2008 Vol 21

Identifying giant petrels, Macronectes giganteus and M. halli, in the field and in the hand
Carlos, C. J.12*, & Voisin, J.-F.3
*Correspondence author. Email: cjcarlos@bol.com.br or macronectes1@yahoo.co.uk 1 Laboratario de Elasmobranquios e Ayes Marinhas, Departamento de Oceanografia, Fundacäo Universidade Federal do Rio Grande, CP 474, 96201-900, Rio Grande, RS, Brazil; 2 Current address: Rua Mario Damiani Panatta 680, Cinqbentenario, 95013-290, Caxias do Sul, RS, Brazil; 3 USM 305, Departement Ecologie et Gestion de la Biodiversite, Museum National d'Histoire Naturelle, CP 51, 57 rue Cuvier, F-75 005 Paris, France.
Abstract
The two similar-looking species of giant petrels, the Northern Giant Petrel Macronectes halli and the Southern Giant Petrel M. giganteus, are renowned for being difficult to identify. In this paper we review and offer new guidelines on identification of these birds at sea, on land, and as dead specimens. Criteria for identifying giant petrels are available in the scientific literature, especially regarding bill-tip coloration which readily differ from one species to another. Plumage characters, although useful to discriminate species, are not adequately covered at present. Thus, for each species we describe in detail and illustrate distinctive age-related plumage stages, or types, from juveniles through to adult breeders.We also comment on giant petrel biometrics, body weight, and some aspects of their behaviour, in order to help ornithologists and birdwatchers separate males and females, and eventually specimens from South America—Gough Island, Antarctic and sub-Antarctic regions.

2008 Vol 21

Vagrancy of Brunnich's Guillemot Uria lomvia in Europe
Van Bemmelen, R.1*, & Wielstra, B.2
*Correspondence author. Email: rvanbemmelen@gmail.nl
1 Stavangerweg 535, 1013 AX Amsterdam, The Netherlands; 2 Dr. Benthemstraat 10-91, 7514 CM Enschede, The Netherlands.
Abstract
We review the occurrence of vagrant Brunnich's Guillemots Uria lomvia in Europe. The 104 records of 109 individual birds that could be traced showed a distinct seasonal pattern. There were no September records, but a small autumn peak was apparent in late October and early November. Numbers increased again in early December, peaked in late January and early February, and declined through spring, with only seven records in summer. Autumn records were mostly of first-winter birds, whereas relatively more adults were recorded in winter, in line with expectations based on timing of migration for these different age classes. We speculate that vagrant birds to western Europe have strayed from the wintering grounds and migration routes south of Iceland and along the Norwegian coast, while overland movements from the Barents Sea may explain inland records from northern Scandinavia, and some from the Baltic Sea. Two spatial clusters of records were evident, one in Scotland and the other in the Skagerrak, Kattegat and southern Baltic Sea. Between 1975/76 and 2005/06, the number of records declined in the former region but increased in the latter, which may represent a real decrease in occurrence, and increased observer effort, respectively.

2008 Vol 21

A survey of Leach's Oceanodroma leucorhoa and European Storm-petrel Hydrobates pelagicus populations on North Rona and Sula Sgeir, Western Isles, Scotland
Murray, S.1*, Money, S.2, Griffin, A.3 & Mitchell, P. l.4
*Correspondence author. Email: murraysurvey@yahoo.co.uk
1 Craigie Dhu, Cardney, Dunkeld, Perthshire PH8 OEY, UK; 2 Rain tree House, Church Lane, Drayton St Leonard, Oxfordshire OX10 7AU, UK; 3 15 Horologie Hill, Arbroath, Angus DD 11 SAE, UK; 4 Joint Nature Conservation Committee, Dunnet House, 7 Thistle Place, Aberdeen A810 1 UZ, UK.
Abstract
Leach's Storm-petrel Oceanodroma leucorhoa was first recorded breeding on North Rona in 1883 and on Sula Sgeir in 1939. European Storm-petrel Hydrobates pelagicus was first recorded on North Rona in 1885 and on Sula Sgeir in 1958. Since then, there have been attempts to estimate the population size of both species on North Rona but there is little information about their current status on Sula Sgeir. In 2001, systematic surveys of both species using tape playback were conducted for the first time on both islands. North Rona held 1,133 Apparently Occupied Sites (AOS) of Leach's Storm- petrel but only 371 AOS of European Storm-petrel; numbers on Sula Sgeir were five and eight AOS respectively. The combined population of both North Rona and Sula Sgeir of Leach's Storm-petrel and European Storm-petrel, comprise 2.3% and 1.4% respectively, of the total number of each species breeding in Great Britain.

2008 Vol 21

The diet of European Shag Phalacrocorax aristotelis, Black-legged Kittiwake Rissa tridactyla and Common Guillemot Uria aalge on Canna during the chick-rearing period 1981-2007
Swann, R. L.1*, Harris, M. P.2 & Aiton, D. G.3
*Correspondence author. Email: robert.swann@homecall.co.uk
1 14 St Vincent Road, Tain, Ross-shire IV19 1JR, UK; 2 Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BY, UK (current address: CEH Bush Estate, Penicuik, Midlothian EH26 OQB, UK); 3 14 Buckstone Howe, Edinburgh EH 10 6XF, UK.
Abstract
Chick diet of European Shags Phalacrocorax aristotelis, Black-legged Kittiwakes Rissa tridactyla and Common Guillemots Uria aalge at Canna was investigated over a 27- year period. The diet was mainly composed of Sprats Sprattus sprattus, Lesser Sandeels Ammodytes marinus and members of the Gadidae (a variety of species but mainly Trisopterus spp. and Whiting Merlangius merlangus). Other groups (ten families of fish, crustaceans, cephalopod molluscs and polychaete worms) were of minimal importance. Lesser Sandeels dominated the diet of young Black-legged Kittiwakes and European Shags, Sprats the diet of young Common Guillemots, whereas gadid otoliths were by far the commonest items found in pellets regurgitated by older European Shags. There were few significant temporal changes in species composition or the size of prey taken over the 27 years and the results confirm earlier findings that gadids are a normal and important part of the diet of seabirds at this colony.

2008 Vol 21

Colony habitat selection by Little Terns Sternula albifrons in East Anglia: implications for coastal management
Ratcliffe, N.1*, Schmitt, S.2, Mayo, A.2, Tratalos, J.3 and Drewitt, A.4
*Correspondence author. Email: notc@bas.ac.uk
1 RSPB, East Scotland Regional Office, 10 Albyn Terrace, Aberdeen AB 10 1 YP, UK (Current address: British Antarctic Survey, NERC, High Cross, Cambridge C83 OET, UK); 2 RSPB, The Lodge, Sandy, Bedfordshire SG19 2DL, UK; 3 University of East Anglia, Norwich NR4 7TJ, UK; 4 English Nature, Northminster House, Peterborough PE7 1 UA, UK.
Abstract
Little Terns Sternula albifrons are unusual among UK seabirds in that a large proportion of the population breed on mainland beaches in East Anglia. Relative sea-level rise means that such habitats are under threat in this region, and so we quantified colony habitat selection of beach nesting Little Terns in order to inform habitat restoration and creation initiatives. Random 1 km sections of beach were selected and the presence or absence of a Little Tern colony within each was related to physical (substrate type, height and width), biotic (vegetation cover, predator activity) and anthropogenic (disturbance) characteristics using logistic regression models. Little Terns positively selected for beaches with vegetation cover and negatively for those with high disturbance levels. They showed no selection according to width and height or Red Fox Vulpes vulpes presence, even though these are likely to affect flood and predation risk respectively. Red Foxes were found to be widespread on beaches irrespective of tern colony presence, and so movement of tern colonies will not always result in predator avoidance. Little Tern habitat creation needs to be integrated into coastal management plans in order to safeguard their population from the combined threats of relative sea-level rise, predation and disturbance.

2008 Vol 21

Descriptive anatomy of the subcutaneous air diverticula in the Northern Gannet Morus bassanus
Daoust, P.-Y.1*, Dobbin, G. V.1, Ridlington Abbott, R. C. F.2 & Dawson, S. D.3
*Correspondence author. Email: daoust@upei.ca
1 Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE ClA 4P3, Canada (Current address for G. V D: Department of Laboratory Medicine, Queen Elizabeth Hospital, P.O. Box 6600, Charlottetown, PE CIA 8T5, Canada); 2 Class of 2005, Department of Biology, Faculty of Science, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE CIA 4P3, Canada (Current address: 772 Osborne Street, Summerside, PE C1N 4N5, Canada); 3 Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE CIA 4P3, Canada.
Abstract
Northern Gannets Morus bassanus typically forage by diving from high above the water surface. Their subcutaneous (s-c) tissues are invested by an elaborate system of air diverticula that presumably function in cushioning the impact of their entry into the water. The anatomical details of this system were studied by dissection and latex injection in 15 carcasses of these birds. The s-c air diverticula consist mainly of two independent systems of intercommunicating compartments that are bilaterally symmetrical, cover the ventral and lateral regions of the trunk and the proximal portions of the wings and legs, and communicate with the ipsilateral region of the clavicular respiratory air sac. This communication, which opens into the axillary region, is through a narrow gap between the subcoracoideus and coracobrachialis caudalis muscles. Two other, smaller, independent systems of s-c air diverticula, also bilaterally symmetrical, may contribute to cushioning the Northern Gannet's body during its dives: one at the thoracic inlet, which communicates with the corresponding side of the clavicular air sac, and the other along the neck, which communicates with the nasal cavities and the choanal opening. Further work is required to define more precisely the function of these extensive air diverticula and air circulation within them.

2008 Vol 21

Population decline of Leach's Storm-petrel Oceanodroma leucorhoa within the largest colony in Britain and Ireland
Newson, S. E.1*, Mitchell, P. 1.2, Parsons, M.2, O'Brien, S. H.2, Austin, G. E.1, Benn 5.3, Black J.4, Blackburn, J.1, Brodie, B.3, Humphreys, E.5, Leech, D.1, Prior, M.6 &Webster, M.7
*Correspondence author. Email: stuart.newson@bto.org
1 British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK; 2 Joint Nature Conservation Committee, Dunnet House, 7 Thistle Place, Aberdeen AB10 1UZ, UK; 3 19 Culloden Court, Inverness IV2 7DX, UK; 4 3 Newgate Street, Bingham, Nottingham NG13 8FD, UK; 5 BTO Scotland, School of Biological and Environmental Sciences, Cottrell Building, University of Stirling FK9 4LA, UK; 6 1 Rother Close, Greenmeadow, Swindon, Wiltshire SN25 3PZ, UK; 7 16 Grice Close, Sheringham, Norfolk NR26 8UG, UK.
Abstract
This study used diurnal playback of vocalisations to examine the abundance of breeding Leach's Storm-petrel Oceanodroma leucorhoa on Dun, St Kilda in 2003 and 2006 in relation to the only previous survey conducted using similar methodology in 1999. The number of Apparently Occupied Sites in 2006 was 12,770, not significantly different to the 14,490 found in 2003, but significantly lower than the 27,811 found in 1999, by 54%. The magnitude and rate of the decline are of major conservation concern. Great Skua Stercorarius skua predation is thought the most likely cause but other factors such as poor food supply cannot be ruled out. The importance of continued monitoring of Leach's Storm-petrel and Great Skua is discussed.