Movements by juvenile and immature Steller's Sea Eagles Haliaeetus pelagicus tracked by satellite

Twenty‐four juvenile Steller's Sea Eagles Haliaeetus pelagicus were tracked via satellite from natal areas in Magadan, Kabarovsk, Amur, Sakhalin and Kamchatka. Nestling dispersal occurred between 9 September and 6 December (n = 24), mostly 14 September–21 October, and did not differ among regions or years. Most eagles made stopovers of 4–28 days during migration. Migration occurred 9 September–18 January, mostly along previously described routes, taking 4–116 days to complete (n = 18). Eagles averaged 47.8 km/day excluding stopovers; 22.9 km/day including stopovers. The mean degrees of latitude spanned during migration was: Kamchatka, 2.1; Magadan, 11.6; Amur, 7.3; and Sakhalin, 1.1. Eagle winter range sizes varied. Eagles concentrated in 1–3 subareas within overall winter ranges. The mean size of the first wintering subareas was 274 km², the second 529 km², and the third 1181 km². Second wintering areas were south of first wintering areas. Spring migration started between 2 February and 31 March. Two eagles from Magadan were tracked onto summering grounds, well south of their natal areas. Both had early and late summering areas. One bird was followed for 25 months. It initiated its second autumn migration in the first half of October and arrived on its wintering grounds on 26 December. The second autumn migration covered 1839 km (20.9–22.4 km/day). Unlike its first winter when it used two subareas, this bird used only one subarea in 1998–99, but this was located near wintering areas used in 1997–98. It left its wintering ground between 13 April and 13 May, and arrived on its summering grounds between 7 June and 8 July. Unlike most satellite radiotracking studies, data are presented from a relatively large number of birds from across their breeding range, including new information on eagle movements on the wintering grounds and during the second year.     

Comparative nest habitat characteristics of sympatric White‐tailed Haliaeetus albicilla and Golden Eagles Aquila chrysaetos in western Scotland

Capsule Golden and White‐tailed Eagles selected different habitats for nesting.

Aim To investigate differences in nesting habitat used by sympatrically breeding eagles in western Scotland, following reintroduction of White‐tailed Eagles from 1975 onwards.

Methods Nest‐site locations from national surveys in 2003–05 were entered into a geographical information system (GIS) in order to measure a set of geographic parameters for each nest site. Binary logistic regression with backwards deletion of non‐significant terms was used to derive minimum adequate models at two spatial scales of the likelihood of an eagle nest belonging to one species or the other. We compared changes in occupancy between 1992 and 2003 of Golden Eagle territories inside and outside a GIS model of potential White‐tailed Eagle habitat and according to proximity to White‐tailed Eagle nests.

Results White‐tailed Eagles nested at lower altitudes than Golden Eagles, in more wooded habitats with more open water close by, tending to nest in trees where these were present. There were 3359 km² of potential White‐tailed Eagle nesting habitat within 25 km of existing White‐tailed Eagle nests, containing 54 Golden Eagle territory centres, but we found no difference in change of occupancy for Golden Eagle territories close to White‐tailed Eagles compared with those further away.

Conclusion White‐tailed and Golden Eagles appear to partition nesting habitat in the west of Scotland by altitude. This corresponds with behaviour in western Norway and with the situation described in historical accounts of nest‐sites in western Scotland prior to extinction of White‐tailed Eagles. It is also consistent with recent studies showing little overlap in breeding season diet of Golden and White‐tailed Eagles in western Scotland, and likely partitioning of foraging habitat by altitude. We conclude that the likelihood of competitive exclusion is less than previously suggested.     

Individual variation in orientation promotes a 3000‐km latitudinal change in wintering grounds in a long‐distance migratory raptor

Migrating juvenile birds rely on endogenous information in choosing the direction in which to fly, but such input may be overridden by social interactions with experienced individuals. We tagged seven juvenile Short‐toed Eagles Circaetus gallicus with GPS transmitters in southern Italy. This trans‐Saharan migrant flies mainly by soaring and is therefore not well adapted to performing long water crossings. Five of the seven tagged juveniles used the longer but apparently safer route towards the Strait of Gibraltar, and two migrated along a southerly trajectory and subsequently spent the winter in Sicily, apparently forced to do so by the 150‐km‐wide Sicily Channel. One of these individuals took the longer route the following autumn. These results, combined with long‐term (15 years) visual field observations involving thousands of individuals, suggest that inexperienced Short‐toed Eagles may learn their migratory routes from experienced adults, whereas some of them migrate south in response to an innate orientation instinct. Transport costs, inherited information and geography apparently interact, forcing some Short‐toed Eagles to winter 3000 km to the north of the majority of their conspecifics.     

Age-related timing of Short-toed Snake Eagle Circaetus gallicus migration along detoured and direct flyways

Capsule: Juvenile Short-toed Snake Eagles Circaetus gallicus hatching in the peripheral populations of Greece and Italy have limited opportunities for social learning of migration routes compared to those hatched elsewhere.

Aims: To test the prediction that there would be a higher degree of migration synchrony between adult and juvenile Short-toed Snake Eagles originating from peripheral populations and using an extremely detoured flyway, when compared to other populations using a direct overland flyway.

Methods: We use linear regression models to compare seasonal changes in the age distribution of migrating Short-toed Snake Eagles counted at two migration watch-sites in Italy (Arenzano) and Georgia (Batumi), along a detoured and a direct flyway, respectively.

Results: Juveniles migrated a few days later than adults at both sites and the age ratios recorded at these two sites was similar. The daily proportion of juveniles increased along a similar slope during the migration season, thus showing a similar degree of synchrony between the age classes on both flyways.

Conclusions: Contrary to our hypothesis, juvenile and adult migration is not more synchronized in peripheral populations using a detoured flyway compared to a core population using a direct migration flyway. Our results suggest that juveniles do not learn detours to complete trans-Mediterranean migration from their parents, but from other elders.     

Breeding status and ecology of the Martial Eagle in the Kalahari Gemsbok National Park,South Africa

Herholdt, J.J. & Kemp, A.C. 1997. Breeding status and ecology of the Martial Eagle in the Kalahari Gemsbok National Park. Ostrich 68 (24): 80–85.

The success of 16 nesting areas (territories) of Martial Eagles was monitored for seven successive years (1988–1994) in a protected area in the Kalahari desert of South Africa. Martial Eagles mostly laid in consecutive years (38 out of 53 attempts) and fledged, on average, 0.43 young/pair/year (38/88). Most Martial Eagles laid eggs in May and June (72.2%; n = 13 attempts). Almost all located Martial Eagle nests were in the Acacia erioloba savanna in the dry Auob and Nossob riverbeds. Martial Eagle nesting areas were spaced at intervals of 24.1 km (1144.6 km; n = 6) along the Nossob River, 15.1 km (8–34 km; n = 7) in the Auob River and 31.3 km (25–43 km, n = 4) in the interior dune area. A total of between 20 and 30 Martial Eagle pairs (20 known active nesting areas) occurred in the Kalahari Gemsbok National Park during the study period. There was no evidence of a decline in active nesting areas of Martial Eagles during the seven year study. There was no safe buffer zone around the Kalahari Gemsbok National Park and Martial Eagles were at times persecuted when foraging in the adjacent farmlands.     

Hints on Research for Bird-watchers

Capsule Fledgling Golden Eagles in northern Sweden preferred clearcuts and other open forest habitats, as well as steep slopes.

Aims To study the post-fledging habitat use and ranging behaviour of juvenile Golden Eagles on their natal territories.

Methods Fourteen juvenile Golden Eagles in northern Sweden were marked with GPS transmitters and tracked until they left their natal territory.

Results Eagles fledged at the end of July–beginning of August and remained on their natal territories until October–early November. Fledged eagles' home range size before flying south was on average 41?km². Juvenile eagles showed a preference for clearcuts, coniferous forest on lichen-covered bedrock and edges between clearcuts and forest, whilst all other habitat types were used less than expected. The eagles showed a preference for steep slopes, in particular south-facing ones, whilst north-facing slopes were used less than expected.

Conclusion Golden Eagles' preference for clearcuts and steep slopes can be used in the planning and management of ‘eagle friendly’ wind farms.     

Migration of the Little Ringed Plover Charadrius dubius breeding in South Sweden tracked by geolocators

Capsule Little Ringed Plovers breeding in South Sweden migrate towards the southeast in the autumn, via the Middle East, to winter in Saharan and sub-Saharan locations or in India, while the spring migration is more directly towards the north.

Aims To study the migration routes and wintering area of Little Ringed Plovers (Charadrius dubius) breeding in South Sweden, and to investigate the migration strategy and speed for this little studied shorebird.

Methods We use light-level geolocators to track the year-round movements of Little Ringed Plovers breeding in South Sweden.

Results Autumn migration proceeded towards the southeast, in three birds via lengthy stopovers in the Middle East, followed by movements towards the west and southwest to final winter destinations in Africa, while one male made a long stopover in northwestern Iran before migrating to India. The birds wintering in Africa probably stayed at freshwater locations in the Sahara or just south or north of the Sahara. Spring migration was more directly back to the breeding area. Overall migration speeds were similar during autumn and spring migration at about 189 and 209?km/day, respectively. The migration was carried out mainly as many short flights between stopovers. In particular, autumn migration was longer than the direct distance between breeding and wintering sites.

Conclusions This study shows that the geolocator method can successfully be used with relatively small (40?g) shorebirds. We found that a local population of Little Ringed Plover may have widely differing wintering sites (low connectivity), from sub-Saharan Africa to the Indian subcontinent. The migration strategy of the Little Ringed Plover, with multiple short flights, deviates from that of many other long-distance migrating shorebirds that, instead, make one or a few long flights.     

Spatial distribution and breeding territories of Bonelli’s Eagle Aquila fasciata in the western Anti-Atlas Mountains,Morocco

The North African population of Bonelli’s Eagle Aquila fasciata (Vieillot, 1822) is limited to the south by the northern fringe of the Sahara Desert. This study provides the first data on the spatial distribution and density of breeding Bonelli’s Eagles in south-west Morocco, at the southern limit of their breeding distribution in the Western Palearctic. We used broad-scale sampling to investigate spatial patterns in occupancy of territorial pairs of Bonelli’s Eagles in an area of ～29 715 km2 in the western Anti-Atlas Mountains, southern Morocco, during 2016–2018. We found 28 nesting territories containing 40 used nests, heterogeneously distributed in areas of high topographic variation, from 60 to 1 890 m asl. The average nearest-neighbour nest distance was 14.12 ± 9.90 km and varied from 2.65 km in the north-west to 37.80 km in the pre-Saharan lands in the south-west portion of the study area. This work shows the importance of the western Anti-Atlas Mountains as one of the most significant strongholds of the species in Morocco. However, there is a need for systematic analyses of the different factors affecting the distribution of the species to implement conservation actions of this peripheral population.     

Seasonal migrations of four individual bar-headed geese Anser indicus from Kyrgyzstan followed by satellite telemetry

The Kyrgyz population of the bar-headed goose Anser indicus has declined dramatically during the past decades. Human persecution during migration and habitat loss at stopover and wintering sites are commonly regarded as most serious threats. However, little is known about seasonal movements, migration routes, and wintering sites of the bar-headed geese from Kyrgyzstan, which represent the westernmost geographical population of the species. As part of a conservation project, which also included reinforcement of the wild population by the release of hand-reared juveniles, in late summer of 1998, five bar-headed geese, three wild adults and two hand-reared goslings, were fitted with sun-powered satellite transmitters in order to track their movements from Lake Son Kul and Lake Chatyr Kul in Kyrgyzstan. The five individuals contributed very unevenly to the more than 5,000 signals in total that were received from the French ARGOS system: one failed after 8 weeks, while another one was tracked for more than 2 years. The four geese contributing to this study followed three completely different migration routes leading to their wintering areas in Pakistan, India and Uzbekistan, while stopover areas were situated in southern Tajikistan and in western Tibet. Both in autumn and spring the adult birds migrated distances of 1,280–1,550 km in two steps, with stopover periods of 32–46 days (autumn) and 16–23 days (spring). Flight speeds of up to 680 km per actual migration day were recorded regularly, even during crossings of very high summits. A hand-reared juvenile flew non-stop for 790 km to southern Uzbekistan and even visited southernmost Turkmenistan, where the species is very rarely seen. The timing of migration varied considerably between individuals but also for the same individual between years. We compare our tracking results with previous findings (field observations, ring recoveries, and satellite tracking results) and discuss them with respect to migration over high-mountain habitats and a general migration strategy of the species.     

Migration routes and stopover sites of Black-necked Cranes determined by satellite tracking

ABSTRACT.   Because their breeding and wintering areas are in remote locations, little is known about the biology of Black-necked Cranes ( Grus nigricollis ), including their migratory behavior. Using satellite telemetry, we monitored the migration of Black-necked Cranes ( N = 6) in China to determine migration routes and the location of stopover sites. From 2005 to 2007, four cranes were tracked during two spring migrations and one fall migration, one was tracked during one spring and one fall migration, and one was tracked during one spring migration. On average, the cranes made seven flights over a 5-d period to migrate 651 km to breeding areas in the spring. In the fall, birds averaged six flights in 5 d to migrate 694 km. The routes traveled by cranes during spring and autumn migration were similar. Both the migration distances and duration of migration are the shortest reported for any crane species to date. Most stopover sites were in areas along rivers and close to wetlands in the Daliang Mountains and the Ruoergai Plateau. Conservation measures are needed to reduce habitat loss (wetland and pasture) in the Daliang Mountains and establish a reserve for stopover sites in the Ruoergai marshes, such as Longriba and Bai River in Hongyuan County.     

Effects of a sea barrier on large-scale migration patterns studied by a network of weather radars

Capsule: Nocturnal passerine migration patterns were studied by a network of weather radars within the East-Atlantic flyway providing large-scale information on the effect of a geographical barrier.

Aims: The aim of this study was to obtain a large-scale spatial overview of the effects of a sea barrier on migratory flyways in northern Spain/western France.

Methods: Weather radar data were used from five sites at the Bay of Biscay during nights in spring 2015 to calculate flight directions and migration traffic rates (MTRs).

Results: The highest MTRs were registered by the radars at the southeastern edge of the bay, with a gradual decrease northwards. Spring migration direction was generally NNE/NE. Continuous nocturnal migration pattern indicated migration over land in the south. The radar half way up the French coast exhibited bimodal migration intensities at night, indicating sea crossing, and the northernmost corner of the bay showed little migration.

Conclusions: Radar patterns indicated migration over land and sea during spring migration. Sea crossing occurred with flight distances of up to about 500?km. Most migration activity was observed in the radars along the southeastern section of the bay, indicating that the general migration flyway from Spain funnels through the eastern side of the north Iberian Peninsula.     

Movements and landscape use of Eastern Imperial Eagles Aquila heliaca in Central Asia

Capsule: We describe ecological factors associated with movements of a globally declining raptor species, the Eastern Imperial Eagle Aquila heliaca.

Aims: To describe the movements, habitat associations and resource selection of Eastern Imperial Eagles marked in Central Asia.

Methods: We used global positioning system (GPS) data sent via satellite telemetry devices deployed on Eastern Imperial Eagles captured in Kazakhstan to calculate distances travelled and to associate habitat and weather variables with eagle locations collected throughout the annual cycle. We also used resource selection models to evaluate habitat use of tracked birds during autumn migration. Separately, we used wing-tagging recovery data to broaden our understanding of wintering locations of eagles.

Results: Eagles tagged in Kazakhstan wintered in most countries on the Arabian Peninsula, as well as Iran and India. The adult eagle we tracked travelled more efficiently than did the four pre-adults. During autumn migration, telemetered eagles used a mixture of vegetation types, but during winter and summer, they primarily used bare and sparsely vegetated areas. Finally, telemetered birds used orographic updrafts to subsidize their autumn migration flight, but they relied on thermal updrafts during spring migration.

Conclusion: Our study is the first to use GPS telemetry to describe year-round movements and habitat associations of Eastern Imperial Eagles in Central Asia. Our findings provide insight into the ecology of this vulnerable raptor species that can contribute to conservation efforts on its behalf.     

Spring migratory routes and stopover duration of satellite‐tracked Eurasian Teals Anas crecca wintering in Italy

Identifying an organism's migratory strategies and routes has important implications for conservation. For most species of European ducks, information on the general course of migration, revealed by ringing recoveries, is available, whereas tracking data on migratory movements are limited to the largest species. In the present paper, we report the results of a tracking study on 29 Eurasian Teals, the smallest European duck, captured during the wintering period at three Italian sites. The departure date of spring migration was determined for 21 individuals, and for 15 the entire spring migratory route was reconstructed. Most ducks departed from wintering grounds between mid‐February and March following straight and direct routes along the Black Sea‐Mediterranean flyway. The breeding sites, usually reached by May, were spread from central to north‐Eastern Europe to east of the Urals. The migratory speed was slow (approximately 36 km/day on average) because most birds stopped for several weeks at stopover sites, mainly in south‐eastern Europe, especially at the very beginning of migration. The active flight migration segments were covered at much higher speeds, up to 872 km/day. Stopover duration tended to be shorter when birds were closer to their breeding site. These results, based on the largest satellite tracking effort for this species, revealed for the first time the main features of the migratory strategies of individual Teals wintering in Europe, such as the migration timing and speed and stopover localization and duration.     

Narrow-Front Loop Migration in a Population of the Common Cuckoo Cuculus canorus,as Revealed by Satellite Telemetry

Narrow migration corridors known in diurnal, social migrants such as raptors, storks and geese are thought to be caused by topographical leading line effects in combination with learning detailed routes across generations. Here, we document narrow-front migration in a nocturnal, solitary migrant, the common cuckoo Cuculus canorus, using satellite telemetry. We tracked the migration of adult cuckoos from the breeding grounds in southern Scandinavia (n = 8), to wintering sites in south-western Central Africa (n = 6) and back to the breeding grounds (n = 3). Migration patterns were very complex; in addition to the breeding and wintering sites, six different stopover sites were identified during the 16,000 km annual route that formed a large-scale clockwise loop. Despite this complexity, individuals showed surprisingly similar migration patterns, with very little variation between routes. We compared observed tracks with simulated routes based on vector orientation (with and without effects of barriers on orientation and survival). Observed distances between routes were often significantly smaller than expected if the routes were established on the basis of an innate vector orientation programme. Average distance between individuals in eastern Sahel after having migrated more than 5,000 km for example, was merely 164 km. This implies that more sophisticated inherent guiding mechanisms, possibly involving elements of intermediate goal area navigation or more elaborate external cues, are necessary to explain the complex narrow-front migration pattern observed for the cuckoos in this study.     

Spatial distribution of undulating flight displays of territorial Golden Eagles Aquila chrysaetos in Lewis,Scotland

ABSTRACT

Capsule: The undulating display flight of Golden Eagles Aquila chrysaetos has a territorial function on current consensus: we found that displays could occur at any location within a home range of territorial birds and were not more frequent at the territorial limits (as documented by a previous study) or around the nest site.

Aims: To test the null hypothesis that display activity does not spatially differ within the home range of territorial Golden Eagles.

Methods: We used 1488?h of observations of Golden Eagles between April 2003 and October 2004 (excluding November through January inclusive) on the Isle of Lewis, northwest Scotland involving primarily four territories. Territorial boundaries and nest sites were determined by the behaviour of the focal territorial birds. All flight activity was cast into three spatial categories (near-boundary, near-nest and elsewhere) and the relative occurrence of displays was referenced by overall flight activity recorded in these spatial categories.

Results: We failed to reject the null hypothesis. Prior findings of greater display rate at territory limits were not confirmed. Territorial Golden Eagles apparently displayed wherever they happened to be in their home range. There was no difference in display frequency between successful and failed breeding pairs and, within pairs, between successful and failed breeding seasons. Monthly changes in display activity did not differ from monthly changes in the presence of ‘intruding’ sub-adults. A peak in non-territorial bird activity in August and September was not reflected by a peak in display, however, we could not distinguish recently fledged ‘non-threatening’ birds in this period.

Conclusions: Undulating flight displays of Golden Eagles focused neither on territory boundaries nor the nest. Displays may be spontaneous or occur in response to the detection of potential trespassers or neighbours, however, we could not rule out any role of pair-bonding.     

Migration route and spawning area fidelity by North Sea plaice

Data from plaice, Pleuronectes platessa L., tagged with electronic data storage tags, were used to test whether these fishes exhibited migration route and spawning area fidelity in successive spawning seasons. Depth and temperature data were recorded for each fish over 365-512 days in the central North Sea and this information was used to reconstruct movements based on tidal locations. We discovered highly directed seasonal migrations from the winter spawning area south of a major topographical feature, Dogger Bank Tail End, to summer feeding grounds 250 km to the north in deep, cold, thermally stratified water. Our results show synchronous timing of migration, repeated pre- and post-spawning migration routes and 100% spawning area fidelity, including two individuals that returned to within 20 km of their previous season's spawning location. This is the first study to provide a complete reconstruction of annual migrations by individual fishes, showing strong homing behaviour along consistent migration routes.     

Post-fledging migration of common murres Uria aalge in the Baltic Sea: management implications

In this study of common murre Uria aalge chicks, at Slora Karlsö in the Baltic Sea (Sweden), we used two data sets to investigate the post-fledging migration to learn more on potential threats from human activities. Firstly, we radio tracked 12 chicks on average 5.1 h during their first night at sea, after jumping from the breeding cliffs in early July. Their average speed was 1,9 km h-'and all chicks swam in a similar direction (SW) with a mean bearing of 235°. By searching an area of ca 400 km2 further off the island between two and six days after the radio tracking, we concluded that they did not stop, even temporarily, within 40 km off the island, but had continued the swimming migration. Our second data set was made up by 400 recoveries of ringed chicks. Only those recovered within eight months after fledging (until February) were included. Two birds recovered at the Polish coast in the beginning of August had moved on average 10.7 and 12.3 km day-'(i.e. 0.45-0.51 km h-). In August, all chicks, except one, were found south of Gotland > 70 km away. The average distance to the recovery sites in. August was 253.5 km (n = 11). The pattern of distribution of birds reported in September. October and during the winter period from November to February was about the same as in August. The average direction from the colony lo the recovery sites was S to SW. Important findings from nature management perspective are: 1) our data suggest that the route of the chicks at least partly coincide with ship routes with at least 42000 passages each year. Hence, there is a potential for a great part of the common murre population to get in contact with oil spillage at this stage, notably in the first half of July. 2) From the 400 reported recoveries of ringed chicks we concluded that the most important over wintering areas are around Bornholm and the Bay of Gdansk. Hence, these are the most likely areas for conflicts with the fishery and oil spillage during the winter.     

Converging migration routes of Eurasian hobbies Falco subbuteo crossing the African equatorial rain forest

Autumn migration of adult Eurasian hobbies Falco subbuteo from Europe to southern Africa was recorded by satellite telemetry and observed routes were compared with randomly simulated routes. Two non-random features of observed routes were revealed: (i) shifts to more westerly longitudes than straight paths to destinations and (ii) strong route convergence towards a restricted area close to the equator (1 degree S, 15 degrees E). The birds migrated south or southwest to approximately 10 degrees N, where they changed to south-easterly courses. The maximal spread between routes at 10 degrees N (2134 km) rapidly decreased to a minimum (67 km) close to the equator. We found a striking relationship between the route convergence and the distribution of continuous rainforest, suggesting that hobbies minimize flight distance across the forest, concentrating in a corridor where habitat may be more suitable for travelling and foraging. With rainforest forming a possible ecological barrier, many migrants may cross the equator either at 15 degrees E, similar to the hobbies, or at 30-40 degrees E, east of the rainforest where large-scale migration is well documented. Much remains to be understood about the role of the rainforest for the evolution and future of the trans-equatorial Palaearctic-African bird migration systems.     

Satelliten-Telemetrie beim Wei?storch (Ciconia ciconia) auf dem Wegzug — eine Pilotstudie

Zusammenfassung (1) 1991 konnten erstmals 4 mit Kleinsendern ausgerüstete Weißstörche mit Hilfe der Satelliten-Telemetrie auf Teilstrecken ihres Wegzugs bis zu 46 Tage lang verfolgt werden. Die japanischen Sender betrugen nur etwa 2 % des Körpergewichts der Vögel; die Ortung erfolgte durch das ARGOS-System. Die Versuchsvögel zeigten völlig normales Zugverhalten. — (2) Drei der in Brandenburg und Sachsen-Anhalt markierten Vögel waren Ostzieher und konnten über Strecken von etwa 640–4700 km verfolgt werden, 1 Storch bis zur ägyptisch-sudanesischen Grenze. Ein Westzieher konnte rund 1400 km bis zu den Pyrenäen geortet werden. — (3) Die Vögel wanderten individuell recht verschieden. 2 zogen weitgehend kontinuierlich bis in den Sudan bzw. zu den Pyrenäen, die anderen legten längere Pausen ein. Die ermittelten Zugstrecken verliefen recht geradlinig; Richtungsänderungen erfolgten vor allem an der Donau, den Karpaten, am Mittelmeer und auf der Sinai-Halbinsel. Tagesetappen betrugen mindestens bis zu 370 km, in einem Fall in 21 Tagen durchschnittlich 224 km/Tag. Die Zuggeschwindigkeit lag in der Größenordnung von 30–90 km/h. — (4) Verbesserte Sender mit längerer Lebensdauer und mehreren Ortungen pro Tag dürften es bald ermöglichen, individuelle Wanderrouten von Weißstörchen und anderen Großvögeln praktisch lückenlos zu ermitteln. Begleitmannschaften werden zudem die Zug- und Rastökologie mit Sendern ausgerüsteter Vögel mit erfassen können. Damit dürfte der Vogelschutz auf dem Zug eine neue Dimension gewinnen.

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Satellite tracking of White Storks during the autumn migratory period — a pilot study

Summary (1) In 1991 parts of the routes of White Storks migrating in autumn could be recorded for the first time by satellite tracking. Four individuals could be followed for up to 46 days. Transmitter weight accounted for only about 2 % of body mass. Locations were obtained by the ARGOS system. Migratory behaviour of the experimental birds appeared to be absolutely normal. — (2) The birds were equipped with transmitters in eastern Germany. Three of them followed the eastern migration route and could be tracked from 640 up to 4700 km, the latter reaching the borders of Egypt and Sudan. A western migrant could be followed over a distance of about 1400 km towards the Pyrenees. — (3) Migration showed considerable individual variation. Whereas in two birds migration was largely continuous towards the Sudan and the Pyrenees, respectively, the other birds rested for longer periods. The tracked migration routes were fairly straight. Marked directional shifts occurred towards the Danube valley, at the Carpathian mountains, the Mediterranean and on the Sinai. Capacity per day was at least 370 km. One bird covered 224 km/day on average during a period of 21 days. Migration speed ranged in the magnitude of 30–90 km/h. — (4) Improved transmitters with increased lifetime giving several locations per day will presumably allow to record migration routes of White Storks and other large birds more completely in the near future. Escorts should then be able to closely analyse the ecology of migration and staging of their test birds. These possibilities may give a new dimension to bird conservation measures during migration.