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Ringing
& Migration
Journal of the BTO Ringing Scheme |
Ringing & Migration Volume 20 Part
4
Abstracts
[ For abstracts from Ringing Group
Reports click here ]
Notch factor - a technique for separating
Marsh Warblers Acrocephalus palustris from Reed Warblers A.
scirpaceus on spring migration
DAVID KELLY1*, NIGEL CLEERE2
and Prof CHARLES W. T. PILCHER3
1Elms Farm, Icklesham, East Sussex TN36 4AH, UK
237 Beechcroft, Hampstead, Norreys, Berkshire RG18 0TG, UK
3Department of Pharmacology, Faculty of Medicine, PO Box 24923,
Safat, Kuwait
Using measurements which are regularly collected on Reed Acrocephalus scirpaceus
and Marsh Warblers Acrocephalus palustris, a new method was tested which
appears to give better separation than the currently available biometric
techniques. The length of the notch on the inner web of the second primary
is multiplied by the number of the primary whose tip it falls adjacent to
(numbering ascendently) to calculate the 'notch factor'. This factor successfully
separated (on biometrics alone) 1,574 out of 1,577 birds trapped in the
spring migration through Kuwait. Reed Warblers trapped represented individuals
from both the scirpaceus and fuscus races.
Site fidelity and recurrence of some migrant
bird species in The Gambia
J. MICHAEL B. KING1* and
JOHN M. C. HUTCHINSON2
1Stonehaven, 16 Marsh Road, Frome, Bath, Somerset
BA11 6PE, UK
2Max-Planck-Institut für Bildungsforschung, Lentzeallee
94, D-14195 Berlin, Germany
Regular ringing was carried out over most of five winters at Ginak in The
Gambia. We analyse retrap data from 12 species of migrant birds to examine
whether they remain for more than one day within a winter, and whether they
return to the study area in subsequent winters. We investigate both the
rate of recurrence (between-winter retraps within the whole area, approximately
1,000m across) and site fidelity (tendency to be retrapped within 100m of
first capture). Some adjustment of recurrence for annual survival is attempted.
For individuals trapped at least twice over a winter, we tabulate the interval
between first and last capture: in all 12 species this was over six weeks
for some individuals; furthermore, site fidelity within a winter is demonstrated
in most species retrapped in reasonable numbers, exceptions were Garden
Warbler Sylvia borin and Blackcap Sylvia atricapilla. Most species recurred
at appreciable rates in successive seasons, and in three species with a
sufficient sample size, Subalpine Warbler Sylvia cantillans, Whitethroat
Sylvia communis, and less certainly Olivaceous Warbler Hippolais pallida,
the evidence was of site fidelity between winters. We compare recurrence
rates with data collected at Djoudj in north Senegal.
Biometrics of adult Grey Plovers Pluvialis
squatarola breeding in the Lena Delta, NE-Siberia (The Sakha Republic,
Yakutia)
KLAUS-MICHAEL EX01* and
OLGA STEPANOVA2
1Institut für Vogelforschung "Vogelwarte
Helgoland", An der Vogelwarte 21, 26386 Wilhelmshaven, Germany
2117 420 nl, Nunet Kina 29-227, Moscow, Russia
The Grey Plover Pluvialis squatarola is a circumpolar breeding wader
with slight clinal but discontinuous morphometric variations in the Palearctic.
Birds breeding in eastern Siberia seem to be larger than birds breeding
in western Siberia as well as those breeding in northern Canada and Alaska.
Biometric data on 15 Grey Plovers trapped in the Lena Delta 1997 are supplied.
In all morphometrical measurements females were on average larger than males,
and significant differences occurred for tarsus length (48.1 vs 45.9mm).
Furthermore, during incubation females were significantly heavier than males
(228.9 vs 217.7g). Sexes could be distinguished by discriminant functions.
Most measurements support the view that Palearctic birds are larger than
Nearctic ones, but differentiation within the Palearctic remains obscure.
Wing, tarsus and bill length of the Lena birds correspond with data from
western Siberian birds rather than from eastern Siberia/Alaska; bill length
coincides with measurements from Wrangel Island. Besides sex-specific and
geographical differences, migration routes and location of overwintering
areas are discussed.
Redwing Turdus iliacus migration in
Italy: an analysis of ringing recoveries
ALESSANDRO ANDREOTTI*, LIONELLO BENDINI,
DARIO PIACENTINI and FERNANDO SPINA
Istituto Nazionale per la Fauna Selvatica, Via Cà Fornacetta
9, 40064 Ozzano Emilia (BO), Italy
Redwing Turdus iliacus migration in Italy has been investigated on
the basis of ringing recoveries stored at the Italian Ringing Scheme. A
total of 718 foreign recoveries and 936 recoveries of birds ringed in Italy
have been analysed. Most Redwings migrating through, and wintering in, Italy
come from the Baltic area. The first thrushes on post-nuptial movements
arrive in September, though the bulk of movements starts in the second week
of October, peaking in mid-November and ending in late November, while Italy
seems not to be influenced by strong return movements. In regions of northern
Italy like Lombardia very few birds stay after December, while good numbers
of wintering Redwings are reported from areas with a milder climate like
Toscana. The previously reported low fidelity to the wintering grounds is
confirmed by our analysis, suggesting the use of two distinct areas in subsequent
years; the potential influence on the selection of wintering quarters of
local conditions upon departure for the Baltic crossing is discussed.
Effects of handling stress on Brunnich's Guillemots
Uria lomvia
LINDA J. WILSON1* and ANTHONY
J. GASTON2
1Department of Biology, University of York, York
YO10 5DD, UK
2Canadian Wildlife Service, National Wildlife Research Centre,
100 Gamelin Blvd, Hull, Quebec K1A 0H3, Canada
The effects of various handling procedures on breeding Brunnich's Guillemot
Uria lomvia were compared, using the length of time it took for individuals
to return to the colony after handling (return time), to indicate the degree
of stress imposed. Return times were affected by sex, with males taking
longer to return than females. There was no significant effect of experience
(age), although experienced males (>7 years old, the largest sample group)
tended to have shorter return times than inexperienced males. Only experienced
males were used to compare the effects of treatment on return times. Treatments
included attachment of depth gauges, blood sampling, and two control groups
of birds held for 10 and 20 minutes. Return times did not differ significantly
among treatments, except for the group that was held for 20 minutes. Return
times were significantly correlated with handling times. We conclude that,
for experienced male Brunnich's Guillemots, the type of treatment used did
not have any significant effect over and above that imposed by the amount
of time the bird was held. The results suggest that treatment during handling
may not be an important factor determining stress, compared to the effect
of capture and the subsequent amount of time spent in captivity.
Biometrics of the Twite Carduelis flavirostris
HUGH CLARK1 and ROBIN M.
SELLERS2
13 Lindsay Place, Wick, Caithness KW1 4PF, UK
2Crag House, Ellerslie Park, Gosforth, Cumbria CA20 1BL, UK
This paper presents a summary of information on the biometrics of the Twite
Carduelis flavirostris based on measurements of live birds captured
during the winter months in Caithness, weights of birds caught on Fair Isle,
North Ronaldsay, Spurn Point and Oronsay, and wing and tail lengths of skins
of birds collected in Britain, Ireland and Scandinavia. A significant sexual
dimorphism was found in wing and tail lengths, with males being the larger
sex, but not in tarsus or bill length; no significant age-related differences
were found. Scandinavian birds (C. f. flavirostris) had significantly longer
wings and tails than British or Irish birds (C. f. pipilans). There was
also significant variation in these two parameters within Britain &
Ireland and a significant trend of both mean wing and tail length with latitude
and longitude. It is concluded that there is a roughly south-west to north-east
cline in body size within the western European population of the Twite.
Birds wintering in Caithness increased weight progressively more or less
throughout the hours of daylight at rates of 0.15g h-1 in females and 0.21g
h-1 in males. Weights also increased steadily from October to December,
changes which were largely parallelled by increases in fat. Females reached
their maximum weights during the breeding season whilst males reached a
maximum around the beginning of moult in July. Lowest weights occurred in
late winter and around the end of moult. The weights of birds caught on
migration were similar to those of birds trapped in mid-winter and it is
estimated that such birds maintained around 1g fat, sufficient to enable
the birds to fly c. 300km in still air, which is at the upper end of the
range of distances Twites typically move in Britain.
The status of Icelandic Redshank Tringa
totanus robusta in north Kent during autumn
K. DERRETT1 and R. SMITH2*
114 Chestnut Avenue, Staplehurst, Kent TN12 0SA, UK
267 York Avenue, Chatham, Kent ME5 9ES, UK
Two races of Redshank occur in the British Isles, the nominate race Tringa
totanus totanus which breeds in Britain and mainland Europe, and the
Icelandic race T.t.robusta which breeds only in Iceland and the Faeroes.
Birds from Iceland are generally larger than the nominate race. This paper
quantifies the proportion of Icelandic birds present in north Kent in autumn
by analysing biometric data using the Summers et al. (1988) calculation
for the determination of population composition within mixed flocks of Redshank.
To assist in this analysis a comparison is made between birds caught in
Moray Firth, Scotland and The Swale, north Kent. Redshank of the Icelandic
race Tringa totanus robusta form an insignificant proportion of the
population of Redshank to be found in north Kent in autumn.
Migration of four Sylvia warblers through northern
Senegal
ULF OTTOSSON1*, STEPHEN RUMSEY2
and CHRISTIAN HJORT3
1Department of Animal Ecology, Ecology Building, SE-223 62 Lund,
Sweden
2The Wetland Trust, Elms Farm, Pett Lane, Icklesham, Winchelsea,
East Sussex TN36 4AH, UK
3Hessle, Munkarp, SE-243 91 Höör, Sweden
We present ringing data from the Parc National des Oiseaux du Djoudj, Senegal,
for Blackcap Sylvia atricapilla, Orphean Warbler S. hortensis,
Subalpine Warbler S. cantillans and Whitethroat S. communis.
A total of 5,607 birds of the four species were ringed during 1987-1996
and, of these, 951 were retrapped. We discuss the migratory strategies of
the different species in relation to their pre-migratory fuel-deposition
and how far they can fly theoretically with the recorded fat contents. Most
birds carry enough fat at take off to take them at least to Morocco, probably
Iberia and, with tailwinds, possibly even further north.
A method for ageing adult Corncrakes Crex
crex
RHYS E. GREEN1, NORBERT SCHÄFFER2
and DIETER WEND3
1Royal Society for the Protection of Birds and Conservation Biology
Group, Department of Zoology, University of Cambridge, Downing Street,
Cambridge CB2 3EJ, UK
2Royal Society for the Protection of Birds, The Lodge, Sandy,
Bedfordshire SG19 2DL, UK
3Seitenstr 2, 04838 Mörtitz, Germany
The shapes of the tips of Corncrake Crex crex secondary remiges grown by
chicks and adults were compared. Measurements of secondaries of birds of
known age were obtained from wild Corncrakes in Britain and captive-bred
birds originating from Germany and Poland. The tips of secondaries grown
in the hatching year were more pointed than those grown in subsequent years
in both samples. Secondaries grown in the hatching year are retained until
the autumn of the next calendar year. Consequently the average shape of
the tips of secondaries of one year old adults was different from that of
older birds. The sum of the angles measured at the tips of secondaries 3
to 6 inclusive (numbered ascendantly) was used to quantify this difference.
The angle sum scores of known first-years and older birds overlapped, but
it is possible to estimate the proportions of the two age classes in a sample
of adults of unknown age by assuming that the distribution of scores is
the combination of two normal distributions with means and standard deviations
taken from the reference samples of known-age birds. The method can also
be used to assign individual adults to these two age classes, but if the
proportion of errors is kept to less than 1% then it is necessary to leave
the 35% of birds which have intermediate scores unaged.
Migration patterns and sex ratios of diving
ducks wintering in Northern Ireland with specific reference to Lough Neagh
DARREN M. EVANS* and KEITH R. DAY
School of Biological and Environmental Sciences, University of Ulster,
Coleraine, Co. Londonderry BT52 1SA, UK
Several duck species exhibit differential migration, whereby females settle
further south than males on the winter grounds after the autumn migration.
This is most exaggerated in the diving ducks. In Northern Ireland generally,
the migration patterns of Common Pochard Aythya ferina, Tufted Duck A. fuligula,
Greater Scaup A. marila, and Common Goldeneye Bucephala clangula are similar
to those observed in Great Britain. On Lough Neagh in particular, the sex
ratios of wintering flocks of diving ducks were observed between the winters
of 1996 and 1999. On average, 79% of Common Pochard, 72% of Tufted Duck
and 66% of Common Goldeneye wintering on Lough Neagh were male. The possible
reasons for differential migration of the sexes include body size dimorphism
resulting in different cold temperature tolerances, advantages for males
in returning to breeding grounds sooner and intersexual competition excluding
the less competitive females to areas further south.
Biometrics and sex ratios of Skylarks Alauda
arvensis during migration in southern Italy
SERGIO SCEBBA*
Gruppo Inanellamento Limicoli (GIL, Naples), Traversa Napoli 58, 80078
Pozzuoli, Naples, Italy
Biometric data (wing, third primary, tail and tarsus length) were collected
from 3,034 Skylarks Alauda arvensis on autumn migration in 1998 and
1999 at Ischitella (Caserta), along the southern Tyrrhenian coastline. There
was a clear bimodality in wing, third primary and tail lengths due to sexual
size dimorphism. The distributions of biometrics were used with Harding-Cassie
plots to separate males from females. On this basis, over the two-year study,
between 47.7% (1999) and 56.3% (1998) of birds caught at Ischitella were
females and between 31.8% (1998) and 40.7% (1999) were males. The remaining
11.6 to 11.9% had intermediate values of wing, tail and primary length and
were not sexed. These sex ratios were very different from those estimated
for north European populations, where males predominated in catches.
Evening mist-net closure: implications for
data collection and bird welfare
A. SORACE1 *, M. GUSTIN1,2
and G. LANDUCCI1
1SROPU c/o Via R.Crippa 60 D/8, 00125 Roma (Acilia), Italy
2LIPU (Lega Italiana Protezione Uccelli), Via Trento 49, 43100
- Parma, Italy
Wild birds captured with mist-nets for study purposes should be released
and returned to the wild as soon as possible to reduce the stress of being
handled. Studies of migratory birds involving mist-netting for 24h/day may
result in diurnal birds being caught late in the day and kept overnight.
This may be particularly detrimental to migrants stressed by migratory flight
and to sedentary birds during reproduction. The closure of mist-nets in
the evening may avoid these problems, but is believed to severely reduce
the amount of data collected. In this study we show that the evening closure
of mist-nets does not translate into a significant reduction in captures
of migrants because the number of migrants captured in the evening is low,
and the reopening of mist-nests before sunrise does not reduce the captures
in the following diurnal hours. The evening closure of mist-nets reduced
disturbance because it avoided keeping both nocturnal migrants (including
those which were about to leave the study area) and sedentary birds overnight.
Therefore, mist-nets may be closed in the evening without jeopardising the
success of a study. The loss of data caused by the evening closure of mist-nets
may however be significant for the few species with partially or completely
crepuscular activity such as the Nightingale, Luscinia megarynchos.
The impact of trapping and handling activities
on the breeding performance of Hooded Crows Corvus corone cornix
HENRIK OLSEN* and NIELS MARTIN SCHMIDT
Department of Ecology, Zoology Section,
The Royal Veterinary and Agricultural University, Thorvaldsensvej 40,
DK-1871 Frederiksberg C, Denmark
Trapping of Hooded Crows Corvus corone cornix has been conducted
for decades in an attempt to regulate population size. However, the effect
of trapping activity on the breeding performance of crows is more or less
unknown. In this study, trapping activities, involving Larsen-traps and
decoy birds, were conducted at 14 Hooded Crow nest sites. Trapping was successful
at eight nests, and a total of 12 individuals were caught. Hooded Crow breeding
ceased within a few days following the trapping sessions and the territories
were abandoned. This also happened at nests without trapping success, suggesting
that the trapping activity itself, and not the actual trapping and handling
of the birds, caused the cessation of breeding. The very high density of
crow nests in the study area and the associated high risk of conspecific
predation on the eggs is suggested as the most likely explanation for the
observed effect on Hooded Crow breeding performance.
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