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Migration, wintering and longevity of birds ringed at Falsterbo (1947-1980)

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... The reed warbler winters in tropical West Africa (Moreau 1972, Zink 1973) and migrates at night towards S and SW in autumn (cf. Roos 1984Roos , A , kesson et al. 1996b. Every autumn approximately 2000 reed warblers are captured at Falsterbo Bird Observatory (55°23%N, 12°50%E). ...
... The expected forward migratory direction towards southwest (cf. Roos 1984Roos , A , kesson et al. 1996b) was calculated based on the mean flight departure direction (a= 201°, range: 180°-245°, r=0.97, N=17, P B 0.001, Rayleigh test). ...
... The great majority of the reed warblers departed on nocturnal migratory flights towards south of southwest, which corresponds roughly to the expected migratory direction shown by ringing recoveries from Falsterbo (Roos 1984(Roos , A , kesson et al. 1996b). However, the radio-tracked reed warblers departed in directions slightly more towards the south, coinciding with the orientation of the nearest coastline (cf. ...
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We used radio-telemetry to study autumn migratory flight initiation and orientation in relation to wind and air pressure in a nocturnal passerine migrant, the reed warbler Acrocephalus scirpaceus at Falsterbo, southwest Sweden. The majority of the reed warblers departed in the expected migratory direction towards south of southwest, while a low number of the birds took off in reverse directions between north and east. Flight directions at departure correlated with wind directions. These correlations were particularly prominent at higher wind speeds but were absent at wind speeds below 4 m/s. Birds departing in the expected migratory direction compensated completely for wind drift. The reed warblers preferred to depart during nights with tailwinds and when air pressure was increasing suggesting that reed warblers are sensitive to winds and air pressure and select favourable wind conditions for their migratory flights. Since air pressure as well as velocity and direction of the wind are correlated with the passage of cyclones, a combination of these weather variables is presumably important for the birds' decision to migrate and should therefore be considered in optimal migration models.
... Falsterbo Bird Observatory (55°23N, 12°50E) is situated in southwesternmost Sweden (Fig. 1). Birds have been ringed there since 1947 (Roos 1984). Since 1980 a standardized ringing scheme has been in operation (Roos and Karlsson 1981), covering both spring and autumn migration seasons and ringing annually about 23 000 birds. ...
... Appendix I). Most passerine migrants passing the Falsterbo area in autumn are heading towards the south and southwest (see Roos 1984). We classified directions between 135°and 269°(SE-W) as being in agreement with the expected forward migratory directions (sectors IV, V and VI), while directions between 315°and 89°( NW-E) were considered as reverse migration (sectors VIII, I, and II). ...
... At least two different causes may explain this pattern. Many partial and irruptive migrants may settle to winter in the reverse direction (Roos 1984;Alerstam 1990a;Ketterson and Nolan 1990). This pattern applies to species such as coal tit, great tit and jay (cf. ...
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Extensive ringing data from a coastal site (Falsterbo Bird Observatory) in southwesternmost Sweden were used to investigate the occurrence of reverse autumn migration among 20 passerine bird species of widely different migration categories. The data demonstrate that reverse migration is a widespread and regular phenomenon among nocturnal as well as diurnal migrants and among irruptive migrants, temperate zone migrants, and long-distance migrants destined for tropical winter quarters. The reoriented movements were directed approximately opposite to the normal migration direction, i.e. between NNW and ENE from the coast and towards inland. Median distances of reverse movements varied between 9 and 65 km. Some individuals of irruptive and partial migrants settled to winter in the reverse direction. Bird species with relatively small fat reserves at capture were more likely to perform reverse migratory movements than species with larger fat deposits. In two species birds performing forward migration were significantly heavier within 10 days after capture than individuals performing reverse movements. The reoriented movements probably are of adaptive significance for birds confronted with the sea and pre-disposed to refuelling during migration. A bimodal orientation mechanism will bring the birds from an area with high competition for food and high predation risk to more suitable resting and feeding grounds before resuming migration in the forward direction and crossing the barrier.
... The location in southern Sweden was at Lund (55 42 0 50 00 N, 13 12 0 27 00 E) and the northern location at Abisko in northernmost Scandinavia (68 21 Karlsson et al. 2010a). Likely main breeding areas for longdistance passerine migrants passing Lund and Abisko are indicated in dark grey (Roos 1984;Strann & Bakken 2004;Karlsson 2009). ...
... The sampling periods were chosen to match the passage of long-distance migrating passerines. The most likely main breeding areas for the long-distance passerine migrants passing Lund and Abisko are indicated in Fig. 1, based on ringing recoveries from Falsterbo Bird Observatory close to Lund (Roos 1984;Karlsson 2009) and faunistic information from northernmost Scandinavia (Strann & Bakken 2004). We used two tracking radars of the same type (PV882, 200 kW peak power, 0.25 ms pulse duration, 504 Hz pulse repetition frequency, 1.5 pencil beam width, X-band). ...
Article
It has been suggested that time selection and precedence in arrival order are more important during spring than autumn migration. Migrating birds are expected to fly at faster airspeeds if they minimize duration rather than energy costs of migration, and they are furthermore expected to complete their journeys by final sprint flights if it is particularly important to arrive at the destination before competitors. We tested these hypotheses by tracking-radar studies of nocturnal passerine migrants during several spring and autumn seasons at Lund (56 degrees N) and Abisko (68 degrees N) at the southern and northern ends of the Scandinavian Peninsula, respectively. The samples from these two sites represent migrants that are mostly rather far from (Lund) or close to (Abisko) their breeding destinations. We found that the birds were flying at clearly faster airspeeds in spring than in autumn at both study sites, with spring speeds exceeding autumn speeds by, on average, 16%, after taking effects of wind conditions and vertical flight speeds into account. This difference in speeds could not be explained by seasonal differences in body mass or wing morphology and thus supports the hypothesis of time-selected spring migration. There was also a significantly larger seasonal difference in airspeed at Abisko than at Lund, suggesting that the birds may have shown an inclination to sprint on their final spring flights to the breeding destinations, although this possible extra sprint effort was modest.
... The reed warbler is a nocturnal passerine migrant wintering in tropical West Africa (Moreau 1972;Zink 1973;Roos 1984). Each autumn on average 2000 reed warblers are captured at Falsterbo Bird Observatory. ...
... According to the ringing recoveries they migrate in directions approximately between south and southwest (cf. Roos 1984;A rkesson et al. 1996b), with some performing temporary reverse migration opposite to the expected migratory direction (A rkesson et al. 1996b). ...
Article
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We used radiotelemetry to investigate the time of migratory flight initiation relative to available celestial orientation cues and departure direction of a nocturnal passerine migrant, the reed warbler, Acrocephalus scirpaceus, during autumn migration. The study was carried out at Falsterbo, a coastal site in southwest Sweden. The warblers initiated migration from times well after local sunset and well into the night, corresponding to sun elevations between -4 degrees and -35 degrees, coinciding with the occurrence of stars at night. They departed in the expected migratory direction towards south of southwest with a few initiating migration in reverse directions towards northeast to east. Flight directions under overcast conditions (7-8/8) were more scattered than under clear sky conditions (0-4/8). There were fewer clouds on departure nights than on nights when the birds did not initiate migration. For birds staying longer than one night at stopover the horizontal visibility was higher and precipitation was less likely on departure nights than on the previous night. The results show that the visibility of celestial cues, and stars in particular, are important for the decision to initiate migration in reed warblers. However, cloud cover, horizontal visibility and precipitation might be correlated with other weather variables (i.e. wind or air pressure) that are also likely to be important for the decision to migrate. Copyright 2001 The Association for the Study of Animal Behaviour.
... However, it is not known how large the wintering population is. Ringing recoveries show that also birds from Norway and Finland migrate pastFalsterbo (Roos 1984). With estimated populations of 5000 and 12000-15 000 pairs, respectively (Koskimies 1993) the proportion of foreign Sparrowhawks at Falsterbo may be quite large. ...
Article
Population estimates and number of fledged young per pair were taken from the literature to estimate the Swedish autumn population. Estimates were compared with the average numbers of migrants at Falsterbo to see how large proportion was recorded there. The proportion observed at Falsterbo varied from 1% in goshawk Accipiter gentilis to 38% in red kite Milvus milvus. Species with more southerly distribution (breeding closer to Falsterbo), like red kite and marsh harrier Circus aeruginosus were recorded to a higher degree compared to northerly species like northern harrier Circus cyaneus and rough-legged buzzard Buteo lagopus. Thermal migrants like honey buzzard Pernis apivorus, red kite and common buzzard Buteo buteo were more concentrated at Falsterbo compared to active flyers like harriers and falcons, which are less inclined to follow leading lines. In most species a higher proportion of juveniles was recorded. This may be due to adults generally wintering further north or being less inclined to follow leading lines. Honey buzzard, rough-legged buzzard and peregrine Falco peregrinus showed a higher % of adults. Here adults use their previous experience to follow established safe and efficient routes to their known winter quarters.
... The periods of autumn migration over the rest of Europe, and of wintering, are drawn from the literature (Erard 1966;Rendahl 1966;Adriaensen 1987). Robins were caught at the study stations using mist-nets and various modifications of Heligoland traps; the details of the catching routine at each station being described in other papers (Busse & Kania 1970;Hildén 1974;Roos 1984;Payevsky 1998). The numbers of recoveries of Robins from each station, and the years they operated within the study period, are presented in Table 1. ...
Article
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The pattern of the present migration routes and winter distribution of a species is the consequence of historical factors (re-colonisation from Ice-Age refugia), and of more recent evolutionary mechanisms superimposed upon this base. The present study discusses the balance between these factors as exemplified in the Robin Erithacus rubecula. The two hypotheses on the course of the species' autumn migration through the Baltic coastal area which were tested considered: (1) sequential passage of different populations, with early migrants migrating SW and later ones heading gradually more to the SE; (2) alternate passage of populations heading to the SW, SSW and SE during the season. Analysis of 1082 recoveries of Robins ringed in the autumn on the Baltic coast allowed to distinguish four main routes of passage across Europe, as used by allohiemic populations differing in timing of migration, and partly separated by migratory divides. The temporal sequence in which the routes are used by populations crossing the Baltic coastal area is in agreement with the second hypothesis. The revealed spatio-temporal segregation of Robins over the non-breeding range can provide a basis for further studies on the origin of this pattern within the species, and the mechanisms by which it is maintained.
... Autumnal fluctuations in the numbers of Great Tits at Falsterbo (Sweden, 55º22'N, 12º52'E), which is located ca 150 km inside the beech forest zone (Ulfstrand 1962; Alerstam 1993), have previously been related to the variation in the crop of beechnuts. We thus calculated the fluctuation index for the birds ringed at Falsterbo in the period 1964-80 (Roos 1984), and found it to be 25 in the case of the Great Tit, i.e. somewhat higher than the 15 and 13 noted for the Robin Erithacus rubecula and Common Redstart Phoenicurus phoenicurus respectively, but lower than the value obtained for the Dunnock Prunella modularis (FI = 42). The fluctuation index was many times greater in the Coal Tit (FI = 560), the Siskin Carduelis spinus (FI = 441) and the Long-tailed Tit (FI = 258). ...
Article
Trapping data from six ringing stations on the east coast of the Baltic Sea were used to study fluctuations in the numbers of migrating Great Tits Parus major. In the years 1971-97, the number of autumn migrating Great Tits was typically found to fluctuate less than those of partial migrants, but similarly to those of obligatory migrants at Hanko (Finland), Kabli (Estonia) and Neringa (Lithuania). The numbers of Great Tits at Mierzeja Wiślana (Poland) fluctuated more than those at the northern stations but far less than numbers among irruptive species. We found no significant correlation between the intensity of migration and: the share of young birds, the share of males and the distance between wintering grounds and ringing stations. Nor were the numbers of migrating Great Tits found to correlate significantly with the crop of beechnuts in the species' wintering area the preceding autumn. We also compared data gathered over 20 years concerning the breeding populations of 20 bird species in Białowieża National Park, eastern Poland. Numbers of breeding Great Tits were stable (like those of obligatory migrants), in contrast with the strongly fluctuating irruptive populations of Coal Tits Parus ater and Great Spotted Woodpeckers Dendrocopos major. Overall, the results indicate that Great Tits behave like regular partial migrants, with the migration in northern and eastern Europe not being affected by the crop of beechnuts in the wintering area.
... Dunnocks are predominantly diurnal migrants and birds from Scandinavia migrate towards southwest to wintering areas in Southern France and Northern Spain (Roos, 1984;Fransson et al., 2008). Both European robins and sedge warblers are nocturnal migrants (Cramp, 1988;Cramp, 1992). ...
Article
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Cue-conflict experiments were performed to study the compass calibration of one predominantly diurnal migrant, the dunnock (Prunella modularis), and two species of nocturnal passerine migrants, the sedge warbler (Acrocephalus schoenobaenus), and the European robin (Erithacus rubecula) during autumn migration in South Sweden. The birds' orientation was recorded in circular cages under natural clear and simulated overcast skies in the local geomagnetic field, and thereafter the birds were exposed to a cue-conflict situation where the horizontal component of the magnetic field (mN) was shifted +90° or -90° at two occasions, one session starting shortly after sunrise and the other ca. 90 min before sunset and lasting for 60 min. The patterns of the degree and angle of skylight polarization were measured by full-sky imaging polarimetry during the cue-conflict exposures and orientation tests. All species showed orientation both under clear and overcast skies that correlated with the expected migratory orientation towards southwest to south. For the European robin the orientation under clear skies was significantly different from that recorded under overcast skies, showing a tendency that the orientation under clear skies was influenced by the position of the Sun at sunset resulting in more westerly orientation. This sun attraction was not observed for the sedge warbler and the dunnock, both orientating south. All species showed similar orientation after the cue-conflict as compared to the preferred orientation recorded before the cue-conflict, with the clearest results in the European robin and thus, the results did not support recalibration of the celestial nor the magnetic compasses as a result of the cue-conflict exposure. © 2015. Published by The Company of Biologists Ltd.
... Robin populations from Fennoscandia, The Baltic States, and NW Russia are migratory. They spend their winter in SW Europe and the Mediterranean area (Rendahl 1966, Payevsky 1973, Roos 1984, Pettersson et al. 1986, Cramp 1988, Rezvyi et al. 1995. Nearly all authors believe that the Robin is a typical nocturnal migrant (Dorka 1966, Pettersson & Hasselquist 1985, Ehbom & Karlsson 1993, Martin 1990a, Åkesson et al. 1992, Szulc-Olech 1965, Bolshakov & Rezvyi 1998. ...
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Bolshakov, C.V. & V.N. Bulyuk (1999): Time of nocturnal flight initiation (take-off activity) in the European Robin Erithacus rubecula during spring migration: direct observations between sunset and sunrise. Avian Ecol. Behav. 2: 51-74. Temporal distribution of migratory nocturnal departures of the European Robin Erithacus rubecula, from a stopover site on the Courish Spit of the Baltic Sea, was studied systematically by direct observations (visual and searchlight methods), from sunset to sunrise over 7 years across the whole period of spring migration. Time of first take-off in spring is not fixed, day-to-day variation reaching 5.5 hours. First birds do not depart until 29-30 min after sunset. In 50% of cases spring nocturnal migration does not commence before the third hour after the sunset. The onset of nocturnal migration varies across the whole season, variation being 4.0 to 5.2 hours. The mean time of start of migration significantly shifts over the season by 45-75 min towards sun-set. During "long" nights (10-12 hours), in the first half of the migratory season, in 33% of cases the first birds do not depart until the fourth-sixth hour after sunset. During "short" nights (8-10 hours), in the second half of the season, in 95% of nights migration starts during first-third hour after sunset. Timing of nocturnal departures of Robins in spring is not synchronised and it is usually not possible to define the main departure period. Overall length of departure period reaches 9.5 hours, the latest take-off being re-corded in the tenth hour after sunset. Only 26.1% of Robins initiate flight before the end of nautical twilight (ENT). Approx. 42.5% of birds depart during the "deep" night after the end of astronomical twilight (EAT). The mean departure time in spring is 191 (SD=121) min after sunset. Only in some nights at the end of the migratory period do nearly all Robins depart during a restricted period after sunset and during twilight. All temporal characteristics of take-off activity are subject to significant changes over the season when night duration falls from 12 to 8 hours. Overall departure period changes from 9.5 to 6 hours, the mean time of nocturnal departures shifts towards sunset by more than one hour, the proportion of birds starting flight after EAT decreases, and the proportion departing before ENT increases. Inter-annual variation of temporal distri-butions of nocturnal departures, are probably related to the variation in the timing of spring migration. Within the same part of season however, inter-annual variation of the mean departure time may be over 1 hour. Variation of the mean and median departure time between successive nights of one year may also reach 1-1.5 hours. In spring Robins prefer to start migration under clear skies or slight cloud cover. As few as 9% of all birds de-parted without celestial cues visible under total overcast. Under cloudy skies, compared to clear weather, over-all departure period is longer together with the variation of the timing of departures, no seasonal trend in the mean time of start of migration and in the mean departure time is recorded and nocturnal migration in the first half of the season starts significantly earlier. The mean departure time under clear skies and high cloud scores is however, not significantly different either over the whole spring, or over fractions of the migratory period. Large variations in the timing of nocturnal departures is supposed to be caused by birds taking off, not in re-sponse to any environmental stimulus, but in respect to their individual time programmes. These programmes are a complicated manner related to seasonal LD changes and possess their own seasonal variation. A crucial factor controlling the time of nocturnal departure in spring may be the distance to the goal of migration. Con-siderable variation in the departure time basically referring to individuals approaching the goal (less then one night of flight).
... Falsterbo (FBO) data are divided into short-(short) or longdistance (long) migrants based on time of passage at Falsterbo the short-distance migrants (according to the hypothesis explained in the "Introduction") and/or a stronger relative increase in spring airspeed among the short-distance migrants. The main breeding areas for migrants passing Falsterbo seem to be similar for short-and long-distance migrants according to ringing recoveries (Roos 1984;Karlsson 2009) including mainly the southern and central parts of Fennoscandia (see map in Karlsson et al. 2012). This means that there is little reason to expect more sprint migration in one or the other category of migrants (Alerstam 2006). ...
Article
Migrating birds are expected to fly at higher airspeeds when minimizing time rather than energy costs of their migratory journeys. Spring migration has often been suggested to be more time selected than autumn migration, because of the advantage of early arrival at breeding sites. We have earlier demonstrated that nocturnal passerine migrants fly at higher airspeeds during spring compared to autumn, supporting time-selected spring migration. In this study, we test the hypothesis that seasonal airspeeds are modulated differently between short- and long-distance migrants, because of a stronger element of time selection for autumn migration over long distances. In support of this hypothesis, we demonstrate that the seasonal difference in airspeed is significantly larger (spring airspeed exceeding autumn airspeed by a factor of 1.16 after correcting for the influence of altitude, wind and climb/descent on airspeed) among short-distance compared to long-distance (factor 1.12) migrants. This result is based on a large sample of tracking radar data from 3 years at Falsterbo, South Sweden. Short-distance migrants also tend to fly with more favourable winds during autumn, indicating relaxed time constraints (being able to afford to wait for favourable winds) compared to long-distance migrants. These results indicate surprisingly fine-tuned seasonal modulation of airspeed and responses to wind, associated with behavioural strategies adapted to different levels of time selection pressures during spring and autumn migration.
... However, Dunlins ringed during migration in the Baltic have rendered numerous recoveries from moulting grounds (Pettersson et al. 1986, Clark 1989, Gromadzka 1989. This is also true at Falsterbo (Roos 1984), which is situated only 250 km from the moulting grounds in Denmark. It is also unlikely that the stopover sample is considerably biased. ...
Article
The post-nuptial primary moult of adult (2-year-birds included) Dunlins was investigated along the Baltic coast at Ottenby and Falsterbo, S. Sweden. These birds are on migration and only make short stopovers. During the years 1985-1988 at Ottenby, the proportions of moulting birds varied between 27% and 61%, probably due to annual variations in the timing of their passage. Compared with the older birds, 2-year-birds had more often initiated their moult and, on average, appeared in a more advanced stage of moult. Most of the Dunlins that had initiated moult were actively moulting - some feathers were not of full length and were found growing in a sample of caged individuals. The raggedness value (i.e. the gap due to not fully grown feathers) generally decreased in later stages of moult. By comparing raggedness values at given stages of moult, migrating Baltic birds generally had smaller gaps than non-migrating English conspecifics. Large gaps were correlated with lower body masses. The adaptive significance of commencing the moult prior to the arrival on moulting grounds and of moult during migration are discussed.
... Other details as inFig. 3 1960 , Roos 1984 ). However, first-year flycatchers display a higher directional variation than d o older birds (Rabol 1978 ). ...
Article
Release experiments were conducted to examine a number of questions concerning the orientation behaviour of free-flying birds. (1) We found distinct differences in the orientation performance of Robins released under clear and overcast skies, respectively, during autumn migration. While Robins oriented in a seasonally appropriate direction under clear skies, they selected a northwesterly mean direction under overcast, pointing to the importance of visual celestial cues during autumn migration. There was no significant difference in orientation under clear and overcast skies in releases performed during spring migration. Pied Flycatchers failed to orient in their expected migratory direction when released under clear autumn skies, probably because of strong winds. (2) The amount of stored fuel reserves had a pronounced influence on the decision to take off on migratory flights, both for Robins and Pied Flycatchers. (3) Autumn releases of Robins and Pied Flycatchers under clear skies revealed a significantly larger angular dispersion in orientation for migratorily naive (first-year) birds as compared to adults. This suggests that adult birds orient with higher precision due to experience and/or that strong selection among young migrants operates to maintain orientation within narrow limits. (4) Pied Flycatchers (long-distance migrants) vanished from view significantly faster than did Robins (short-distance migrants) when released under clear autumn skies. (5) Displacement experiments with Robins and Pied Flycatchers, captured at two different sites and then transported to a common release site, yielded inconsistent results which, in only one case out of four, could be interpreted as compensatory orientation towards the capture sites.
... Recovieres from the ares of Germany indicated Danish, Swedish and Norwegian origin of birds caught (Hudde and Vohwinkel 1997). Also the analysis of recoveries from a Swedish station Falsterbo confirmed the migration of Scandinavian Dunnocks along the western route through Germany and France (Roos 1984). It is possible that also a considerable part of birds caught at Bukowo-Kopañ have similar origin, but the lack of the species recoveries from this station does not allow to state this unambiguously. ...
Article
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Autumn Migration Dynamics and Biometrical Differentiation of the Dunnock (Prunella modularis) Passing the Southern Baltic Coast The aim of this study is to determine biometrical differentiation among Dunnocks caught at the two ringing sites (Bukowo-Kopań and Mierzeja Wiślana) located on the southern Baltic coast. The distance between those two stations covers 190 km. The material was collected during autumn fieldwork of the Operation Baltic in 1961-2003. The material used for biometrical analysis comprises only immature birds from the period of the most intensive migration, when the numbers of caught individuals allowed to compare the results for both stations. The seasonal dynamics at both sites was pooled for 43 years of catching. Medians of autumn migration for the stations were significantly different. A shift of the median for the eastern site (Mierzeja Wiślana) by 6 days after the median for the western site (Bukowo-Kopań) suggested different origins of birds migrating through the stations. The analysis of standard deviations for the studied biometrical parameters confirms an intra-seasonal change in proportions of birds probably originating from different areas in Europe.
... yearly in the continent (Devort 1997). Thus, the ringing recovery rate of this species is high, although variable within the different countries (Dhont and van Hecke 1977, Fog 1978, Kålås 1980, Roos 1984, Pörner 1987, Kharitonov 1998, Meissner 2000, Švažas et al. 2001). Distributions of the Common Snipe ringing recoveries have been depicted for Central Europe (Glutz von Blotzheim et al. 1977), Denmark (Fog 1978), Fennoscandia (Kålås 1980) and former USSR (Baumanis 1985 ). ...
Article
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The autumn migration of the Common Snipe was studied in years 1983-2000 in western part of the Gulf of Gdaæsk (Polish Baltic coast). In this period 1763 birds were ringed and 50 long-distance recoveries were obtained. The Common Snipe is one of the favoured game birds and the obtained recovery rate (2.8%) is rather high in comparison with other wader species ringed on the Gulf of Gdaæsk coast (Meissner and Remisiewicz 1998). After leaving the Gulf of Gdaæsk the birds continue their migration in western direction. The majority of them were recorded in France (62%) and Great Britain (20%). The bulk of records were concentrated along the English Channel and the Gulf of Biscay coasts. Although 88% of recovered Common Snipes were shot, there were only 4 recoveries from the western Medi- terranean and not one recovery from the Apennine Peninsula, where hunting pressure is very high. It suggests that Common Snipes passing northern Poland follow almost exclusively the southern Baltic and the southern North Sea coasts and their main wintering grounds stretch from Denmark, through northern France, to the Pyrenees. The recovery rate of birds ringed in July was over twice as high as in August and September, in spite of the fact that the majority of Common Snipes was passing the study area between the second decade of August and the end of September. Reasons for differences in recovery rate among birds ringed in subsequent months and in different years are discussed. The average speed of migration calculated on the basis of autumn direct recoveries was only 22.6 km/day (SD = 13.3, N = 17). It confirms that Common Snipes move slowly in autumn. The species adheres to the B-strategy sensu Alerstam and Hgstedt (1982) and migrates in autumn in short flights with very low fat reserves.
... The Robins breeding in Scandinavia and Finland are migratory birds (nocturnal migrants). Their wintering areas are situated in south-western Europe and the Mediterranean region (Rehndahl 1966, Roos 1984, Pettersson etal. 1986, Cramp 1988. ...
Article
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The biometrics, age ratio and timing of migration of Robins were compared during autumn migration at an inland and a coastal site 200 km apart. The proportion of adult birds was higher at the inland site. The time of peak of migration differed between the two sites by 9 days. The daily distribution showed that at the coastal site the birds made a land‐fall at dawn, while at the inland site the migration continued during the morning.Robins in the same visual fat class were heavier at the inland site, but their mean fat class was lower than at the coastal site. This would be expected if Robins inland were short‐stage migrants and therefore do not need extensive fuel reserves. At the coastal site a higher proportion of the Robins are probably long‐stage migrants.The orientation of the Robins under clear skies was more south‐westerly at the coastal site. The direction is significantly different from the mean azimuth of sunset at the coastal site only. Under totally overcast conditions the directions were more scattered at both sites, indicating the importance of visual cues for orientation.
... One aim of the present study was therefore to compare trends and patterns in passage time for a number of species at two different sites: our study site Ottenby in Sweden and at Helgoland, situated some 600 km WSW of Ottenby, as studied by Hü ppop and Hü ppop (2003), where methods of data collection and analysis were almost identical. Given that most migrants in western Europe move towards north-east in spring, these two sites are more or less along the same migration route for many species (Roos 1984, Liljefors et al. 1985, Hü ppop and Hü ppop 2003. Forchhammer et al. (2002), Tryjanowski et al. (2002) andHü ppop andHü ppop (2003) suggested that birds which follow a central or easterly route through Europe in spring should be less affected by NAO than those following a westerly route, given that the influence of NAO on local climate should decrease with increasing distance from the Atlantic coast . ...
Article
We studied long-term trends and the yearly variation in mean spring passage time in 36 passerine bird species trapped at Ottenby Bird Observatory in south-eastern Sweden. Between the years 1952–2002, data were available for 22–45 years depending on species. Most long-distance migrant species passed progressively earlier over the study period (range: 2.5 days earlier to 0.7 days later per 10 years, with an average of 0.9 days earlier per 10 years). The annual variation in timing of migration in most species, regardless of migration distance, correlated negatively with the winter index of the North Atlantic Oscillation (NAO), a large-scale climate phenomenon influencing the climate in the North Atlantic region. Birds passed earlier after mild and humid winters, corresponding to the high phase of the NAO. This corroborates the pattern found at a nearby migration site with a comparable dataset (Helgoland, 600 km WSW of Ottenby). However, short/medium-distance migrant species at Ottenby, in contrast to the situation at Helgoland, have shown no general trend of earlier passage in recent years. This was probably a consequence of the shorter study period at Ottenby, which included only the last 22–32 years (41 years at Helgoland), when the NAO showed no significant trend. At the species-specific level, the long-term trends in passage time were similar at the two sites, and there was some congruence to the extent that a given species was affected by NAO. Long-distance migrants wintering south and south-east of the breeding grounds showed some of the strongest changes in long-term trends (passing progressively earlier) at Ottenby, and for some of these species passage time varied negatively with NAO. Obviously, and contrary to previous suggestions, variations in NAO also influence birds migrating through eastern Europe, although the direct or indirect mechanisms through which this is achieved are unknown.
... A division of the migratory journey into distinct legs, each with a different main orientation, and with disparate autumn and spring configurations, is by no means restricted to the wheatear. Another good example is the willow warbler Phylloscopus trochilus, for which ringing data show different broad annual migration trajectories for populations breeding in southern and western Scandinavia (Roos, 1984) and in northern Scandinavia and Finland, respectively, as schematically drawn in Fig. 2 (Hedenström and Pettersson, 1987). Bird migration atlases compiled on the basis of ringing results (Zink, 1973(Zink, -1995Zink and Bairlein, 1995) provide evidence of several similar cases and constitute a most valuable source demonstrating differential migration patterns between populations and seasons. ...
Article
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The Common Snipe Gallinago gallinago migrates in large numbers through central Europe towards its wintering grounds in western Europe. Over the past 20 years more than 12 000 Common Snipes were ringed at seven ringing stations in Poland during their autumn migration. Birds migrating along the Baltic coast tended to spend the winter in more northern areas than those that used southern Poland as stopover sites during migration. This pattern supports the hypothesis of a parallel autumn migration exhibited by Common Snipe. Additionally, snipes passing through Poland at the beginning of the autumn migration (originating from near breeding areas) overwintered further north than later migrants (known to originate from more northern areas), which is consistent with a leap-frog migration pattern. Our results suggest that the migration pattern of the Common Snipe is more complex than previously thought, because these birds use a combination of two different non-exclusive migratory patterns.
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Reoriented autumn migration of chaffinches and bramblings occurs regularly in southernmost Sweden. The reoriented birds fly in a northeasterrly direction from the coast and inland, i.e. approximately opposite to the normal autumn migration direction. The daily peak of reoriented finch migration, as observed at inland sites 20–40 km from the coast, occurs on average 3.5 h later than the early morning departure in the normal migratory direction, and 1 h later than the peak of migration at the coast. According to trapping data the average weight of reoriented migrants and birds interrupting their migration at the coastline is significantly lower than the weight of migrants proceeding in the normal direction, and the proportion of yearlings seems to be larger in the former category. Censuses of flocks of resting finches showed that they mainly forage at stubble fields of summer rape Brassica napus, preferably fields surrounded by wooded vegetation offering shelter from predator attacks. Preferred food and habitats are mostly located inland, 20 km or more from the coast. These findings are consistent with the interpretation that reorientation constitutes an adaptive response by migrants with small fat reserves. When confronted with an ecological barrier, they return to suitable resting sites for restoring the fat reserves before crossing the barrier.
Article
An advanced orientation capability offers possibilities for birds to optimize movement patterns in a wide variety of ecological situations. The adaptive significance of various patterns of angular dispersion and of orientation responses to topography and sociality are elucidated. The orientation capacity is characterized by flexibility, exemplified by reorientation, promoting safety and restoration of fat reserves during migration. There are also limitations to the orientation process, leading to costs of migration through mis- or disorientation, and to constraints on the evolution of routes and timing of migratory flights. Young migrants may acquire an erroneous compass sense, and misorient several thousands of kilometers off their normal course. Widespread and dense fog of long duration causes disorientation and mortality among land birds migrating over the sea. Orientational constraints in the evolution of migration routes may be most easily disclosed at high geographic and magnetic latitudes. Here the birds are faced with special difficulties in using their celestial as well as their magnetic compasses. The sun compass could be used for great circle orientation, but observed spring flight trajectories of high-arctic waders and geese seem to conform with rhumbline routes.
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