Wilson's Storm-Petrel with White Stripes on the Underwing

Notes

Wilson’s Storm-petrel with white stripes on the underwing European Storm-petrel Hydrobates pelagicus 2007), and a Wilson’s with such underwing is separated from Wilson’s Storm-petrel stripes could be mistaken for a European. Oceanites oceanicus by several key features This note documents three cases of this with (flight behaviour, structure, plumage) but photographs: 4th March 2005, off Cape Horn, field guides typically emphasise its white Chile; 12th March 2006, at sea, off South underwing-covert panels. These are formed Georgia; 14th August 2008, at sea, off the Isles by white greater coverts and primary median of Scilly (plates 138–140). Plates 138 & 139 coverts, and the longest axillaries, which are show stripes formed by white median under- dark with white tips (there is some variation). wing-coverts. The underwing stripes visible in These white feathers stand out from the rest plate 140 are in the region of the median of the dark brownish-black underwing, giving underwing-coverts and may result from narrow white panels. The panels are eye- missing feathers or white in the feathers. catching, even at long range, though less The origins of these birds is unknown. obvious with wear. In contrast, the underwing They may be rare variants from Atlantic popu- of Wilson’s is typically brownish-black with lations or come from Chilean populations. median and greater coverts faintly paler. White in the underwing is a characteristic of However, in the Atlantic, Wilson’s Storm- Wilson’s that breed in Chilean fjords and these petrel can (rarely) show white underwing smaller birds are recognised by some authori- stripes across the coverts (Flood & Thomas ties as a distinct taxon, Fuegian (Wilson’s) Storm-petrel O. o. chilensis. Their non- breeding range is unknown. The status of Oceanites storm-petrels off Chile is currently under review following the discovery of a distinct population (in terms of both plumage and biometrics), perhaps a new species (following Dowdall et al. 2009); this has white in the underwings, but populations are thought to be localised. Elliot’s Storm-petrel O. gracilis also has white in the underwings, and on the vent, but breeds much farther north in the Pacific and is extremely unlikely to find its way Richard White Richard 138. Wilson’s Storm-petrel Oceanites oceanicus, to the Atlantic. The taxon O. o. magallenicus off Cape Horn, Chile, 4th March 2005. from the Falklands and Tierra del Fuego, no Brent Brent Stephenson Marc Guyt 139. Wilson’s Storm-petrel Oceanites 140. Wilson’s Storm-petrel Oceanites oceanicus, oceanicus, off South Georgia, 12th March 2006. off the Isles of Scilly, 14th August 2008.

272 © British Birds 104 • May 2011 • 272–277 Notes longer recognised, may be linked to O. o. O’Keeffe, M. 2009. Unidentified storm-petrels off chilensis and might warrant reinvestigation. Puerto Montt, Chile, in February 2009. Dutch Birding 31: 218–222. Flood, R. L., & Thomas, B. 2007. Identification of ‘black- References and-white’ storm-petrels of the North Atlantic. Dowdall, J., Enright, S., Fahy, K., Gilligan, J., Lillie, G., & Brit. Birds 100: 407–442. Robert L. Flood, 14 Ennor Close, Old Town, St Mary’s, Isles of Scilly TR21 0NL; e-mail [email protected]

Spring feeding assemblies of the Hobby in Britain The Hobby Falco subbuteo arrives in southern the first week of May. Most of the sites consist Britain from its African winter quarters from of open water (notably flooded gravel-pits or mid April onwards but the nesting period is peat workings) and/or reedbeds, with a few from early June. During the pre-breeding wet grasslands and lowland mires. period, Hobbies gather in flocks of varying Peak counts during the years 2001–10 for size to feed on concentrations of insects, pre- a selection of the larger sites are given in table dominantly over wetlands. On the basis of a 1. No trend is evident except for Shapwick literature review and consultation with local Heath and Lakenheath Fen, where numbers observers, we tried to quantify the location, have increased steadily. size and timing of these assemblies, and to identify the chief prey items of the falcons. To what extent do these gatherings The most recent year for which data were involve immature Hobbies? available for all counties of England and It is often difficult to identify first-summer Wales was 2007. In that year at least 30 sites birds in flight, particularly at a distance or in in southern England and the Midlands had unfavourable light, but the regular observa- five or more Hobbies at any one time during tions of NPW at Shapwick Heath suggest that the pre-breeding period. The sites are, with first-summers probably form less than 5% of one exception (Whixall Moss, Shropshire), to the total present. It also appears that they the south of a line between the Severn and generally arrive later than adults and some- the Wash. Three (Shapwick Heath in Som- times remain after the main assembly of erset, Lakenheath Fen in Suffolk and Stod- adults has dispersed. marsh in Kent) had exceptional numbers, not matched at other locations in Britain. Do they comprise local birds, passage Peak numbers of Hobbies at all sites migrants or a mixture? occurred between 24th April and 14th June, During the breeding season, the Hobby’s with the majority in the last week of April and feeding range has been estimated to be chiefly

Table 1. Peak counts of Hobbies Falco subbuteo at key sites for pre-breeding gatherings in Britain, 2001–10. 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 mean Fen Drayton Lakes, Cambridgeshire 8 14 18 20 16 16 16 20 14 19 16 Marston Vale Pits, Bedfordshire n/r 10 n/r 756816 n/r 21 7 Shapwick Heath, Somerset 12 30 40 43 56 41 52 47 68 84 47 Lakenheath Fen, Suffolk 12 12 19 36 35 37 27 32 40 65 31 North Warren, Suffolk 6762612 9 20 18 12 10 Woolhampton GP, Berkshire n/r 423710 17 20 10 8 9 Moatlands/Theale, Berkshire 7 11 6 13 6811 5 16 10 9 Amwell NR, Hertfordshire 59412 10 9514 6 13 9 Stodmarsh, Kent 29 27 52 70 38 20 28 36 39 35 37 Wilstone Reservoir, Hertfordshire 8 11 7718 6612 6 13 9 Dungeness, Kent 16 15 15 24 10 10 88715 13 Whixall Moss, Shropshire 10 18 5257524 1 14 9 Totals 113 168 174 239 212 182 192 254 225 309 n/r = not recorded

British Birds 104 • May 2011 • 272–277 273 Notes

within 2–3 km of the nest-site, sometimes up (Trichoptera) and mayflies (Ephemeroptera). to 6 km (Chapman 1999). Given known Observers have noted Libellula species, partic- nesting densities, it is unlikely that the larger ularly Four-spotted Chaser, damselflies and St feeding assemblies comprise only local terri- Mark’s Fly swarming at high density during tory holders. Observations of aerial courtship this period, thereby providing an abundant at these gatherings suggest that some birds are food source for the Hobbies. already paired, although this could represent Termites (Termitoidae) are believed to be pairs migrating together. The fact that peak a major component of the Hobby’s diet in its numbers are concentrated in late April/early African wintering quarters and clearly the May suggests that some passage migrants are species is exploiting another rich insect involved and we believe that these are more resource in lowland wetlands on arrival in prevalent, at least at the major feeding sites. Britain. Common Swifts Apus apus and hirundines are often seen feeding in close What is their main food resource? proximity to the Hobbies at these concentra- A number of insect species or families were tions of aerial insects but are typically identified as prey items from the reports sum- ignored by the falcons. marised here: dragonfly spp., notably Four- Acknowledgments spotted Chaser Libellula quadrimaculata and We thank Ian Dawson, RSPB Librarian, the County Hairy Dragonfly Brachytron pratense; damselfly Recorders and other observers for providing data for spp., notably Common Blue Enallagma this study. cyathigerum, Azure Coenagrion puella and Reference Large Red Pyrrhosoma nymphula; St Mark’s Fly Chapman, A, 1999. The Hobby. Arlequin Press, Bibio marci; Alder Fly Sialis lutaria; caddisflies Chelmsford. Anthony Chapman, 17 Lambert Close, Framlingham, Suffolk IP13 9TE; e-mail [email protected] Nick P. Williams, The Falcons, Cadeleigh, Tiverton, Devon EX16 8HW; e-mail [email protected]

White-winged Black Terns in Poland in 2010 – a record breeding season In 2010, record numbers of nesting White- (many flocks of 1,000–2,000 individuals) was winged Black Terns Chlidonias leucopterus apparent and, in June and July, it was clear were noted in Poland. In May, a strong passage that huge numbers had stayed to breed. In all, a total of 11,860–12,242 nesting pairs, in c. 167 colonies, was recorded. Most birds (92%) were found in large river valleys in eastern Poland and major breeding sites were in the Narew (4,135–4,235 pairs, 33 colonies), Biebrza (4,080 pairs, 51 colonies) and Bug river valleys (1,770–1,940 pairs, 31 colonies). In the west (to the west of the Vistula River), Łukasz Zandecki 141. White-winged Black Terns Chlidonias leucopterus in the Narew River 956–1,021 pairs in c. 32 valley near Grady Woniecko, northeast Poland. In 2010, the Narew River colonies were found, valley was the most important breeding site for this species in Poland. mainly in the valleys of

274 British Birds 104 • May 2011 • 272–277 Notes the Warta (437–452 pairs), Bzura (165 pairs) and Notec rivers (95–105 pairs). Over 95% of colonies were in river valleys, flooded meadows and oxbow lakes. The mean number of pairs per colony was 73; most birds (44% of the total) were found in medium- sized colonies of 11–50 pairs, with smaller

numbers in colonies of Łukasz Zandecki 51–100 pairs (27%), 142. White-winged Black Terns Chlidonias leucopterus in the Biebrza River 100+ pairs (15%) and valley near Mscichy, northeast Poland. The main breeding site of this tern 1–10 pairs (14%). The in the Biebrza River valley was in the Mscichy neighbourhood in 2010. largest colonies, in the Narew, Biebrza and Bug 2009/10 in Poland contributed to spring valleys, comprised 300–700 pairs. White- floods in many areas, and water levels winged Black Terns nested in single-species remained high throughout the whole of the (53% of pairs) as well as in mixed-species subsequent breeding season. colonies (47%), the latter alongside Black In Poland, nesting White-winged Black Terns C. niger (52%), Whiskered Terns C. Terns occur mainly in the east-central low- hybrida (26%), Black-headed Gulls Chroico- lands; the species breeds annually only in the cephalus ridibundus (15%) and Common Biebrza Marshlands and is otherwise only a Terns Sterna hirundo (7%). sporadic breeder. In Europe as a whole, In Poland, the sporadic peaks in the where the breeding population is estimated number of nesting White-winged Black Terns at 74,000–210,000 pairs (BirdLife Interna- in some years (fig. 1) probably reflect unusu- tional 2004), the species occurs mainly in ally dry conditions on the main European east-central areas, with the highest numbers breeding grounds (in Ukraine, Belarus and in Russia, Ukraine, Belarus, Azerbaijan, parts of neighbouring Russia) together with Poland and Hungary; it also breeds irregu- the occurrence of more suitably damp habi- larly in the Apennine Peninsula, the Balkans tats along river valleys in Poland, as in 2010 and Germany. In 2010, approximately 8% of (Tomiałoj & van der 13,000 Winden 1997; Grüneberg 12,051 & Boschert 2009). In 12,000 2007, for example, the relatively high number 5,000 of White-winged Black 4,000 Terns breeding in Poland and Germany was prob- 3,000 ably due to drought conditions in Ukraine from 2,000 March to May, while water levels remained 1,000 high through to late 0 spring in Poland and 85 87 89 91 93 95 97 99 01 03 05 07 09 Germany (Grüneberg & Fig. 1. The breeding population (pairs) of White-winged Black Terns Boschert 2009). The cold Chlidonias leucopterus in Poland, 1985–2009 (data source: Polish Rarities and snowy winter of Committee).

British Birds 104 • May 2011 • 272–277 275 Notes the European population nested in Poland Weißflügelseeschwalben in Deutschland: and there were also record numbers in Bestandsentwicklung und aktuelle Brutverbreitung. DDA-Monitoring-Rundbrief 1: 9–13. (In German) Germany, with 410–470 pairs in the eastern Sellin, D., & Schirmeister, B. In press. Erneut große part of the country (Peene River valley; Sellin Brutansiedlung der Weißflügel-Seeschwalbe & Schirmeister in press). Chlidonias leucopterus im Peenetalmoor bei Anklam (Mecklenburg-Vorpommern). Ornithologische Mitteilungen 63. (In German) References Tomiałoj, L., & van der Winden, J. 1997. White-winged BirdLife International. 2004. Birds in Europe: population Black Tern Chlidonias leucopterus. In: Hagemeijer, W. J. estimates, trends and conservation status. BirdLife M. & Blair, M. J. (eds.), The EBCC Atlas of European International, Cambridge. Breeding Birds, pp. 366–367. Poyser, London. Grüneberg, C., & Boschert, M. 2009. Weißbart- und Łukasz Ławicki, West-Pomeranian Nature Society, Flisacza 35e/6, 74-100 Gryfino, Poland; e-mail [email protected]

Green Woodpecker excavating a cavity in autumn On 20th–24th September 2010, at Normafa, buildings are also sometimes occupied in the Buda Hills, Hungary, I observed an (BWP). There is, however, no mention in the adult male Green Woodpecker Picus viridis literature of Green Woodpeckers creating excavating a cavity. The bird made an entirely holes specifically for roosting, though they new hole in a large Beech Fagus sylvatica tree have been recorded adapting existing holes and I was able to watch it at length on several for this purpose in autumn (Blume 1996). occasions. It was clear that the bird was not Although I have observed a Black Wood- foraging; it simply hacked chips of wood pecker excavating a cavity in autumn from the hole and flicked them away. On (Gorman 2010), I have previously never September 23rd, I watched the bird entering observed a Green Woodpecker doing so the cavity just before dusk, where it remained outside the breeding season or for use specif- as darkness fell – clearly the cavity had been ically as a roost site. created for use as a night roost. Green Woodpeckers will excavate cavities References in spring, usually March–April, for use as Blume, D. 1996. Schwarzspecht, Grünspecht, Grauspecht nesting sites, though they also regularly reuse [Black Woodpecker, Green Woodpecker, Grey- headed Woodpecker]. Die Neue Brehm-Bucherei. existing cavities for that purpose. Some of Spektrum Akademisscher Verlag, Heidelberg. these holes, the holes of Black Woodpeckers (In German) Dryocopus martius, nestboxes and natural Gorman, G. 2010. Black Woodpecker excavating a cavity in autumn. Brit. Birds 103: 411. tree cavities are also used as roosts. Holes in

Gerard Gorman, Budapest 1511, Pf:4, Hungary; e-mail [email protected]

Exceptional numbers of Redwings roosting in Hampshire

During early November 2009, unusually large tinued to monitor the roost from the Sloden numbers of Redwings Turdus iliacus were side and on 17th had around 12,000 flying in. noted in various parts of the New Forest, Two further observers were recruited to Hampshire. The New Forest Winter Bird attempt a co-ordinated count on 22nd, which Survey, over the weekend of 7th–8th produced a total of 28,250. From later discus- November, produced a total of 7,428 at 35 sion, it was clear that some birds had been sites, including at least 2,000 seen by Martin ignored by all of us, while potential flight Bennett flying over Sloden Inclosure to roost lines of birds flying into the roost from the in thicket-stage Douglas Firs Pseudotsuga south had not been covered. The next day, menziesii in Broomy Inclosure. On 9th MB recorded at least 25,000 flying into November, MB returned to the area and Broomy Inclosure, from the south over High counted at least 4,410 flying to roost. He con- Corner Wood, and on 26th November he

276 British Birds 104 • May 2011 • 272–277 Notes counted 18,350 following the same flight line. comparable figures were 30 out of 81 A further co-ordinated roost count, with (37.0%) and 35 out of 149 (23.5%) respec- more observers involved, was arranged for tively (Wernham et al. 2002). 28th November. This produced a total of What attracted so many Redwings to the 10,885, and although birds were no doubt New Forest? One experienced keeper said the missed owing to the heavy rain and poor visi- numbers were far higher than he’d ever seen. bility, it was clear that a lot of Redwings had There was certainly a massive Holly Ilex left. Subsequent counts were lower still, with aquifolium berry crop, which proved attrac- the New Forest Winter Bird Survey on 12th/ tive, and the birds were also taking advantage 13th December producing only 413 at 23 of damp conditions in the woodlands by sites. feeding on the ground. Reasons for the It seems that numbers in the roost peaked abrupt departure are a mystery – the Holly around 22nd–23rd November. Making crop had certainly been depleted to some allowance for birds missed on 22nd and extent but plenty of berries remained on the adding in MB’s count of birds arriving from bushes at the time of the second co-ordinated the south on 23rd, the roost is estimated at count. 60,000 birds. The previous highest roost In November 2010, none was found at count on record for Hampshire is 2,000 Broomy Inclosure, but a roost was located 5 (Clark & Eyre 1993). A search of bird reports km to the ENE in young Corsican Pines and avifauna for 25 English counties revealed Pinus nigra in Long Beech Inclosure. Co- only seven counts in excess of 5,000: in ordinated counts on 23rd and 25th Devon, up to 40,000 at Thornham Cross November produced totals of 15,185 and between November 1994 and January 1995 15,060 respectively. (Grant and Smallshire 1995, Tyler 2010); in Somerset, up to 30,000 at Berrow Hill in Acknowledgments Thanks to Martin Bennett for drawing attention to the March 1969, up to 21,000 at Rowberrow large numbers of Redwings present in November 2009 Warren in the winters of 1960/61 and and monitoring the area on an almost daily basis 1961/62, 10,000 at Mansmead Wood in Feb- throughout the period, Keith Betton for organisation of ruary 1980 and the same number at Stock the New Forest Winter Bird Surveys, Andrew Page for locating the 2010 roost and providing information Hill in January 1991 (Ballance 2006); and in about the trees in the roost areas, and to all the West Midlands, 8,000 at Brandon in late observers who helped in the co-ordinated counts in March 1977 (Harrison 1982). BWP offers both years. little information on the subject and records a maximum roost of 1,200. Following the References Winter Atlas in 1981–84, the British and Irish Ballance, D. K. 2006. A History of the Birds of Somerset. Isabelline Books, Penryn. wintering population was estimated to be of Brown, A., & Grice, P. 2005. Birds in England. Poyser, the order of 1 million birds (Lack 1986), London. while Brown & Grice (2005), using the same Clark, J. M., & Eyre, J. A. (eds.) 1993. Birds of Hampshire. source, suggested a total of 750,000 for Hampshire Ornithological Society, Over Wallop. Grant, K. R., & Smallshire, D. (eds.) 1995. Devon Bird England, with most of these south of a line Report 1994. Devon Birdwatching and Preservation between the Mersey and Thames Estuaries. Society, Exeter. Thus a roost of 60,000 is nationally impor- Harrison, G. R. (ed.) 1982. Birds of the West Midlands. West Midland Bird Club, Studley. tant, although numbers in autumn may be Lack, P. C. 1986. The Atlas of Wintering Birds in Britain higher than in midwinter as ringing data and Ireland. Poyser, Calton. show that many move on to winter in France Tyler, M. W. 2010. The Birds of Devon. Devon or Iberia. Of birds ringed in Britain in Birdwatching and Preservation Society, Exeter. Wernham, C. V., Toms, M. P., Marchant, J. H., Clark, J. A., October and November and recovered in the Siriwardena, G. M., & Baillie, S. R. (eds.) 2002. The same winter, 173 out of 227 (76.2%) had Migration Atlas: movements of the birds of Britain and moved further than 20 km, whereas Ireland. Poyser, London. in December and January/February the John M. Clark, 4 Cygnet Court, Old Cove Road, Fleet, Hampshire GU51 2RL; e-mail [email protected]

British Birds 104 • May 2011 • 272–277 277