeable prey.

Paragraph 12 What about breeding season, distribution and migratory behaviour? Five of the nine specimens collected in late January and early February 1968 were immature (1); they were later termed juvenile, and some of the other material as subadult (2) (although this is not mentioned in the original description). A breeding site within Thailand was initially considered plausible on the grounds that so many of the type series were young (2). It has also been speculated that if nesting occurs in Thailand it is most likely to do so between March and April, as this coincides with the local nesting season for the majority of insectivorous birds, while the monsoon rains from May onwards presumably raise water levels above the riverine sandflats postulated to be the favoured nesting habitat of the species (5,6,10). It is unlikely, however, that juvenile plumage would be retained for eight months, and thus these two facts are difficult to reconcile. The White-eyed River-Martin has otherwise been thought a non-breeding visitor to south-central Thailand (20) and clearly migratory (4), but these assumptions should also be treated with care. Although it has only been found between December and February, and despite the above disparity, there is insufficient information to rule out breeding in the Nakhon Sawan area (6,11). In conclusion, it is unclear whether the species is, or was, a migrant at all.

Paragraph 13 As recent searches around Bung Boraphet have been unsuccessful, let us assume it is a migrant. If it travelled across Thailand, where did it come from? The riverine nesting grounds might possibly lie along one of the four major watercourses (the Ping, Wang, Yom and Nan) which drain northern Thailand, either in the immediate vicinity of Nakhon Sawan or to the north (5,6). If it came from further afield, perhaps these putative breeding grounds lie on one of the other major river systems of South-East Asia, such as the Mekong in China, Laos or Cambodia, or the Salween and Irrawaddy in Myanmar (5,6). Evidence that the species breeds, or has ever occurred, in China is scant, although a painting by a Chinese artist held in the Sun Fung Art House of Hong Kong appears to depict the species (15). This tentative clue has failed to lead to any further information, and in any case the subject of the painting is more likely to be an Oriental Pratincole Glareola maldivarum (16).

Paragraph 14 A survey of the Nan, Yom and Wang rivers in northern Thailand was carried out in May 1969, but was not comprehensive and relied chiefly on interviewing villagers, none of whom seemed to know the bird (2). Rivers near the Chinese border of Laos were searched in April 1996, local people being shown illustrations of the species, but without success (W. Robichaud verbally 1997). Very few other surveys have looked for it outside Thailand and there is still scope for research in remote regions where a population might survive.

Paragraph 15 Throughout its possible range there is a catalogue of pressures potentially imposed on the species (5,6). Man has drastically altered the lowlands of central and northern Thailand: huge areas are now deforested, agriculture has intensified, pesticide use is ubiquitous and urban environments have spread extensively (5,6). In addition, all major lowland rivers and their banks suffer a high level of disturbance by fishermen, hunters, vegetable growers and sand-dredgers (5,6). Whole communities of nesting riverine birds have vanished from large segments of their ranges in South-East Asia owing to habitat destruction, human persecution and intense disturbance of most navigable waterways (5,17,18). Local people routinely trap or shoot birds for food and for sale in local markets (5,6). Even at Bung Boraphet Non-Hunting Area (established in 19793) the trapping of birds has continued, at some level, up to the present (5,6). If the species preferentially forages over forest, its numbers could already have declined to a perilously low level at the time of its discovery because of deforestation and the intensification of agriculture in river valleys (5,6).

Paragraph 16 These threats are based on the ecological traits inferred by its suspected taxonomic affinities. It should be borne in mind that riverine nesting habits and preferences for forest are only an assumption, and that it might conceivably utilise some entirely different habitat. Even the name river-martin is perhaps a complete misnomer, as the species has never been seen on a river and is no longer considered congeneric with the African River-Martin (7). Interestingly, the most recent scrutiny of specimens suggested that it was perhaps nocturnal, or at least highly crepuscular, based principally on its unusually large eyes (19). This raises the possibility that it is normally a cave dweller or a hole-rooster in trees or rock, emerging to feed in twilight or darkness, and this opens up new avenues of exploration. There are, for example, limestone caves not far from Bung Boraphet, and many more in Laos and southern China.

Paragraph 17 While there is only a faint chance that this, one of the most elusive species in the world (15) still survives, it bears the extraordinary distinction of being highly unusual in appearance yet overlooked by naturalists in a well-worked country until the late 1960s. As it is thus either extremely rare or inexplicably cryptic, it is not yet time to give up hope for the swollen-eyed bird. Its possible range should be revisited with a broader outlook. The prize, to any successful searcher, is considerable: solving one of the most puzzling mysteries of Asian ornithology.

References
1. Thonglongya, Kitti (1968) A new martin of the genus Pseudochelidon from Thailand. Thai
National Scientific Papers, Fauna Series no. 1. Bangkok: Applied Scientific Research Corporation of Thailand.

2. Thonglongya, Kitti (1969) Report on an expedition in northern Thailand to look for breeding sites of Pseudochelidon sirintarae (21 May to 27 June). Bangkok: Applied Scientific Research Corporation of Thailand

3. Sophason and Dobias (1984) The fate of the Princess Bird, or White-eyed River Martin (Pseudochelidon sirintarae). Nat. Hist. Bull. Siam Soc. 32(1): 1-10.

4. Turner and Rose (1989) Swallows and martins of the world. Bromley, UK: Christopher Helm.

5. Round, P. D. (1990) Bird of the month: White-eyed River-Martin. Bangkok Bird Club Bulletin 7(1): 10-11.

6. BirdLife International (in press) Threatened birds of Asia.

7. Brooke, R. K. (1972) Generic limits in old world Apodidae and Hirundinidae. Bull. Brit. Orn. Cl. 93: 53-57.

8. Zusi, R. L. (1978) Remarks on the generic allocation of Pseudochelidon sirintarae. Bull. Brit. Orn. Cl. 98(1): 13-15.

9. Mayr, E. and Amadon, D. (1951) A classification of recent birds. Amer. Mus. Novit. 1496: 1-42.

10. King and Kanwanich (1978) First wild sighting of the White-eyed River-Martin, Pseudochelidon sirintarae. Biol. Cons. 13: 183-185.

11. D. Ogle in litt. (1986).

12. Anon. (1981) A search for the White-eyed River Martin, Pseudochelidon sirintarae, at Bung Boraphet, central Thailand. Bangkok: Association for the conservation of Wildlife of Thailand. Unpublished report.

13. D. Ogle in litt. (1987-1988).

14. Keith. S., Urban, E. K. and Fry, C. H. (1992) The Birds of Africa, volume 4. London: Academic Press.

15. Dickinson, E. (1986) Does the White-eyed River-Martin Pseudochelidon sirintarae breed in China? Forktail 2: 95-96.

16. Parkes, K. C. (1987) Letter: was the Chinese White-eyed River-Martin an Oriental Pratincole? Forktail 3: 68-69.

17. Scott, D. A. (ed.) (1989) A Directory of Asian Wetlands. IUCN, Gland, Switzerland and Cambridge, UK.

18. Duckworth, J. W., Salter, R. E. and Khounboline, K. (compilers) (1999) Wildlife in Lao PDR: 1999 Status Report. Vientiane: IUCN-The World Conservation Union/Wildlife Conservation Society/Centre for Protected Areas and Watershed Management.

19. P. M. Rasmussen in litt. (2000).

20. Ogle, D. (1986) The status and seasonality of birds in Nakhon Sawan Province, Thailand. Nat. Hist. Bull. Siam Soc. 34: 115-143.