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Ringing & Migration Journal of the BTO Ringing Scheme

Ringing & Migration Volume 21 Part 4
Abstracts

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The origin of Lesser Black-backed Gulls Larus fuscus wintering in central Iberia

ISMAEL GALVÁN¹*, JAVIER MARCHAMALO², VIDAR BAKKEN³ and JOSÉ M. TRAVERSO^4
1Área de Biología Animal, Facultad de Ciencias, Universidad de Extremadura, Avda de Elvas s/n, E-06071 Badajoz, Spain
²Picos de Urbión 57, E-28529 Rivas-Vaciamadrid, Madrid, Spain
³Zoological Museum, The Natural History Museums and Botanical Garden, University of Oslo,
PO Box 1172, Blindern, 0318 Oslo, Norway
⁴Villa de Madrid 1, E-28610 Villamanta, Madrid, Spain

The origin and age of Lesser Black-backed Gulls Larus fuscus wintering inland on the Iberian Peninsula were mapped using sightings of colour-ringed birds. A total of 288 individuals were sighted over a 17 year period. The gulls originated from seven different countries, with the majority being ringed in the United Kingdom and the Netherlands. The most commonly resighted age group were adults, and most birds were sighted two years after ringing. Our analysis provides evidence for a change in the migration patterns of Lesser Black-backed Gulls, which may be explained by Baker’s exploratory migration model. It is probable that the gulls follow the rivers Tagus and Guadiana to the rubbish tips in the inner part of the Iberian Peninsula. The prevalence of adult birds could indicate that Lesser Black-backed Gull has become established as a regular wintering species in the inner part of the Iberian Peninsula.

Habitat use, moult and biometrics in the Manchurian Reed Warbler Acrocephalus tangorum wintering in Thailand

PHILIP D. ROUND¹* and STEPHEN J. RUMSEY^2
1Department of Biology, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand ²The Wetland Trust, Elms Farm, Pett Lane, Icklesham, Winchelsea, East Sussex TN36 4AH, UK

Manchurian Reed Warblers Acrocephalus tangorum wintering at Khao Sam Roi Yot, Thailand, were largely restricted to mature Phragmites reeds. The mean wing length (± sd) of 105 Manchurian Reed Warblers was 54.5 ± 1.41 mm. There was no evidence of differences in body weight in spring, autumn or winter. Both adults and first-winter birds underwent a complete moult soon after arrival in their winter quarters. Primary moult duration was estimated to be 59 days. Moult of secondaries was suspended in approximately one-third to one-fifth of birds, the few retained, old, unmoulted feathers usually being replaced later in the winter. No further moult was usually detected prior to northward spring migration.

Bird ringing in Britain and Ireland in 2002

JACQUIE A. CLARK*, ROBERT A. ROBINSON, DAWN E. BALMER, JEREMY R. BLACKBURN, BRIDGET M. GRIFFIN, SUE Y. ADAMS, MARK P. COLLIER and MARK J. GRANTHAM
BTO, The Nunnery, Thetford, Norfolk IP24 2PU, UK

This is the 66th annual report of the British Trust for Ornithology’s Ringing Scheme covering work carried out and data received in 2002. The BTO continues to work to understand the causes of bird population declines. During the year a major report on the demography of House Sparrows† and Starlings was completed. The work showed that while the decline in House Sparrows is likely to be due to a decline in the survival rate of first-year birds, changes in productivity (the number of young birds entering the population) appear to have helped to halt the decline in recent years. For Starlings, changes in survival of first-year birds was the best way of explaining the population decline, although changes in adult survival rate may also be implicated in eastern Britain. Work on wader age ratios showed that the proportion of juvenile waders in flocks caught in winter in Britain & Ireland may provide information about breeding success of high arctic species. Such data are hard to gather on the breeding grounds because of their remoteness and the dispersed nature of the breeding birds. A novel analysis of recoveries was able to show that the origins of Willow Warblers moving through Dungeness Bird Observatory in the autumn varied through the migration period and that the patterns of movement had changed in recent years. Data from the Constant Effort Sites (CES) Scheme showed that adult abundance in 2002 was generally lower than in 2001 following poor productivity in that year. Of nine significant changes in catches of adult birds between 2001 and 2002 eight were decreases (Blackbird, Sedge Warbler, Reed Warbler, Garden Warbler, Willow Warbler, Blue Tit, Great Tit and Chaffinch), with one increase (Bullfinch). Productivity generally improved when compared to 2001 with 18 species showing a statistically significant increase between the two years (Wren, Dunnock, Robin, Blackbird, Sedge Warbler, Reed Warbler, Whitethroat, Blackcap, Chiffchaff, Willow Warbler, Long-tailed Tit, Blue Tit, Great Tit, Treecreeper, Chaffinch, Greenfinch, Bullfinch and Reed Bunting). Data sets for 110 studies of 42 species were submitted as part of the Retrapping Adults for Survival (RAS) Project. The number of birds ringed (791,074) increased, after the drop in 2001 as a result of some land access restrictions imposed due to Foot and Mouth Disease, and was 4% above the mean of the previous five years (1997-2001). The recovery total (11,042) was similar to the five-year mean (1997-2001). Recoveries of 130 BTO-ringed birds and 63 ringed abroad are presented in the report; those selected for inclusion confirm known breeding or wintering areas or migration routes and also show a number of significant or unusual movements

Biometrics, sex ratio and migration periods of Reed Buntings Emberiza schoeniclus wintering in the Tajo Basin, Spain

ALFONSO VILLARÁN1* and JUAN PASCUAL-PARRA2
1Departamento de Biología y Geología IES, Marqués de Santillana, C/ Isla del Rey, 5 28770 Colmenar Viejo, Madrid, Spain 2Avd Ramón y Cajal, 85 2A 28016 Madrid, Spain

We analysed capture and biometric data of 2,408 Reed Buntings Emberiza schoeniclus ringed at Carrizal de Villamejor, Tajo Basin, Central Spain. Reed Buntings showed a clear sexual size dimorphism; males had longer wings and were heavier than females. Body condition, as determined from the residuals of a regression of weight on wing length, was highest in males, particularly during midwinter. Mean wing length, especially of the males, decreased over the winter, probably due to feather wear and abrasion, but possibly also due to older and larger males departing earlier. Maximum mean weights were recorded in spring pre-migratory periods and minimum weights occurred in October, during the final stages of autumn migration. Female:male ratios were 3:1 in the population during winter. The ratio was at a minimum in October and at a maximum in March, which suggests that females arrived and left later than males. The earliest males arrive at Carrizal de Villamejor in autumn approximately 10 days before the earliest females, and also depart in spring 10 days sooner.

Recruitment, Site Fidelity and Dispersal of Merlins Falco columbarius from the southeast Yorkshire Dales, England

P. M. WRIGHT
32 Tarn Moor Crescent, Skipton, North Yorkshire BD23 1LT

The breeding of Merlins Falco columbarius was monitored within a study area in the Yorkshire Dales National Park over a sixteen year period. Nesting territories were visited annually to trap adult Merlins and monitor eggs and young. Standard BTO rings were used on both adults and nestlings and, in addition, passive integrated transponders (PIT) tags were fitted to adult birds, which allowed for their subsequent identification without the need to retrap. Forty-four adult Merlins and 267 nestlings were ringed or controlled at nest sites in 33 territories, for which three adult and 18 nestling recovery records were obtained. The movement of adults entering the study area to breed was predominantly from north or south, in approximately equal numbers. Many females used different territories between years, and such movements partly accounted for the high turnover of birds at particular territories. The three adult recoveries showed winter movements of 196, 264 and 287 km. The majority of recoveries of birds ringed as nestlings occurred before the end of their first calendar year, within 150 km of their natal site, and almost all to the south.

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