Ringing & Migration Journal of the BTO Ringing Scheme

Ringing & Migration Volume 21 Part 2
Abstracts

[ For abstracts from Ringing Group Reports click here ]

Seasonal movements of Fennoscandian Blackbirds Turdus merula

IAIN G. MAIN*
53 Apple Orchard, Prestbury, Cheltenham GL52 3EH, UK

Recoveries provided by 15 European ringing schemes have been used to investigate the seasonal movements of Danish, Norwegian, Swedish and Finnish Blackbirds Turdus merula. All populations are partially migratory, estimated minimum migrant fractions being 16% (Denmark), 61% (Norway), 76% (Sweden) and 89% (Finland). Britain & Ireland receive an estimated 47%, 75%, 40% and 25% of the migrants from Denmark, Norway, Sweden and Finland respectively. Most movements to Britain & Ireland from Norway, and probably from Denmark also, are directly across the North Sea. Most Swedish Blackbirds migrate through Denmark; a minority travelling through Norway in autumn may return by the majority route in spring. Most Finnish Blackbirds migrate through Sweden, with a minority crossing the Gulf of Finland to more easterly parts of Europe. Swedish and Finnish Blackbirds tend to arrive later, and to winter farther south in Britain & Ireland, than do Norwegian birds. More adult than first-year Danish Blackbirds migrate, but no other age or sex differences can be confirmed.

A preliminary comparison of population estimation by tape response and mark/recapture methods for Storm Petrels Hydrobates pelagicus in two contrasting Scottish colonies

HUGH INSLEY¹*, MICHAEL HOUNSOME², PETER MAYHEW3 and KENNA CHISHOLM^3
1 1 Drummond Place, Inverness IV2 4JT, UK
² Hooper’s Farm, Offwell, Devon EX14 9SR, UK
³ RSPB Highland Office, Etive House, Beechwood Park, Inverness IV2 3BW, UK

The tape response method of population estimation was compared to mark/recapture methods for Storm Petrels Hydrobates pelagicus on two Scottish islands. On Priest Island the du Feu single-session mark/recapture method gave an estimate not significantly different from the tape response method and was less demanding on personnel. On Eilean Hoan the Jolly-Seber estimates made in 1998 and 1999 were similar to that obtained from the tape response method in 2001. Jolly-Seber estimates made in 2000 and 2001 were similar to the du Feu estimate made in 2001, but different from the tape response method. The overall annual survival estimate of 0.87 on Eilean Hoan was identical to the previously published figure and almost the same as the 0.86 calculated from national ringing returns. These initial findings are used to identify problems with the mark/recapture methods and to suggest ways of solving them.

Bird Ringing in Britain and Ireland in 2001

Jacquie Clark, Dawn E Balmer, Sue Y Adams, Mark J Grantham, Jeremy R Blackburn, Robert A Robinson, Chris V Wernham, Bridget M Griffin and Linda J Milne
BTO, The Nunnery, Thetford, Norfolk IP24 2PU, UK

This is the 65th annual report of the British Trust for Ornithology’s Ringing Scheme covering work carried out and data received in 2001. As part of the BTO’s production of the landmark Migration Atlas: movements of the birds of Britain and Ireland, which will review movements of birds using Britain & Ireland, novel approaches to the investigation of the movement patterns and distances were developed. These allow the objective comparison of whether different species are sedentary, short-distance or long-distance migrants and the investigation of differential migration between birds of different age and sex. The BTO continues to carry out a programme of work investigating the declines of bird populations. In 2001, an investigation of Song Thrush population dynamics showed that the survival rates of young birds was key in the population decline; reduction in survival rates also seemed to have driven the fall in numbers of Marsh Tits. Work on movements of waders between roosts on the Moray Basin showed little movement for most species; important information when the possible effects of disturbance are being considered. An investigation of the biometrics of the Redshank wintering on Severn Estuary found that the proportions of Icelandic and British breeders varied between sites; again an important factor in assessing the possible consequences of disturbance. A pilot project, which is investigating the collection of data on movements and demography of farmland passerines in winter is described. Data collected as part of the Constant Effort Sites (CES) Scheme showed significant changes in the numbers of seven species between 2000 and 2001. Of these, five resident species (Blackbird, Blue Tit, Great Tit, Chaffinch and Greenfinch) and one migrant (Whitethroat) showed increases. Only one species (Willow Warbler) decreased. By contrast, productivity tended to be low with 11 species, both residents (Dunnock, Robin, Blackbird, Long-tailed Tit, Blue Tit, Greenfinch and Reed Bunting) and migrants (Sedge Warbler, Reed Warbler, Blackcap and Chiffchaff) showing significant declines. Progress on the EURO-CES project, which aims to develop standard protocols for CES fieldwork and data capture across Europe is reported. Data sets for 86 studies of 42 species were submitted as part of the Retrapping Adults for Survival (RAS) Project. The first detailed analysis of Pied Flycatcher data from RAS-type studies showed that survival rates vary between different areas of the country and confirms the value of this project. The numbers of birds ringed in 2001 (648,936) was 16% below the mean of the previous five years (1996-2000), largely as a result of Foot and Mouth Disease, which restricted the areas ringers had access to. The recovery total (10,692) was 6% lower than the five-year mean (1996-2000). Recoveries of 195 BTO-ringed birds and 77 birds ringed abroad are presented in the report and include a number of unusual or significant movements. Of particular note are the first recovery of a Great White Egret involving Britain & Ireland, the first recoveries of BTO-ringed Honey Buzzards, a BTO-ringed American Golden Plover recovered in Italy, an Hungarian-ringed Knot found in England and the first foreign-ringed Yellow-browed Warbler (from Norway) to be reported in Britain & Ireland.

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