Ringing & Migration Journal of the BTO Ringing Scheme

Ringing & Migration Volume 25 Part 1
Abstracts

The White-throated Dipper Cinclus cinclus subspecies in Spain

FRANCISCO CAMPOS, M. ÁNGELES HERNÁNDEZ, JUAN ARIZAGA, TOMÁS SANTAMARÍA and LUIS CORRALES

Based on variations in breast plumage colour, two subspecies of White-throated Dipper Cinclus cinclus have been acknowledged to exist in Spain: C. c. cinclus in northwestern and central regions, and C. c. aquaticus in the eastern and southern regions. Within the White-throated Dipper’s Spanish range, 37 rivers were sampled between 2000 and 2007. Dippers with a brownish-red and dark brown breast plumage were both present within the same large areas and rivers. Moreover, because plumage colour changes individually with age, no clear-cut geographical distribution pattern was found. These observations suggest that breast colour cannot be used to distinguish White-throated Dipper subspecies in Spain.

Patterns of migration and wintering of Robins Erithacus rubecula in northern Iberia

JJUAN ARIZAGA, DANIEL ALONSO and EMILIO BARBA

The aim of this study was to analyse the patterns of migration and wintering of European Robins Erithacus rubecula in northern Iberia (Plaiaundi Ecological Park, Irún, N Spain). Overall, 185 Robins were ringed at weekly trapping sessions from September 2004 to April 2005. The temporal distribution of abundance and recaptures indicated that the autumn migration period lasted from September to November, the winter period from November to February, and the spring migration from March to April. Some wintering Robins arrived earlier than most of the migrants which passed through the area in autumn, whilst most left the area before the majority of spring migrants appeared. First-winter Robins were always more abundant than older birds, and females more abundant than males. Morphological traits varied only in relation to sex, and it was not possible to distinguish between migrating and wintering Robins from measurements. Overall, body mass and fuel load were low during both the autumn and spring migrations, supporting the idea that Robins passing through northern Iberia migrated in short steps. In winter, however, higher values of body mass (but not of fat scores) were observed.

The movement patterns of two populations of Twites Carduelis flavirostris in Ireland

DEREK McLOUGHLIN, CHRIS BENSON, BRYONY WILLIAMS and DON COTTON

The Twite Carduelis flavirostris is one of only three passerines included on the red list of Birds of Conservation Concern in Ireland. As part of a study on its ecology, we investigated the local movement patterns of two populations of Twites in Counties Mayo and Donegal between January 2006 and July 2008. The breeding populations studied comprised over 40 of an estimated 54–110 breeding pairs in Ireland. Colour ringing was used to identify individual Twites in the field. In the course of this study, 492 birds were ringed, of which 480 were caught outside the breeding season; 57 (12%) were resighted on their breeding grounds. The breeding birds spent most of the winter season within 28 km of their breeding areas. We also describe the size and structure of the home ranges of 11 Twites radio tracked over four periods – March, May, June and August – on the Mullet Peninsula, County Mayo, in the northwest of Ireland. The results of this study suggest that Irish Twites are mainly sedentary and that their populations appear to be augmented by Scottish breeding birds during the winter months.

Migrating passerines can lose more body mass reversibly than previously thought

VOLKER SALEWSKI, MARC HERREMANS and FELIX LIECHTI

Knowing the amount of body mass that migrants can lose is essential for the estimation of potential flight ranges, assessing the importance of stopover sites or modelling migration strategies. ‘Lean’ body mass, (the mass without fat stores) is often used to describe the limit of body-mass loss but birds also use protein as fuel for flight. The mean body mass of 621 passerines mist-netted in Mauritania between 2001 and 2004 with a fat score of 0 (no visible subcutaneous fat stores) and a muscle score of 0 (emaciated flight muscle) was much lower compared to the lean body mass values found in the literature. Recaptures showed that these birds were able to refuel again. The mean body mass of 122 Garden Warbler Sylvia borin with both a fat score and a muscle score of 0 was 12.8 g. The mean potential flight range of four Garden Warblers captured in the desert was 35% higher when 12.8 g was used for the estimation compared to the 15.0 g often used in previous studies. This has implications for future studies of the migration strategies of passerines, and suggests that, in the past, the fuel load of migrating passerines has been underestimated.

Analysis of biometric data to determine the sex of Woodpigeons Columba palumbus

DAIRE Ó HUALLACHÁIN and JAMES DUNNE

Sexual dimorphism is slight in Woodpigeons Columba palumbus. Although it is generally believed that males are somewhat larger than females, there is considerable overlap between the sexes. Recent studies have highlighted the use of discriminant function analysis in determining the sex of sexually monomorphic birds such as seabirds. This study examines whether discriminant analyses can be used to determine the sex of Woodpigeons. Analysis of 298 adult Woodpigeons showed significant differences in some morphological features of male and female birds. The measurement of the variables tail and tibio-tarsus demonstrated that 66% of the entire data set could be accurately sexed. When results were examined on a seasonal basis, spring results (using wing and tibio-tarsus) were most accurate, correctly sexing 90% of females and 86% of males. Winter samples, using weight and tail measurements, were the least accurate, correctly identifying 57% of females and 65% of males.

Brood-patch development and female body mass in passerines

CHRIS P.F. REDFERN

The brood patch in passerine birds is an area of thickened and vascularised skin which develops to facilitate incubation. In the British Trust for Ornithology Ringing Scheme, the stage of brood-patch development is recorded using a six-point scale. Since eggs represent a substantial proportion of adult body mass, the body mass of females may vary as a result of ovarian growth, egg laying and incubation. The aim of this study was to test the hypothesis that the body mass of females varies in relation to brood-patch stage, using ringing data collected at a single site in the UK during the breeding season. The data analysed were for females of four species of summer migrants and six resident species. Data for a migrant species in which the males also incubate and develop brood patches were also analysed to compare males and females at equivalent stages. In eight of the 10 species studied, female body mass was highest at a brood-patch score equivalent to a pre-incubation stage. There was a clear seasonal decline in female body mass for birds with fully developed or regressing brood patches. Comparisons of standardised body mass between species suggests that brood-patch data could be used to measure annual and regional variation in breeding phenology.

Can Iberian Water Rail Rallus aquaticus be sexed reliably using simple morphometrics?

BENITO FUERTES, JAVIER GARCÍA, JUAN FERNÁNDEZ, SUSANA SUÁREZ-SEOANE and JUAN JOSÉ ARRANZ

In this paper we classified the sex of 39 Iberian Water Rails Rallus aquaticus using external morphometric measurements and genetic analysis. Logistic regression and classification tree model techniques (CART) were used to test whether simple morphometric measurements alone could classify sex correctly. For most of these measurements the overlap between sexes was too great to be of value. Bill length was the most relevant variable according to all the statistical analyses for the population under study. The applied combination of statistical techniques on biometric and genetic data correctly classify 80% of individuals. However, in view of the apparent variability in morphometric characteristics between populations, morphometric techniques to sex individuals from other populations should be validated using other criteria.

Use of external biometrics to sex Carrion Crow Corvus corone, Rook C. frugilegus and Western Jackdaw C. monedula in Northern England

KATHY FLETCHER and ROBIN FOSTER

Carrion Crow Corvus corone, Rook C. frugilegus and Western Jackdaw C. monedula culled as part of a predator control study in Northern England were sexed by inspecting internal reproductive organs and measured to determine whether external biometrics (wing, head-plus-bill and tarsus length) could be used to identify the sex of live birds. Tarsus length was found to vary between observers measuring the same bird so was not considered further. Due to considerable size overlap between the sexes it was not possible to sex all individuals correctly, particularly those less than a year old. The larger males and smaller females could be sexed with 85–93% accuracy, in adult birds using wing length of Carrion Crows of male >327 mm, female <309 mm; Rook male >320mm, female <307 mm; and Western Jackdaw male >246 mm, female <233 mm. Head-plus-bill length improved the number of birds sexed when used in combination with wing length for Carrion Crow and Rook.

Predominantly northward dispersal of Grey Herons Ardea cinerea from a heronry in Greater Manchester, UK

STEPHEN E. CHRISTMAS, WESLEY J. HALTON, KANE BRIDES and STUART P. SHAR

In 1988 a ringing study was commenced with the aim of determining patterns of dispersal from a large heronry in Greater Manchester, north-west England. Between 1988 and 2008, over 900 nestling Grey Herons Ardea cinerea were ringed at the heronry, rings from 53 of which were subsequently recovered. The overall annual recovery rate was 5.7% but this declined significantly from 7.5% between 1988 and 1996 to 3.8% between 1997 and 2007. Around 60% of ring recoveries were within the first year of the bird’s life. There was a statistically significant bias in dispersal direction towards the north-east, with a number of birds being reported in midwinter up to 100 km to the north-east. This predominantly north-eastward dispersal may have been associated with a range extension in that direction, facilitated by a succession of milder winters.

SHORT REPORTS

Age determination of Corn Buntings Emberiza calandra by skull ossification after the autumn moult

NADJA WEISSHAUPT and ANTONIO VILCHES-MORALES

Garden Warbler Sylvia borin migration in sub-Saharan West Africa

NICHOLAS J. BAYLY and STEPHEN J.R. RUMSEY

Satellite tracking of a Booted Eagle Aquila pennata during migration

DAMIEN CHEVALLIER, FRÉDÉRIC JIGUET, THÉRÈSE NORE, FRANÇOIS BAILLON and PASCAL CAVALLIN

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