Ringing & Migration Journal of the BTO Ringing Scheme

Ringing & Migration Volume 21 Part 3
Abstracts

[ For abstracts from Ringing Group Reports click here ]

Age and sex composition, biometrics, site fidelity and origin of Brambling Fringilla montifringilla wintering in Norfolk, England

STEPHEN J. BROWNE¹* and CHRIS J. MEAD²†
¹The Game Conservancy Trust, Fordingbridge, Hampshire SP6 1EF, UK
²The Nunnery, Brandon Road, Hilborough, Thetford, Norfolk IP26 5BW, UK

We analysed data collected from approximately 2,600 Brambling Fringilla montifringilla caught while attracted to artificial food at a site in Norfolk, England over seven winters. The age and sex composition of trapped birds varied between winters in relation to the total number of birds caught, but no systematic pattern was apparent. During invasion years, when a higher number of birds were present on the study site, the proportion of males was higher. In any one winter, 38-70% of the Brambling were male and 63-86% were juvenile. Very few adult females visited the study site. Males had longer wings than females, by an average of 5-6 mm and the wings of adults averaged 1-2 mm longer than juveniles. There was sexual dimorphism in body weight, with males being on average 2 g heavier than females. Adults were on average 1 g heavier than juveniles. Within winters, mean body weights were higher in warmer months. Between winters, there was significant variation in wing length and body weight, which may have been associated with variation in the geographical origin of the birds or food availability. Approximately 70% of juveniles had undergone a partial moult of the greater coverts, with an average of between 2.7 and 3.4 old greater coverts being retained. Annual variation in the progression of moult was probably due to food availability and weather conditions on the breeding grounds or where the juveniles moulted. The mean proportion of Brambling retrapped within-winters was 5.7% (range 0-15%) and there was no evidence to suggest that site fidelity was different in invasion years. Recoveries of ringed birds suggest that Brambling over-wintering in Norfolk originate from Scandinavia and pass through the Low Countries on migration.

Biometrics of nestling and adult Stonechats Saxicola torquata in southwest Ireland

SINÉAD T. CUMMINS and JOHN O’HALLORAN*
Department of Zoology, Ecology and Plant Science/Environmental Research Institute, Lee Maltings, University College Cork, Ireland

Biometric data were collected for fully-grown and nestling Stonechats Saxicola torquata in southwest Ireland. Tarsus length, wing length and mass were collected for adult and nestling Stonechats. Mean body mass of broods increased almost linearly up to eight days after hatching when it reached an asymptote prior to fledging. Mean mass growth rates of broods declined with breeding attempts and age of broods. First broods had the highest rate of increase in body mass. The mean tarsus lengths of broods differed significantly between three sites. These observed differences were not related to age or size of broods when measured. Adult body mass declined from February, prior to the start of the breeding season, to July, which coincided with the end of the breeding season. Fully-grown birds were sexually dimorphic in wing length with males having significantly longer wings than females.

Catching methods and biometrics of breeding Ring Ouzels Turdus torquatus torquatus in northeast Scotland

INNES M. W. SIM¹* and GRAHAM W. REBECCA^2
114 Craigievar Square, Edinburgh, EH12 8YP
²RSPB, 10 Albyn Terrace, Aberdeen AB10 1YP, UK

Between 1999 and 2002, we caught 116 (54 male and 62 female) breeding adult Ring Ouzels Turdus torquatus torquatus in Glen Clunie, northeast Scotland. Four different catching methods are described and their success assessed. There was no evidence that any catching method had a detrimental effect on either nest outcome, or the frequency of second breeding attempts in the same year. Plumage characteristics were used to age and sex birds caught, following their use to age and sex migrants and museum specimens. These characteristics were found to be reliable for all 19 birds of known age. Males had, on average, longer wings and deeper and whiter gorgets than females, but they were not heavier. Among both males and females 2+ year birds had, on average, longer wings than 2nd year birds, and 2+ year females were also heavier and had whiter gorgets than 2nd year birds.

Growth rates of Ring Ouzel Turdus torquatus nestlings

DAVID S. C. ARTHUR¹ and STEWART A. WHITE^2
112 Dundee Street, Carnoustie, Angus, Scotland DD7 7PD, UK
²Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Scotland G12 8QQ, UK

Breeding Ring Ouzels Turdus torquatus torquatus were studied during 1992-98 in upper Glen Esk, Angus, Scotland. Measurements of mass, wing length, tarsus length and tarsus diameter were taken from 163 nestlings of known age and graphs of these parameters plotted. Growth curves were plotted from the data and the growth constant k calculated. The growth constant for mass was greater than that for both wing and tarsus length. The calculated value of the growth constant for mass was lower than the previously published value for T t alpestris but higher than that for Blackbird T merula. Greater within-brood variability for mass was found in larger broods. There is virtually no published information on growth rates of Ring Ouzel nestlings and the data should prove a useful guide to ageing young in the nest.

Sexing Mute Swans Cygnus olor by discriminant analysis

ALLAN W. BROWN¹, LYNDESAY M. BROWN1* and PETER T. STEVICK^2
161 Watt’s Gardens, Cupar, Fife KY15 4UG, UK
²PO Box 93, Rockport, Maine 04856, USA

External measurements taken readily in the field were used to develop an alternative method of sexing Mute Swans Cygnus olor. Measurements of weight, tarsus length and skull length were taken during the period 1982 to 1999 in an area of southeast Scotland, UK. A discriminant function was developed using these biometrics to distinguish between males and females. The function derived for cygnets exceeding 7 kg in weight successfully described the sex of 88% of the original data when tested by jack-knifing. A function derived for adults correctly assigned 95% of a novel data set. Factors other than sex may influence the size of animals in a population overall, and so application of these functions to discriminate data from a wider geographical area, and when applied by other fieldworkers, should be tested prior to use.

Migration routes, breeding areas and between-winter recurrence of nominate Redwings Turdus iliacus iliacus revealed by recoveries of winter ringed birds

R. D. P. MILWRIGHT
17 Forehill, Ely, Cambridgeshire CB7 4AA, UK

Winter ringed Redwing Turdus iliacus recoveries in European/Asian wintering and breeding regions are analysed. Same-winter recoveries were on three migratory routes; a north/west continental Europe route via the North Sea coast and Maas-Seine to Atlantic France/Iberia, a south/east continental Europe route via Po-Danube to west Mediterranean, and a North Sea/British route, often via West Norway, with some birds moving on to west Iberia via a second sea crossing over the Bay of Biscay. Few same-winter recoveries moved from one route to another. Most subsequent-winter recoveries (56%) were also on the route where they were ringed (7% within 20 km of their ringing site). The majority of recoveries (59%) were in ten dense clusters with a total area of approximately 13% of suitable low-lying land in the winter range. Few birds ringed on the two continental Europe routes moved to another route in later years. Most subsequent-winter recoveries in Britain & Ireland (77%) were also originally ringed in Britain & Ireland (6% within 20 km of the ringing site), but 6% of British ringed Redwings recovered in subsequent winters were 2,500-4,000 km away in the Aegean-Caspian area. No birds ringed in Po-Danube/West Mediterranean were recovered in this eastern region. Many Fennoscandia/Baltic breeding Redwings winter in Italy/southeast France but no birds ringed in Italy/southeast France were found in this breeding region. Siberian Redwings wintering in this southern region may form the overwhelming majority of birds. Ringing in Britain & Ireland produced 59% of all recoveries in the Russian, but not Siberian, breeding region, as well as 60% of all those in the Aegean-Caspian area, suggesting that these may form parts of a the same population.

Spring arrival of passerine migrants in Iceland

HUGH BOYD*
National Wildlife Research Centre, Canadian Wildlife Service, Environment Canada, Carleton University, Ottawa, Ontario K1A 0H3, Canada

First sightings in Iceland throughout the 20th century of four summer migrant passerines were studied for possible changes in arrival dates over time, and to relate arrivals to weather conditions in Iceland and in their probable wintering and staging areas. Arrival dates advanced considerably until the 1930s, as Icelandic seasonal temperatures increased. Temperatures and arrival dates changed much less in later years, when Icelandic temperatures showed no sustained trends. Since 1950, Redwings Turdus iliacus coburni have first been seen in the last week of March, Meadow Pipits Anthus pratensis and White Wagtails Motacilla a alba about 20 April and Wheatears Oenanthe o leucorhoa about 25 April. All four species were usually seen earlier when springs in Iceland were warm and wet, and after warm winters in southern Spain. Limited records of departures in autumn suggest that the mean lengths of stay in 1951-2000 were: Redwing 233 days, Meadow Pipit 164, White Wagtail 162 and Wheatear 144 days. Sightings of Redwings and Meadow Pipits, some of which winter in Britain & Ireland, were earlier after warm winters, and during warm springs, in central England. White Wagtails and Wheatears, wintering in Africa, showed no response to English temperatures. First sightings were most likely when winds over Iceland had easterly or southerly components. In 1951-1970 arrivals of Redwings and Meadow Pipits were earlier after winters in which the North Atlantic Oscillation index had been positive and high, but before and after that period no linkage was apparent. Most of these findings resemble those reported from north Norway, though the populations of at least three of the species are probably different. They are unlike the findings from Britain and western Europe, where dates of arrival have advanced most rapidly in recent years while winter and spring warming has continued.

Temporal variation in the biometrics of Turtle Doves Streptopelia turtur caught in Britain between 1956 and 2000

STEPHEN J. BROWNE* and NICHOLAS J. AEBISCHER
The Game Conservancy Trust, Fordingbridge, Hampshire SP6 1EF, UK

We analysed biometric data collected from 589 Turtle Doves Streptopelia turtur measured between 1956 and 2000 in Britain. Male wing length was on average 4 mm longer than females, which were on average 8 mm longer than juveniles. Wing length increased by approximately 5 mm over the period 1956 to 2000, probably owing to differences in measuring techniques over the years. Males were heavier than females by about 5 g, and females were in turn 10 g heavier than juveniles. Turtle Dove body weight varied with season, with birds being heavier by about 10 g in autumn. Using the ratio of wing length to body weight to represent body condition, we found no annual variation in body condition, but body condition was lowest in spring and highest in autumn. Because we were unable to detect a change in average body condition over time, the hypothesis that lowered body condition caused reduced breeding productivity in the 1990s is unsubstantiated.

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