Ringing & Migration Journal of the BTO Ringing Scheme

Ringing & Migration Volume 22 Part 4
Abstracts

[ For abstracts from Ringing Group Reports click here ]

Sexing Starlings Sturnus vulgaris using iris colour

E.L. SMITH, I.C.CUTHILL, R. GRIFFITHS2, V.J. GREENWOOD1, A.R. GOLDSMITH and
J.E. EVANS
1Centre for Behavioural Biology, School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK 2Molecular Laboratory, DEEB, Graham Kerr Building, Glasgow University, University Avenue, Glasgow G12 8QQ, UK

We took blood samples from 100 post-fledging juvenile Starlings Sturnus vulgaris for DNA sexing in late August, and scored the traits that are commonly thought to predict sex in adults: iris colour, length and shape of the throat feathers, degree of speckling of plumage, body mass and tarsus length. Using logistic regression, the iris colour alone predicted the sex, as determined from the DNA, with 97% accuracy. By using iris colour and the length of the throat feathers together, 98% of birds were sexed accurately and greater separation of groups was achieved. These features were still reliable in the following February, when the birds had come into breeding plumage. At this stage, the colour of the base of the bill was 100% accurate in predicting sex.

The decline of the Ring Ouzel Turdus torquatus in Britain: evidence from bird observatory data

I. J. BURFIELD1 and M. DE L. BROOKE*
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK

Analysis of British and Irish bird observatory data from 1970-1998 shows that the number of Ring Ouzel Turdus torquatus bird days has declined significantly in spring at western observatories through which British-breeding birds pass, but not at east coast observatories through which Fennoscandian breeders pass. The extent of decline corresponds roughly to the decline in numbers of British breeders as assessed on the breeding grounds. While these results could indicate that the decline in British Ring Ouzels is caused by problems on the breeding grounds, we also highlight the possibility that differences in the timing and routing of British and Fennoscandian birds when migrating across continental Europe could expose the former to greater risks from hunting.

Ages of Storm Petrels Hydrobates pelagicus prospecting potential breeding colonies

J. DAVID OKILL and MARK BOLTON
1Heilinabretta, Trondra, Shetland ZE1 0XL, UK 2RSPB, UK Headquarters, The Lodge, Sandy, Bedfordshire SG19 2DL, UK

Each year, ringers using sound lures mark and recapture immature Storm Petrels Hydrobates pelagicus prospecting potential breeding colonies. Attempts have been made to estimate the size of this population, but a full demographic model has not been possible since the age structure of this population has not been determined. To address this, between 1990 and 2004, 799 Storm Petrel chicks were ringed at the breeding colony on the Island of Mousa, Shetland, to establish a sample of marked known-age birds. There were 39 subsequent recaptures of these individuals, mainly by using sound lures at sites away from breeding colonies. Only one recapture related to a first-year bird: the largest cohort was of second-year birds and the relative frequencies of third-year and fourth-year cohorts progressively diminished as birds entered the breeding population and ceased responding to sound lures. These data provide demographic information to facilitate the construction of population models. Given the difficulty in determining the size of breeding populations of Storm Petrels and in long-term annual monitoring of breeding productivity, there may be considerable conservation benefit from ringing and recapture of Storm Petrels each year to monitor the size of the pre-breeding population.

Bird ringing in Britain and Ireland in 2004

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

This is the 68th annual report of the British Trust for Ornithology’s Ringing Scheme, covering work carried out, and data received, in 2004. During the year, changes in bird survival in relation to winter weather were studied. In almost all cases, there was a greater influence of weather on first-year than adult survival. A paper providing guidelines to help those setting up demographic monitoring schemes for waders was produced, with ringing as a key component. Concern about a reduction in reporting rates of ringed birds led to a study of the changes. Declines were found across nearly all taxonomic groups and may reflect a combination of changes in reporting behaviour, ringing behaviour or bird behaviour. A study of the timing of muirburning used the ringing dates of pulli in conjunction with nest record data to assess its possible effect on breeding birds. There appears to be little reason for differences in cut-off dates for muirburning in different regions and at different altitudes, but further work is required to quantify more fully the effects on moorland birds. Data gathered as part of the Constant Effort Sites (CES) Scheme showed increases in the numbers of adults of several, mainly migrant, species, possibly as a result of high rainfall in Africa south of the Sahara. Productivity was good for most species. Cetti’s Warbler Cettia cetti was added to the list of species covered and a study of habitat on CE sites showed that vegetation management mitigates the effect of habitat progression on catching rates. Data for 117 Retrapping Adults for Survival (RAS) studies were submitted. Over 12,000 Swallows Hirundo rustica were ringed as part of the Swallow Roost Project. The total number of birds ringed (881,920) was the highest ever, showing an 18% increase on the mean of the previous five years (1999-2003). The recovery total (11,930) also increased (by 9% compared to the mean of the previous five years). Recoveries of 154 BTO-ringed birds and 102 ringed abroad are presented in the report. They include records that confirm suspected or known migration patterns as well as the more unexpected movements.

Back to Index of Issues