Ringing & Migration Journal of the BTO Ringing Scheme

Ringing & Migration Volume 22 Part 1
Abstracts

[ For abstracts from Ringing Group Reports click here ]

Sexing juvenile Greenfinches Carduelis chloris by the extent of black on the tail

MARTA ARENAS¹* and JUAN CARLOS SENAR^2
1Departamento de Bioloxía Animal, Universidade de Santiago, Campus Sur, E-15782, Spain
²Museu Ciències Naturals, P° Picasso s/n, 08003 Barcelona, Spain

There is increasing interest in the study of the evolution of sex ratios in birds. Correct assignment of sex to fledgling and juvenile birds is critical for studies that deal with differential sex allocation at nests or sexual variation in survival or dispersion rates. Here we describe a non-intrusive method based on plumage colouration by which juvenile and fully developed nestling greenfinches can be sexed reliably. By measuring the length of the black area on the fifth tail feather rachis, we were able to sex 100% of birds reliably; males had lengths less than 31.44 mm, whereas females were longer. The Greenfinch may, therefore, be a valuable species for the study of sex ratio variation.

The utility of national ring recoveries for identifying the effects of an exceptional mortality event amongst seabirds

STEPHEN J. BROWNE¹, JACQUIE A. CLARK* and WILL J. PEACH²
British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK

Ring recovery data were used to describe a seabird mortality event (or ‘wreck’) affecting mainly Shags Phalacrocorax aristotelis and Guillemots Uria aalge in the North Sea during February and March 1994. Stormy weather and onshore winds are thought to have caused this mortality. Most Shags and Guillemots were recovered along the North Sea coast of the British Isles, particularly around northeast Britain. In non-wreck years, recoveries of Shags and Guillemots were more widespread around the British Isles. Most Shags recovered during the wreck originated from North Sea breeding colonies in northeast England, eastern Scotland and the Northern Isles, while most Guillemots originated from colonies in eastern Scotland and the Northern Isles. In contrast to previous wrecks, the 1994 wreck affected mainly adult Shags and first- and second-year Guillemots. The national ring recoveries confirmed the extensive scale differences in mortality between species and age classes that were previously evident from an intensive study on the Isle of May.

Sexing and ageing Rose-ringed Parakeets Psittacula krameri in Britain

CHRISTOPHER J. BUTLER¹ and ANDREW GOSLER
Edward Grey Institute for Field Ornithology, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK

Although Rose-ringed Parakeets Psittacula krameri over three years old can easily be sexed due to the males’ rose-coloured neck-rings and black bibs, sexually immature males and females are considered impossible to separate in the hand. The biometrics of males and females overlap but males tend to be slightly larger than females in all measurements. We derived a discriminant function to separate the two sexes using wing length, bill length and the number of fully yellow underwing coverts. Biometrics were recorded for 235 individuals captured between February 2001 and May 2003. Feather and blood samples were taken from 45 of these birds to determine the sex by haplotyping. The measurements from these known-sex individuals (22 females and 23 males) were pooled with the measurements for adult males and a binary logistic regression function was derived which correctly separated 96.6% of the known sexes. The first data on moult patterns in Britain were obtained and are useful in ageing birds during the spring. In addition, it was found that the tips of primaries were rounder in adult birds than in juveniles, a result that agrees with other studies on parrots and some other bird species.

Ringing recoveries confirm higher wader mortality in severe winters

JACQUIE A. CLARK
British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK
and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK

Periods of severe weather can result in significant mortality in bird populations. In Britain there is a system of voluntary, followed by official, bans on wildfowl hunting in coastal areas during periods of severely cold weather, in order to minimise disturbance to bird populations during these periods of energetic stress. The effectiveness of such hunting bans will be influenced by the spatial variation in severe weather and consequent mortality. Reports of dead ringed birds (recoveries) clearly show that the number of recoveries of waders increases in severe weather periods. The distribution of this mortality in severe weather varies between species and both temporally and spatially. It is suggested that the numbers of recoveries received in severely cold weather could be monitored and used to confirm that increased mortality is occurring.

Migration and morphometrics of Temminck’s Stint Calidris temminckii at Ottenby, southern Sweden

ANDERS HEDENSTRÖM*
Department of Theoretical Ecology, Ecology Building, SE-223 62 Lund, Sweden

Data are reported from 55 years of ringing and observation on the migration of Temminck’s Stint Calidris temminckii at Ottenby Bird Observatory, Sweden. Numbers ringed have declined since the 1940s due to high numbers caught in 1948 and 1949. Thereafter there is no clear trend. The overall autumn migration direction of 13 recoveries is south-southwest, with a concentration of recoveries in northeast Italy. Median date of spring passage was 20 May, while median date of autumn passage was 28 July for adults and 20 August for juveniles. Hence, the duration of the breeding season is about two months. On autumn migration, adults carry larger fuel (fat) loads (32% of lean body mass, LBM) than juveniles (21.2%), and so adults are capable of a direct flight to the northeast Italian stopover, while the average juvenile cannot do so unless assisted by winds. Over the autumn migration season, fuel loads did not change in adults but late migrant juveniles had higher fuel loads. The maximum rate of fuel accumulation was 7.7% of LBM, which is near the physiological maximum. The maximum migration speed was estimated to be 150 km/day.

Autumn migration of thrushes over eastern Finland: a comparison of visible migration and ringing recovery patterns

MARKKU J. HUTTUNEN
Department of Biology, University of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland

The migration of thrushes Turdus spp over eastern Finland was investigated using data from 4,482 foreign recoveries of five species ringed in Finland between 1913 and 2001, and records of visible migration of nearly 28,000 thrushes observed during diurnal autumn movements between 1996 and 2001. Ringing recoveries suggested that the main autumn direction of movement from eastern Finland is southwest for Redwings T iliacus, Fieldfares T pilaris and Song Thrushes T philomelos, west-southwest for Blackbirds T merula and south for Mistle Thrushes T viscivorus. Visible migration records for Mistle Thrushes seemed to correspond well with ringing recoveries, but the other thrush species showed different directions of movement, mainly towards the west-northwest or along a west-northwest to east-southeast axis, possibly due to the influence of lake districts as guidelines. The available wind data showed that the thrushes flew in an inappropriate west-northwest direction on most peak movement days regardless of wind direction, though some correspondence with moderately strong head or cross winds was evident. The majority of foreign recoveries of thrushes ringed in Finland were found between western and southern Europe but a small proportion of birds have also been recovered from southeast and northwest sectors. The rather irregular migratory behaviour of Redwings and Fieldfares is exemplified by the ringing recoveries of individual birds, or birds from the same brood, in entirely different areas during subsequent winters. This might be explained by drift during migration, movements during hard weather or intense nomadic behaviour.

The removal of colour rings by Greenfinches Carduelis chloris

ZIEMOWIT KOSINSKI
Institute of Environmental Biology, Department of Avian Biology and Ecology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland

This paper examines the effect of sex and ring colour on the frequency of removal of plastic colour rings by Greenfinches Carduelis chloris. Of 55 recaptures of 42 individuals, 22 (40%) had lost at least one of its colour rings. Females showed a tendency to remove colour rings more frequently than males. For both sexes, there was a similar tendency to remove more dark than light-coloured rings. While it is not possible to identify a specific reason why the birds remove their colour rings, it is possible that discomfort on the nest may play a role in ring removal by females and, more speculatively, it is possible that males might remove colour rings to manipulate their sexual attractiveness to females. Wrap-around rings might provide a solution to the problem of colour-ringing species with powerful beaks.

Fat and pectoral muscle in migrating Sedge Warblers Acrocephalus schoenobaenus

CHRIS P.F. REDFERN¹*, VICKY J. TOPP² and PHIL JONES^3
1Medical Molecular Biology Group, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK ²School of Marine Sciences and Technology, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK ³Elms Farm, Pett Lane, Icklesham, Winchelsea, East Sussex TN36 4AH, UK

Increases in fat and pectoral muscle mass are important physiological changes associated with migration, but the extent to which these are linked is uncertain. The relationship between fat and pectoral muscle in first-year Sedge Warblers Acrocephalus schoenobaenus was investigated using the carcasses of 20 birds that died by flying into the lighthouse on Bardsey Island, North Wales, UK, in autumn 1996, and data for fat and pectoral muscle scores from 3,281 Sedge Warblers ringed while on migration through the Wetland Trust Reserve at Elms Farm, Sussex, UK, between the end of July and early October in the years 2000, 2001 and 2002. For the Bardsey sample, the mass of tracheal pit fat (claviculo-coracoid fat body) correlated with the masses of fat at other body sites, and was a good measure of overall fat levels. Lean dry pectoral muscle mass did not correlate with the mass of tracheal pit fat, suggesting that pectoral muscle mass and fat mass are independent measures of body size. The link between fat and pectoral muscle mass was investigated further using the Elms Farm data. Wing length, time of capture, fat score and pectoral muscle score all made significant contributions to overall body mass. Although fat and pectoral muscle scores were correlated overall, analysis by year and fat score range supported the idea that these can vary independently. Analysis of fat and pectoral muscle scores by different ringers suggested that fat scores were consistently applied in different years; however, pectoral muscle scores may be harder to standardise between ringers. In summary, we suggest that fat and pectoral muscle mass increase independently in preparation for migration, but the factors which determine variation in pectoral muscle scores in relation to fat scores in different years are unknown.

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