A paper from the British Ornithologists’ Union Records Committee Records of Hawk Owls in Britain Ben Green Andrew H. J. Harrop Abstract As a consequence of a recent review by BOURC, there are now just four accepted British records of the Hawk Owl Surnia ulula. A bird of the North American race S. u. caparoch, found in an exhausted state on board a ship off the coast of Cornwall in March 1830, remains the first acceptable British record. The other three records, two of which date from the late nineteenth century, involve the nominate race, which breeds in Scandinavia. The only recent record refers to a bird in Shetland in September 1983, and this Hawk Owl remains on Category A of the British List. A summary of racial identification and ageing is presented, and taxonomy, distribution and irruptions are discussed briefly. s part of its ongoing work on the British List, BOURC aims to determine the first acceptable record of each taxon. In the case of the Hawk Owl Surnia ulula this required a review of all the previously accepted records. Following two circulations, many of these records were A 276 found unacceptable, for reasons which are explained here. There are now just four accepted British records, one of the North American race S. u. caparoch (hereafter caparoch) and three probably or certainly of the Eurasian breeding form S. u. ulula (hereafter ulula). © British Birds 103 • May 2010 • 276–283 Records of Hawk Owls in Britain Historical status in Britain fraudulent, collector of rare and unusual birds and, unsurprisingly, they were not recorded at the time, so subsequent authors suspected fraud. One of these Hawk Owls is now at the Booth Museum, Brighton (accession number BC207259), and is identifiable as ulula on the basis of the pattern of the underparts (see below) (www.virtualmuseum.info/collections/object. asp?searchText=hawk+owl&ckid=377867& row=5&view=1). Another caparoch, said to have been obtained on the north coast of Ireland in 1910, found its way into Harpur Crewe’s collection in 1914 and has never been formally accepted. There are also references to very small numbers of this species in captivity (e.g. Alexander & Fitter 1955, Cage & Aviary Birds 12th June 2008), but birds of captive origin were not considered likely to be involved in any of the records reviewed here. Despite this species’ distinctive appearance, the identification of two sight records formerly accepted by BBRC is no longer con143. Upperside of five specimens of Hawk Owl Surnia ulula. From sidered acceptable: on the left to right: S. u. caparoch from Canada; dark immature S. u. ulula from Bleasdale Fells above ChipSweden; typical S. u. ulula from Sweden; S. u. ‘pallasi’ from Kultuk, ping, Lancashire, on 13th Russia; and S. u. tianschanica from Aksu, Turkestan. September 1959 (Brit. Birds 92: 585), and at Gurnard’s Head, Cornwall, on 14th August 1966 (Brit. Birds 101: 551). Taxonomy and distribution Andrew Harrop © NHM, Tring Andrew Harrop © NHM, Tring The Hawk Owl has been judged a rare vagrant by all authors who have discussed its status in Britain. Some (e.g. Saunders & Clarke 1927) have considered records of caparoch likely to involve ship-assisted birds, but until now there has not been a full systematic review of all records. Several older records of this species have been associated with fraud. Wood (2007) listed three allegedly taken in Essex in February 1913, which found their way into Sir Vauncey Harpur Crewe’s collection. Harpur Crewe was a notoriously uncritical, and perhaps 144. Underside of five specimens of Hawk Owl Surnia ulula. From left to right: S. u. caparoch from Canada; dark immature S. u. ulula from Sweden; typical S. u. ulula from Sweden; S. u. ‘pallasi’ from Kultuk, Russia; and S. u. tianschanica from Aksu, Turkestan. British Birds 103 • May 2010 • 276–283 The Hawk Owl is conventionally placed in a monotypic genus, with three subspecies recognised by Cramp (1985). Siberian populations, formerly separated as a fourth taxon, pallasi, are now included within nominate ulula by this treatment. The nominate form is found from northern Europe east 277 Harrop through Russia to Kamchatka and Sakhalin and in central Siberia south to Tarbagatay; S. u. tianschanica occurs in central Asia and northwest and northeast China; and caparoch from Alaska through Canada to Newfoundland, and south to extreme north USA. Among several other bird taxa, what were formerly regarded as different subspecies in the Old World and New World have recently been reclassified as separate species on the basis of significant genetic differences (Koopman et al. 2005) – for example, American Picoides dorsalis and Eurasian Threetoed Woodpeckers P. tridactylus, Black-billed Pica hudsonia and Eurasian Magpies P. pica. The Hawk Owl is relatively poorly studied and it is likely that comparable genetic differences exist between Nearctic and Palearctic populations, although this remains to be confirmed. Movements and irruptions All populations of the Hawk Owl are nomadic, moving in response to food availability and climatic conditions, with a cycle that follows that of rodent prey. Irruptions may occur when vole populations crash, at 3–5-year intervals. The earliest date for significant autumn movement by caparoch is 15th September; most move between mid October and late November. Movements of ulula begin in early September and peak during October–November. Periodic irruptions have been recorded during the twentieth century for both ulula and caparoch. It is known that those in Europe have involved large numbers of juveniles (85% in one Swedish study; Edberg 1955), that distances of up to 1,860 km have been covered, and that the Baltic forms a significant barrier to dispersal. It is notable that there were only two records from the Netherlands during 1800–1999 (van den Berg & Bosman 2001). In North America, females and juveniles are known to move earlier and farther than adult males. All states of the USA with accepted records are in the north, and the few ringing recoveries there involve distances of up to just 259 km from the ringing site. There is, however, a recorded movement of 3,187 km by a bird ringed in Canada in February 2000 and recovered dead in Alaska during October of the same year (per Bird Banding Office, Canadian Wildlife Service). Raymond Barlow Racial identification and ageing 145. Hawk Owl Surnia ulula of the North American race S. u. caparoch. Separated from ulula by the darker and greyer colour to the facial disc, darker ground colour of the upperparts and upperwing-coverts, which show smaller white feather tips, and broader black barring on the flanks and across the upper breast. Note how snowy conditions make the ground colour of the underparts appear paler than normal. The identification of Hawk Owl taxa has been discussed elsewhere, notably in Cramp (1985). The following discussion is based on a study of skins at the Natural History Museum, Tring (27 ulula including 9 ‘pallasi’, 8 tianschanica and 41 caparoch), photographs and the literature. It was established that tianschanica is doubtfully distinguishable 278 British Birds 103 • May 2010 • 276–283 Raymond Barlow Records of Hawk Owls in Britain 146. Hawk Owl Surnia ulula of the North American race S. u. caparoch showing the underparts and underwings. Note the relatively heavy dark barring on the underparts of caparoch, which is of more consistent width than on ulula. In addition, the underwing of caparoch appears darker than that of ulula, in part because the barring on the underwing-coverts is darker and broader, but also because the white ovals on the outer primaries are smaller and narrower, often completely encircled by the darker colour of the feather, giving a more spotted appearance than ulula. See main text for further details on the differences in the pattern of the barring on the flight feathers between the two races. identifiable to taxon. Of the differences described in Cramp (1985), the most useful are that caparoch shows a blacker ground colour to the upperparts and upperwing-coverts, with smaller white marks; a distinctly broader, blackbarred band across the upper chest; and David Tipling from ulula except by measurements; since it is a highly unlikely vagrant to Europe, it is not discussed further. The main findings are that caparoch is rather consistent in appearance; that ulula is more variable, with darker individuals close to caparoch in appearance; and that typical individuals are readily 147. Hawk Owl Surnia ulula of the Eurasian race S. u. ulula. In comparison with caparoch, the facial disc and underparts are whiter, and the dark barring on the breast is narrower. In addition, the white barring in the primaries is of similar width to the adjacent dark barring, and is not encircled by it as is the case with caparoch, thus giving a more barred appearance. Compare the underparts and underwings with those of the North American caparoch in plate 146, above. British Birds 103 • May 2010 • 276–283 279 broader dark bars on the breast, belly and flanks (2.5–3.0 mm in caparoch compared with 1.5–2.5 mm in ulula) that are tinged rufous. In addition, the ground colour of the facial disc and underparts of caparoch has a greyer cast than the typically much cleaner white of ulula. When the underwings of specimens or good digital images are compared, caparoch consistently shows heavier, broader brown barring on the underwing-coverts combined with a distinctive pattern on the outer primaries. The white ovals on the outer primaries are often completely enclosed, giving a more spotted appearance than ulula, in which the white typically reaches the shaft and/or the edge of the feather, giving a more barred appearance. The dark areas appear blackish-brown on caparoch compared with paler greyish-brown on ulula. Measurements of the relative depths of the pale and dark areas on the outer primaries confirm that the pale areas are consistently shallower on caparoch (pale areas c. 6 mm compared with 8–9 mm for the dark areas). There is more variation in ulula, but typically the pale areas are deeper than or equal in depth to the dark (9–10 mm compared with 8 mm or, in some cases, as little as 5 mm for the dark areas). Nominate ulula is rather variable. Paler examples are distinctive but darker birds may resemble caparoch. Among the study skins examined, the darkest specimens were immaTable I. Measurements (mm) and weights (g) of Hawk Owls Surnia ulula (from Cramp 1985 and Duncan & Duncan 1998). Comparative measurements from British specimens are as follows: Somerset in 1847, unsexed, caparoch, wing 241 mm, tail 190 mm; Shetland in 1860, unsexed, ulula, wing 235 mm, tarsus 28–29 mm; Grampian in 1898, unsexed, ulula, weight 326 g. Note that some measurements from British specimens are from the literature; the 1860 Shetland and 1898 Grampian specimens are no longer extant. S. u. ulula male female S. u. caparoch male female wing 224–239 230–249 213–245 210–242 tail 164–187 166–191 138–190 156–191 tarsus 23.9–27.0 24.4–27.2 weight 215–375 285–380 280 242–375 250–454 Paolo Viscardi © National Museum of Ireland Harrop 148. Hawk Owl Surnia ulula of the North American race S. u. caparoch, Cornwall, March 1830. ture birds. In such cases it is important to check all the characters carefully before making an identification. However, caparoch is sufficiently consistent in appearance for it to be unlikely to be confused with nominate ulula, though it is more variable in size. Ageing Ageing birds in the field is extremely difficult, though immatures in their first autumn show irregular grey-and-white V-shaped fringes along the tips of the outer primaries compared with the relatively even white arcs of adults (Cramp 1985). Measurements Measurements of specimens show much overlap between caparoch and ulula, and those of the British specimens are not in themselves sufficient to determine the taxon involved. Results of the BOURC review Acceptable records Following the review, only the four records listed below were considered acceptable. 1830, Cornwall The first British record of Hawk Owl British Birds 103 • May 2010 • 276–283 Records of Hawk Owls in Britain 1860, Shetland mentioned; remainder of front of neck and its sides mottled with white and brownish black. Upper surface Back, scapulars, and uppertail-coverts, nearly black, spotted with white, the scapulars being darkest, and those nearest the wing having numerous bar-like white marks. Wings Lesser coverts faded brownish black; greater coverts and all the quills the same, but spotted with white; the spots upon the outer webs somewhat square in form. Under surface White, barred with brownish black, the bars paler on the breast and near the tail; on each side of the breast, near the bend of the wing, a large dark patch. Tail Brownish black, the middle feathers with several narrow white bars.’ Unfortunately the specimen was destroyed by moths (Evans & Buckley 1899), but Saxby’s description of the white facial disc and white underparts with brownish-black bars that were paler on the breast and near the tail supports the identification as ulula. 1898, North-east Scotland An adult female shot at Gight on 21st November by William Smith, factor on the Haddo House Estates, was documented by Sim (1899, 1903). The account includes some measurements (weight 11.5 ounces [326 g], expanse of wings 28.5 inches [723.9 mm], length from beak to end of tail 14.5 inches [368.3 mm] but unfortunately lacks a description. The bird’s stomach was filled with bones and the hair of mice. Sim was a highly critical assessor of records; in this case, One procured from Skaw, Unst, in December 1860 by James Hay was mentioned by Crotch (1861) and described by Saxby (1874) as follows: ‘Head and neck Facial disc white, stained and slightly mottled with light dusky brown, becoming darker between the bill and the eye. Top of head and back of neck blackish brown, spotted with white, but much less on the back of the neck, where the brown lies more in patches. Outer edge of facial disc has each feather tipped with blackish brown; on each side of the neck, a long, broad, irregular line of the colour last 149. Hawk Owl Surnia ulula of the race S. u. ulula, Shetland, September 1983. British Birds 103 • May 2010 • 276–283 281 Dennis Coutts involved one taken on board a collier (coal ship) a few miles off the coast of Cornwall, in an exhausted state, in March 1830 (e.g. Proc. Zool. Soc. 1835: 77, Yarrell 1845). According to the account of the ship’s captain, Captain Stacey, the bird was so exhausted that it allowed itself to be captured by hand. The ship was bound for Co. Waterford and following its arrival the bird was kept alive. It lived for a few weeks with a friend of Dr Robert J. Burkitt’s before coming into Burkitt’s possession. Burkitt subsequently presented it to the Museum of Trinity College, Dublin, from which it passed to the National Museum of Ireland (accession number NMINH 1959.13.1). The specimen is clearly of the Nearctic race caparoch, showing relatively broad, rufous-tinged bars of consistent width on the underparts. BOURC members had some reservations about the probability of caparoch making an unassisted transatlantic crossing in light of the absence of records from the southern USA, Greenland, Iceland and the Azores, but the record’s credentials (a named finder, firsthand account, plausible date and location, and extant specimen) were sufficiently strong for the record to remain acceptable. Harrop he evidently considered the possibility both of ulula and of caparoch (then regarded as separate species) and positively identified it as ulula. The specimen is presumed to have entered a private collection but is no longer traceable. 1983, Shetland The only accepted record since the formation of BBRC involved one first seen by Angus Nicol in his garden at Frakkafield, near Lerwick, on 12th–13th September, which then moved to Bressay, where it remained on 20th–21st September (Brit. Birds 77: 538). The bird was seen by several observers and photographed. It occurred during an invasion of ulula, which brought large numbers to southern Norway and Sweden, 510 to Denmark and singles to Germany and the Faeroe Islands (Brit. Birds 77: 238, 589; Brit. Birds 78: 343). As expected, the photographs show it to be a typical example of ulula – note especially the whitish ground colour of the facial disc and underparts, and the relatively narrow blackish barring of variable width on the underparts. Records not accepted The following records were not considered acceptable, for the reasons given. 1847, Somerset This bird was said to have been shot near Yatton on 25th or 26th August at about 2.00 pm (Higgins 1851 – note that this author’s initials are E. T., not T. E. as given in error by Melling 2005). The specimen, which is mounted in a position which matches that shown in the drawing accompanying Higgins’ account, is extant at the Booth Museum, Brighton (accession number BC207261; www.virtualmuseum.info/ collections/object.asp?searchText=hawk+owl &ckid=376680&row=2&view=2). It was identified as caparoch by Dresser (1871), and the pattern of barring on the underparts of the specimen confirms this identification. The date was considered too early for natural occurrence, and the involvement of Higgins, a wealthy naturalist previously associated with the discredited taxidermist David Graham of York (Melling 2005), combined with a four-year delay between the alleged 282 date of the record and its publication, caused the Committee to doubt the validity of the record. Pre-1857, Wiltshire This bird was reportedly killed at Amesbury during severe weather by a Mr Long, though the date is uncertain, being described as ‘several years ago’ (Proc. Zool. Soc. 1876: 334), and ‘some thirty or more years since’ (Smith 1887). The specimen was exhibited at a meeting of the Zoological Society of London on 4th April 1876, and identified as nominate ulula by Bowdler Sharpe. Most contemporary and subsequent authorities either ignored or overlooked the record, which, combined with the lack of any detail about the date and circumstances of collection, made the record unacceptable. 1863 Strathclyde, 1868 Strathclyde and 1871 Strathclyde These records fall into a cluster so are treated together. The first was reportedly shot near Maryhill before 29th December 1863 (Proc. Nat. Hist. Soc. Glasgow 1: 81; Zoologist 1866: 496); the specimen may formerly have been in the Kelvingrove Museum and Art Gallery (GLAMG Z1880.122.az) but is now lost. Dresser identified it ‘at a glance’ as caparoch (Dresser 1871). The second, also listed as caparoch by Gray (1871), was reportedly shot near Greenock about ten days before 24th November 1868 (Proc. Nat. Hist. Soc. Glasgow 1: 235–236). Saunders & Clarke (1927) considered that these birds may have arrived on vessels bound for the Clyde. The last of the three records involved a specimen in very poor condition, allegedly taken near Greenock in December 1871, which had been owned by a sailor. Dresser (1871) concluded that it had been caught on board ship, and the record was considered of very doubtful authenticity by Witherby et al. (1943). The Committee was sceptical because the series of three records were from one area during a nine-year period; the first record involved a specimen which was exhibited at the same meeting as a Purple Swamp-hen Porphyrio porphyrio, reputedly from Campbeltown, Argyll; and the second and third records involved the same Greenock taxidermist. All this strongly indicated local importation and British Birds 103 • May 2010 • 276–283 Records of Hawk Owls in Britain suggested the possibility of fraudulent trade. In these circumstances, BOURC felt unable to accept any of the three. 1903, Northamptonshire This record was reported as shot at Orlingbury on 19th October (Zoologist 1904: 214) but without any supporting descriptive or other data. In these circumstances, the Committee was unable to accept the record. Other records of caparoch The only other Western Palearctic record of caparoch involves a bird from the Canary Islands in 1924. It flew onto a ship off Las Palmas and was kept alive until reaching Rotterdam harbour, before being delivered to Rotterdam Zoo on 7th November. The mounted specimen is held in the Leiden collection (RMNH/Naturalis), catalogue number 5, and has been confirmed as an immature male caparoch by Kees Roselaar. The actual date when it was first seen was not reported but it is reasonable to assume that it arrived on the ship in October. No irruptive movements were recorded in North America at that time. Although included in Martin & Lorenzo (2001), this record has not yet been reviewed by the national records committee (R. Gutierrez in litt.) and does not form part of the Spanish List (e.g. de Juana 2006). Concluding remarks This review has significantly reduced the number of accepted records, both of Hawk Owls sensu lato in Britain, and of North American caparoch in Europe. From a British point of view this species should be regarded as one of the rarest of vagrants, and each generation of observers will be lucky to get a chance of seeing one. On the basis of the accepted records, Shetland and northeast Scotland are the prime sites. It remains to be seen whether there will be any further records of caparoch; if not, the remaining accepted British record will no doubt attract further scrutiny. Acknowledgments Raymond Barlow, Wilson Hum and David Tipling provided photographs which helped to clarify differences between ulula and caparoch – some of these are reproduced above. C. S. (Kees) Roselaar kindly provided information about the 1924 Canary Islands record; Jeremy Adams helped with information about specimens in the Booth Museum, Brighton; Richard Sutcliffe helped with research into specimens held at Kelvingrove Museum and Art Galler y, Glasgow; Paolo Viscardi kindly provided information about, and images of, the 1830 specimen from Cornwall (now in Ireland). Members of BOURC commented extensively on the file during two circulations, and Bob McGowan and Tim Melling commented on and helped to improve a draft of this paper. References Alexander, W. B., & Fitter, R. S. R. 1955. American land birds in western Europe. Brit. Birds 48: 1–14. Cramp, S. (ed.). 1985. The Birds of the Western Palearctic, Vol. 4. OUP, Oxford. Crotch, W. D. 1861. Birds of Shetland. Zoologist 1861: 7706–7707. de Juana, E. 2006. Aves raras de Espana. Lynx Edicions, Barcelona. Dresser, H. E. 1871. A History of the Birds of Europe. Zoological Society of London, London. Duncan, J. R., & Duncan, P. A. 1998. Northern Hawk Owl (Surnia ulula). In: Poole, A. (ed.). The Birds of North America Online. Cornell Laboratory of Ornithology, Ithaca. Edberg, R. 1955. Invasionen av hokuggla (Surnia ulula) i Skandinavien 1950–51. Var Fagelvarld 14: 10–21. Evans, A. H., & Buckley, T. E. 1899. A Vertebrate Fauna of the Shetland Islands. David Douglas, Edinburgh. Gray, R. 1871. Birds of the West of Scotland including the Outer Hebrides. T. Murray & Son, Glasgow. Higgins, E. T. 1851. Bona fide British-killed Hawk Owl. Zoologist 1851: 3029–3032. Koopman, M. E., McDonald, D. B., Hayward, G. D., Eldegard, K., Sonerud, G. A., & Sermach, S. G. 2005. Genetic similarity among Eurasian subspecies of Boreal Owls. Aegolius funereus. J. Avian Biol. 36: 179–183. Martin, A., & Lorenzo, J. A. 2001. Aves del Archipielago Canario. Francisco Lemus Editor, La Laguna. Melling, T. 2005. The Tadcaster Rarities. Brit. Birds 98: 230–237. Saunders, H., & Clarke, W. E. 1927. Manual of British Birds. 3rd edn. Gurney & Jackson, London. Saxby, H. L. 1874. The Birds of Shetland. Maclachlan & Stewart, Edinburgh. Sim, G. 1899. European Hawk-Owl in Aberdeenshire. Ann. Scot. Nat. Hist. 1899: 49. — 1903. The Vertebrate Fauna of ‘Dee’. Wyllie, Aberdeen. Smith, A. C. 1887. The Birds of Wiltshire. Porter & Bull, London & Devizes. van den Berg, A. B., & Bosman, C. A. W. 2001. Rare birds of the Netherlands. Pica Press, Robertsbridge. Witherby, H. F., Jourdain, F. C. R., Ticehurst, N. F., & Tucker, B. W. 1943. The Handbook of British Birds. Vol. 2. H. F. & G. Witherby, London. Wood, S. 2007. The Birds of Essex. Christopher Helm, London. Yarrell, W. 1845. A History of British Birds. Vol. I. 2nd edn. Van Voorst, London. Andrew H. J. Harrop, 30 Dean Street, Oakham, Rutland LE15 6AF; e-mail [email protected] British Birds 103 • May 2010 • 276–283 283
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