Bird Migration Dear Readers

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Bird migration Dear Readers,

The world of birds is full of fas- begin their migration to Africa into English and published it elec- cinating stories. Perhaps one of in August to spend the winter tronically. The PDF file is to be the most impressive is the annual in central Africa. In April they distributed free of charge, and we migration of many bird species return to Germany, display their encourage you to forward the file from Europe to Africa and back. A spectacular flight in our summer to anyone you think might share Wood Warbler, for skies, again migrate our enthusiasm for bird migration example, weighing to Africa and back and might be interested in this only ten grams, and for the first time publication. (the same weight build a nest and raise as ten paperclips) young. Two years We, along with the expert board flies from Britain from fledging to the of DER FALKE, hope that we to Ghana, often first brood, without have brought the phenomenon using exactly the touching the ground of bird migration closer to you same stopover sites once – as far as we with this extra issue. If you view in Burkina Faso, to know! Wood Warblers, Barn Swallows, winter in the same Wheatears, Cuckoos or Swifts group of trees as Common Cranes. Photo: H.-J. Fünfstück. In this special issue with slightly different eyes in the the year before. of DER FALKE, „Bird future and share our enthusiasm Barn Swallows from Europe jour- migration“, we wanted to explore for bird migration, then we have ney all the way to South Africa, bird migration in all its facets and achieved our objective. We hope thousands of kilometres over have pulled together input from you will enjoy this special issue of oceans, mountains and deserts – some of the finest experts on this DER FALKE. and return to exactly the same subject in Germany. To make the nest where they hatched the year content available to a wider audi- before. Swifts, born in Europe, ence, we have had it translated Best wishes

This PDF is a translation of DER FALKE special issue “Vogelzug”

We thank Nigel Agar, David Conlin, Caroline Donovan, Elke Schmidt and Alethea Wang for the translation of Dr. Norbert Schäffer Prof. Dr. Franz Bairlein texts into English. Chief Editor DER FALKE Director Institute of Avian Research “Vogelwarte Helgoland”

Science editors: Bank account: Wiesbadener Volksbank Imprint T. Brandt (tb), Dr. J. Dierschke (jd), BIC: WIBADE5W DER FALKE – Journal für Vogelbeobachter H.-J. Fünfstück (fü), Dr. W. Irsch (wir), IBAN: DE38 5109 0000 0015 1999 11 Dr. K. Richarz (ri), Dr. H. Stickroth (hs) ISSN 0323-357X, Copyright information: Dr. C. Sudfeldt (cs), Anita Schäffer www.falke-journal.de All articles published in this journal are Business adress: Editorial assistant: protected by copyright, which covers the !5,! 6ERLAG 'MB( s )NDUSTRIEPARK Dominique Conrad exclusive rights to reproduce the articles, 7IEBELSHEIM s 'ERMANY Tel.: 0049 6766/903-236; as well as all translation rights. Permis- Tel. 0049 6766/903-141, Fax: 0049 06766/903-341; sions for reproduction have to be con- Fax 0049 6766/903-320 E-Mail: [email protected] firmed in writing. No material published in this journal may be reproduced E-Mail: [email protected] Typesetting/composition AULA-Verlag: photographically, stored on microfilm or Editorial board: Rolf Heisler, Julia Schiwek reproduced in other ways without first Dr. Norbert Schäffer (chief editor; sch), Sales department: obtaining written permission from the E-Mail: [email protected] Britta Knapp publisher. Georg Grothe, Phone: 0049 6766/903-206 E-Mail: [email protected] Fax: 0049 6766/903-320 E-Mail: [email protected] Contents Bird migration

Norbert Schäffer, Franz Bairlein: Editorial

Franz Bairlein: The fascination of bird migration ...... 2

Nele Lefeldt, Susanne Schwarze, Henrik Mouritsen: Migratory bird orientation: 10,000 miles without TomTom®? ...... 12

Jochen Dierschke: Cartographic presentation of ringing data: German ring recovery atlas ...... 16

Klaus-Michael Exo, Wolfgang Fiedler, Martin Wikelski: On the way to new methods: A lifetime of round the clock monitoring ...... 20

Michael Wink: „Out of Africa“: The evolution of bird migration ...... 26

Susanne Homma: Training and ProRing e. V.: Support for voluntary bird ringing ...... 31

Olaf Geiter, Franz Bairlein: Colour-ringing – it‘s up to all of us ...... 32

Wolfgang Fiedler: Ringers, ringing centres, EURING and the future ...... 34

Hans-Günther Bauer: The Red List of migratory bird species ...... 36

Norbert Schäffer: Migratory bird conservation through international conventions ...... 40

Heiko Schmaljohann: Stopover ecology: What do migratory birds do when they rest en route? ...... 42

Volker Salewski: Migratory birds in Africa ...... 48

Martin Flade, Johannes Schwarz, Sven Trautmann: Long-distance migrants live more dangerously: Population trends of German migratory birds ...... 54

Ommo Hüppop, Kathrin Hüppop: Migratory birds and climate change: From long- to mid-distance migrant? ...... 58

Ralf Aumüller, Katrin Hill, Reinhold Hill: Offshore wind energy turbines: Possible effects of offshore wind energy turbines on bird migration ...... 62

Peter Südbeck, Gundolf Reichert, Petra Potel: Migratory birds and their conservation in the UNESCO – World Heritage Site Wadden Sea ...... 66

Johannes Wahl, Christopher König, Stefan Stübing: How can ornitho.de contribute to bird migration research? ...... 70

Der Falke 60, 2013 1 Bird migration

The fascination of bird migration The annual migration of millions of birds is one of nature’s most fascinating spectacles. How do we ﬁnd out about the migration routes and winter quarters of these birds; how do the birds know the right time to leave on migration, what their destination is, and how to ﬁnd their route; and how do they manage to survive the journey of thousands of kilometres and the crossing of deserts and oceans? These, and many other questions, have occupied natural scientists for centuries.

arl von Linné (1707-1778), in its neck, provided an indication of 120 million ringed birds), we have his Migrationies Avium pub- where it had spent the winter, as did reasonably good information on the Clished in 1757, still assumed the first ringing of White Storks and migration behaviour of many species that migrant birds hibernated at Woodcocks in the 19th century with (see pp. 16–19). the bottom of water bodies. Even recoveries in Southern Europe; but The great success of scientific ring- Heinrich Gätke, who painstakingly it was only in 1899, when the Dan- ing is due to the numerous voluntary recorded which bird species migrated ish teacher Hans Christian Mortensen helpers who carry it out in their free through Helgoland and when, was had the idea of fitting birds with time. There are some 800 volun- only able to speculate on their origin, small metal rings engraved with an teers in Germany and some 8,600 and where they went to in winter, in individual number and address, that in Europe as a whole. The existence his book The Helgoland Bird Observa- it became possible to shed some light of such a large voluntary effort is tory Ornithological Station published on the migration routes and winter- a unique phenomenon in zoologi- in 1891. The famous female ‘Arrow ing areas of birds. Today, after a good cal research throughout the world. Stork’, which was shot in 1822 near 100 years of bird ringing (within Ger- Most of the ringers now participate Wismar, N Germany, with an arrow many alone more than 20 million, in special programmes, where very of East African origin embedded in and throughout Europe more than specific questions are worked on, and which are coordinated on a national or European level. Information on the recovery of a ringed bird usually reaches the responsible national ringing centre. Here, on the basis of the ring number, the date and place of ringing is established and both the finder and the ringer are informed of the ringing and ring recovery data. Birds like the Pied Flycatcher (below) There is also an intensive exchange of marked with rings with a combination of information between national ringing numbers and letters can be individually centres, as ring recovery information identified. Photos: R. Nagel very frequently comes from abroad. Today there is a ringing centre in almost every country in Europe. In most countries there is only one national ringing centre. In Germany however, for historical reasons, there are three. These are the Institute of Avian Research ‘Vogelwarte Helgo- land’ in Wilhelmshaven, the Hidden- see Ringing Centre in Greifswald and the Radolfzell Ornithological Station on Lake Constance (formerly the Ros- sitten Ornithological Station). Birds ignore political boundaries, so trans- national cooperation is essential. For this reason the national European The arrow, of African origin, in the female ‘Arrow Stork’ ringing centres came together in 1963 of Wismar supplied information on the probable wintering to form the co-ordinating organi- location of the bird. Photo: R. Kinzelbach. sation for European bird-ringing

2 Der Falke 60, 2013 schemes (EURING) and agreed to use a uniform computer code for ringing and ring recovery data and to include their data in a common database (see pp. 34–35). After more than 100 years of bird ringing in Germany the first common bird migration atlas is currently being produced. More than a million ring recoveries from birds ringed by the three German ringing centres, as well as more than 150,000 recoveries in Germany of birds ringed outside the country, allow for the first time a comprehensive record of the migration of bird species occurring in Germany (see pp. 16–19). New technology, such as satellite telemetry, GPS tracking, geo-location, or stable isotopes analysis, further extend this Hand-reared Garden Warblers can be used to demonstrate that there is a relationship potential and permit previously open between the length of the innate ‘zugunruhe’ and the distance to their winter quarters. questions to be answered in details Photo: F. Bairlein. that ringing alone cannot provide (see pp. 20–25). tropics is very different. They leave tion northwards. This, however, can- their breeding grounds in midsummer not be the case for birds that winter » Migration as a result of inner when environmental conditions are on the Equator as the number of day- drive still excellent. Similarly, they leave light hours there is almost constant their tropical wintering areas with throughout the year. Nonetheless Young geese, cranes, or storks follow such precise timing, despite more or they return yearly to their breeding their parents on migration. Young less constant environmental condi- grounds with such precision that they Common Redstarts on the other hand tions, that they return to their breed- are often termed ‘calendar birds’. migrate, as do most birds, alone and ing grounds on almost the exact date These birds must have their own, by night. How does a young redstart, every year. What triggers the migra- innate calendar that determines the or indeed a young cuckoo that does tion urge in those species? timing of their departure either in not even know its parents, know One possible trigger for this precise autumn, when they begin their first when it is time to begin migration, sequence of migration is the seasonal migration alone southwards, or in where its winter quarters are, and fluctuation in hours of daylight, the spring, on return migration to their which route to take to them? How ‘photoperiod’. It was suggested that breeding grounds. This possibility does it make its way? the decrease in daylight hours in sum- came to be confirmed experimentally, For a long time it was assumed that mer and autumn triggers migration by rearing young birds using tweez- bird migration was triggered directly southwards, and the increase in day- ers and subsequently keeping them by environmental factors. The mass light hours in spring triggers migra- in a cage under carefully control- winter migration of Common Buz- zards, Eurasian Jays and Chaffinches on the occurrence of cold fronts or after snowfall is an example. Mass return migration is also noticeable when warm air infiltration occurs in Central Europe in spring. Northern Lapwings can hold out in Central France until they are able to exploit favourable climatic conditions and migrate rapidly into their Central European breeding grounds. However, the situation of long- range migrants that winter in the

Migration routes (schematic) of Northern Wheatears marked with geologgers.

Der Falke 60, 2013 3 Bird migration

led conditions with the same length in the wild of daylight, ambient temperature, autumn migration spring humidity, and food. Under such conditions they demonstrate the same migratory behaviour as in the wild. laboratory They are only nocturnally active in conditions their cage, as a manifestation of their nightly migration, when they would normally migrate in the wild. They demonstrate their nocturnal urge to migrate only during their species- speciﬁc migration periods. zugunruhe This urge to migrate or ‘zugunruhe’ continues over the several weeks dur- June Aug. Oct. Dec. Feb. April June ing which the birds would normally Schematic depiction of the migratory behaviour of Garden Warblers in the wild and migrate to Africa. Subsequently the under control conditions. birds are inactive for several weeks until the nocturnal ‘zugunruhe’ resumes in spring when the bird deter- 5000 km mines it is time for its return migration. We know today that numerous migrant bird species possess such an inner annual calendar that ensures their preparedness for migration at 2500 km the correct time and that they start and end their migration at the right point in time. The degree of ‘zugunruhe’ that a Zugunruhe bird produces in a migratory sea- 250 km son also determines the distance the bird has to cover. Species that ‘Zugunruhe’ and migration distance of the Garden Warbler (red), Blackcap (orange) and migrate only short distances, such as Marmora’s Warbler (yellow) (after Berthold 2008). the Marmora’s Warbler on Sardinia

4 Der Falke 60, 2013 Starlings cover only relatively short distances on their migration to their South European wintering areas. Photo: R. Nagel. Fat is the fuel for migration. This fat is stored under the skin and is outwardly well visible on live birds. Left: a still quite lean Gar- den Warbler, not yet adequately equipped for a long flight. Right: a Garden Warbler with its migration fat, well prepared for the long journey. Photos: F. Bairlein. which only migrates as far as the They still however, need to know fat stored by a bird prior to the start North African mainland, demonstrate what the destination is and by which of a flight determines the flight dura- very little ‘zugunruhe’. Whereas our routes they might be able to reach it tion and thereby its distance. One indigenous Blackcap which winters (see pp. 12–15). of the most noticeable adaptations in Spain, displays considerably more to the migration behaviour of many - corresponding to its longer migra- » Fat is crucial species is therefore a marked fatten- tion route - but only half as much ing at migration time - the so-called as the Garden Warbler that migrates The energy costs of migration are migratory fat deposition. Some spe- twice that distance to West Africa. A immense. In particular, those species cies initially store only a small fat close relationship, as an expression that traverse large ecological barriers deposit, which is refreshed repeatedly of species-specific innate migratory such as oceans and deserts require at a series of stopover sites (refuelling behaviour, therefore exists between enormous energy reserves. Only a stations). In contrast other species the distances covered on migration few species, such as terns, can take store huge amounts of fat. Garden and the total level of ‘zugunruhe’ up food without appreciably inter- Warblers for example, weigh between exhibited in the cage. Inexperienced rupting their migration flight. Most 16 and 18 g before autumn migration young birds migrating alone for the species must ‘refuel’ with energy or in their African wintering areas. first time use this innate programme before attempting a further stage of At migration time however, in both to automatically arrive at their winter migration. autumn and spring, a body weight of quarters. They only need to fly for as The principal energy (fuel) source more than 37 g can be attained, more long as their in-built migration time for active flight during migration is than doubling their fat-free start- programme instructs them to, and so fat. Long flights without corresponding weight. This increase is prima- arrive precisely at their destination. ing fat reserves are impossible. The rily attributable to the forming of an extensive fat layer under the skin. in the wild The basis of the fat deposition is an innate predisposition. Even under autumn migration spring constant management conditions birds only put on fat at the time they would migrate in the wild. At the end laboratory of July young caged Garden Warblers 25 conditions become heavier in the same way as their conspecifics in the wild. As soon as the wild birds reach their optimal 20 weight, they begin their migration to winter quarters. The caged birds however, cannot work off their built- body weight (g) body weight up fat reserves in flight. Nonetheless 15 the time comes when the caged birds Oct. Dec. June Aug. Feb. April June also completely shed their excess fat. Garden Warblers store fat when in cages only when they would migrate in the wild. The This occurs at the latest when their short period of fat storage in spring corresponds to the more rapid course of migration. conspecifics arrive in their African

Der Falke 60, 2013 5 Bird migration

winter quarters. At the stage when and inherent. Offspring of mixed In this way they are able to increase the captive birds believe that they are pairs (i.e., those of an Icelandic and their net energy intake. More efficient in Africa, they are lean and put on a Norwegian parent) exhibit an inter- exploitation is very advantageous weight again only for return migra- mediate amount of fat deposit. for economic reasons. It reduces the tion in spring. Species that have effort expended on ‘expensive’ forag- very long migration flights, such as » Gaining fat - but how? ing and so increases the gain neces- the Garden Warbler, put on much sary for the build-up of fat deposits. more fat than short or mid-distance The occurrence of natural fat deposi- The physiological mechanisms that migrants like the Robin. Migratory tion in caged birds heralded a break- form the basis for such a change in birds therefore have an innate pro- through in research into the mecha- the efficiency of dietary exploitation gramme that determines for them nisms and strategy of fat deposition. are still widely unknown. It is how- both the timing and the amount of The exciting questions this raises ever, interesting that these results migratory fat deposition, indepen- include how these birds can gain so were achieved for birds kept in con- dent of other external factors. much fat in so short a time, what pre- stant conditions in captivity. It can On the other hand, new studies conditions for successful fat deposi- therefore be assumed that this sea- on Northern Wheatears show that tion must be fulfilled, how the birds sonal adaptation to the build-up of fat migratory distance alone does not know how heavy they are to discon- deposits at migration time is subject determine the build-up of fat depos- tinue weight gain, and how they lose to inner control, which ensures quite its; whether a large ecological barrier the fat again in such a short space of independent of external factors, that also has to be overcome without stop- time after the end of migration. These such migratory birds attain a timely over or refuelling is another deter- studies under controlled conditions corresponding physiological disposi- mining factor . Northern Wheatears are complemented by similar studies tion for migratory fat build-up. that breed in Alaska, winter in East in the field. Here we concentrate our In addition to increased appetite Africa after a migration route of some studies on the Northern Wheatear. and better dietary exploitation, many 15,000 km. In captivity however, they This is a long-distance migrant that species adjust their diet at migra- store a fat deposit only about half as winters in the Sahel zone of Africa tion time. Geese, for instance, select large as Icelandic Wheatears, which and which in Germany, for instance, particularly protein-rich grasses and only have to cover some 6,000 km as migrates in large numbers via Helgo- herbs. This seasonal dietary adjust- far as West Africa. In contrast to the land. It is a bird of the open coun- ment is particularly noticeable in Alaskan birds whose migration routes tryside and therefore easy to observe. many songbird species that predomi- are almost completely over land with Using bait it is also quite easy to lure nantly feed on insects in the breeding regular opportunities for stopover and it on to a weighing scale so that it season, but to a great extent consume refuelling, the Icelandic Wheatears can be weighed regularly without berries and fruit for fat deposition at must first fly over the Atlantic. This the necessity to continually trap it. migration time. In the autumn Medi- demonstrates that the amount of fat In this way we gain an insight into terranean stopover areas in particu- deposit stored is population-specific its stopover behaviour, which to date lar, but also prior to spring migra- was not possible for any other spe- tion from tropical Africa, berries and cies. Only through this combination fruit play a large role in the diet of 16,2 g 0% of studies in the field and in the la- migrant birds. Many species, such as boratory is it possible to identify the the Garden Warbler, then feed almost complete extent of the preconditions exclusively on berries and fruit, so 19,1 g for successful fat deposition, thereby that in Italian they are known as ‘fig- 5% creating the basis for effective con- eaters’. The importance of this fruit 18,9 g 16,8 g 6% servation measures. diet for migration time fat deposition 0% 18,9 g The migratory fat deposition occurs was initially unclear, especially as 6% very rapidly, with daily rates of fat fat gain from fruit appears paradoxi- 18,7 g 20,2 g 7% 19% build-up of more than 10% of the fat- cal. Berries and fruit are generally 19,1 g free body mass. At a suitable stopover considered to be low in energy and 5% site, Garden Warblers with a fat-free nutrient value. They contain a com- 19,5 g 4% body mass of some 15 g can put on as paratively high proportion of water 18,4 g much as 1.8 g of body weight daily. and in human dietetics play a large 3% 21,3 g 35% It was long thought that migratory role as a reduction diet for the over- birds only became fat simply because weight. Recent studies show however, 19,9 g 18% they ate more. Indeed, at this stage that fruit consumption by the Garden 17,6 g the appetite of migratory birds does Warbler is of very critical importance 4% increase enormously. So much fat for the build-up of fat deposits. 22,6 g 58% cannot however, be gained through In so-called ‘cafeteria’ experiments, food intake alone. Garden Warblers in which the birds are simultaneously also exploit food intake better than offered a free choice of different diets, Average body mass, and percentage of Garden Warblers with more than 22 g body mass, at various trapping sta- previously and use the fat content Garden Warblers always choose the tions during autumn migration. in their diet much more efficiently. most fat-rich feed. If at migration

6 Der Falke 60, 2013 time they are offered insects and fruit however, they chose the fruit prefer- entially. These migratory birds also demonstrate a ravenous appetite for fruit richer in fat, or more precisely vegetable fats. Vegetable fats are particularly rich in long-chain, polyun- saturated fatty acids. If Garden War- blers are fed with two different feed mixes that are identical in total fat content but which differ in the proportion of unsaturated fatty acids, they choose the mix with a higher proportion of fatty acids. If they are fed exclusively with feed that does not contain these fatty acids, they are unable to build up migratory fat deposits. Interestingly enough, the fuel fat of migrant birds, in contrast to many other animal fats, is made up of over 60% of these unsaturated veg- Although they are known to be insectivores, at migration time Garden Warblers prefer etable fatty acids. Some of these are to feed on fruit rich in unsaturated fats. Photo: H. Jegen. essential for the bird and can therefore only be absorbed through its diet. The These conclusions on the advan- in the Mediterranean area caught on significance of unsaturated fatty acids tages of fruit consumption at migra- fig trees. Birds with access to fruit- for the metabolism of the bird in flight tion time, derived from laboratory bearing fig trees were consistently has not yet been clarified. However, it studies, are also confirmed in field heavier and had a higher daily rate seems that it is particularly important studies. Birds on passage trapped of fat deposit build-up than those in for flight endurance. The feeding on on elderberry trees in autumn near areas without figs, despite an overall berries and fruit by birds at migration Budapest were significantly heavier similar and adequate availability of time is therefore an important adapta- and demonstrated a much stronger insects. European Robins in Mediter- tion to enable the build-up of a very fat deposition than birds elsewhere. ranean stopover areas with vegetables particular quality of fat. The same goes for birds on stopover rich in fat also showed a higher level

For most bird species successful migration is closely tied to the availability of suitable stopover sites, for instance the Wadden Sea for many millions of Arctic migratory birds. Photo: R. Nagel.

Der Falke 60, 2013 7 Bird migration

of fat deposition than those in other ally on migration by some 15 million is endangered. It has been shown areas. In addition, there is often a birds in order to prepare themselves for Arctic geese that birds departing close connection between fruit avail- for their flight to Africa in autumn underweight from their stopover sites ability and frequency of birds on pas- or in spring for the return to their in northwestern Europe in spring sage at stopover sites. The quality of Arctic breeding grounds. The indi- have much less breeding success than food at stopover sites therefore plays vidual migration routes vary from birds with normal weight. This applies a very decisive role in successful fat species to species. Species that make similarly to White Storks, which only gain, and thereby successful migra- numerous stops require relatively lit- breed successfully in our country if tion. tle fuel for their short flight stages, they are able to attain a suitable con- but correspondingly many diverse dition through nourishment in their » Rest periods are essential for stopover sites. This is very different distant African winter quarters. successful migration for species that cover vast distances Little is known about such funda- in a single flight or those that migrate mentals in the case of the majority of For most species, successful migra- through areas where a stopover with songbirds. Like many other species, tion is dependent on the availabil- refuelling is not possible. These spe- Garden Warblers migrate from Cen- ity of suitable stopover sites where cies need extensive fat deposition tral Europe to West Africa but also they can refuel to stock up their fat and they must be able to cope with from Eastern Europe to East Africa. reserves. In this respect it is essential the few, or indeed the only, suitable For birds migrating via the south- to know the location of these stop- existing stopover sites. Knowledge westerly route, the main fat deposi- over sites, how much fat the individ- of the migration strategy of individ- tion takes place in Northwest Africa, ual species require for their migra- ual species is therefore vital for the immediately prior to crossing the tion stages, and therefore the ideal planning of conservation strategies. Sahara. This is different for Garden distance between stopover sites. This The amount of fuel stored for such Warblers on the eastern route. They is particularly important as suitable flights is very precisely calculated. If must attain their autumn fat deposi- stopover sites are at a premium in an a ‘planned’ stopover site is no longer tion north of the Mediterranean. The increasingly changing countryside. available, such species usually have reason for this is that there are an Many Arctic wader species spend no possibility of diverting to another adequate number of stopover sites in the northern winter in Africa. For area. In such cases, but also when the Northwest Africa in the wide belt of these species, the Wadden Sea in the conditions for adequate fat deposition Mediterranean vegetation in north- southern North Sea is a unique hub are not fulfilled, continued migra- ern Algeria and Morocco along the of their migration. It is used annu- tion or indeed later breeding success northern fringe of the Sahara. In the

The critical stopover sites for many of the migratory birds that winter south of the Sahara are located in North Africa. Photo: F. Bairlein.

8 Der Falke 60, 2013 east, on the other hand, the desert extends as far as the Mediterranean south coast and precludes the possibility of fat deposition in this area. These birds must therefore refuel to the north of and before they cross the Mediterranean. In spring the opposite applies. At this time the first significant fat deposits must be built up at the southern fringe of the Sahara. These birds also need the chance to refuel their energy reserves expended in crossing the Sahara. Studies at an oasis on the fringe of the Sahara in southern Morocco show that the great majority of the small birds stopping there in spring would not be able to reach their northern breeding grounds without refuelling. This applies not only to songbirds. After crossing the Barn Swallows roosting in an Acacia bush in the Etosha National Park in Namibia. Photo: K.-H. Loske. Sahara, Montagu’s Harriers make a stopover of several weeks to prepare » Crossing the Sahara – but how? bird migration to tropical Africa was for their onward migration to their characterised by the assumption that breeding grounds in the north. Study Some 200 European bird species win- the Sahara is a completely inhospita- of the spatial and temporal progress ter south of the Sahara in tropical ble region for migratory birds, with- of fat deposit build-up in migratory Africa. They therefore have to cross out shade, food, or water and con- birds and identification of the neces- the Sahara twice a year on migra- sequently, without any possibility of sary refuelling stations, is therefore, tion, which confronts them with a stopover. It was therefore generally an important goal of current ecologi- barrier some 2,000 to 3,000 km in assumed that migratory birds tra- cal bird migration research. width. The previous conception of versed this ecological barrier in one

The Sahara is a vast ecological barrier for many northern birds that winter in tropical Africa. Photo: F. Bairlein.

Der Falke 60, 2013 9 Bird migration

single non-stop flight, beginning this all the numerous mountain and cliff day they too resume migration the stage of migration in autumn, north areas, serve as stopover sites. These following night. If however, the fat of the Mediterranean. More detailed resting birds, most of which still deposition from a single day’s forag- studies in Algeria, Egypt, and Mau- carry sufficient fat, have no need to ing is insufficient for them to fly a retania demonstrated however, that refuel. They simply require sufficient further migration stage they remain many migrant birds do not cross the shade, spending the hot daylight in the stopover site for as long as it Sahara in a single flight but rather in hours saving on energy and water takes to adequately build up the fat several stages, flying by night and expenditure. The following night deposit. resting by day. they resume migration. The passage A bird in flight expends not only a These studies showed, in contrast of such birds thus occurs rapidly and great deal of energy; its muscle activ- to previous assumptions, that migra- unobtrusively. ity also produces enormous amounts tory birds of various species observed The behaviour of the individu- of heat. This needs to be dissipated in in the desert were generously fat. als that land without sufficient fat order to avoid dangerous overheating These birds landed at dawn or dur- reserves to continue migration is of the body. Birds flying by day are ing the early morning, subsequently different. If such lean birds land in also warmed by solar radiation. Birds rested - mostly inactive and without a location without adequate food can only dissipate such heat by water feeding in the shade of vegetation availability they are unable to resume loss from the body, similar to human and rocks - and resumed migration migration. Nonetheless, it has been sweat. If no drinking water is avail- in the evening. Only a small propor- shown that these lean birds estimate able, the sole internal water source is tion of them stopped over for several the ‘quality’ of a site before landing oxidation water, created by chemical days and these were all quite lean. In and choose their stopover accord- depletion of fat. A bird on migration contrast to the fat birds, they foraged ingly. How they do this is unknown; thus requires its fat deposit not only actively during the stopover. They they probably estimate the amount for energy but also to act as its ‘water then resumed migration after they of food available from the amount of bottle’. However, only some 10% of had stocked up sufficiently on fat. visible vegetation. They usually land the extra heat can be dissipated by These data present a different pic- only in the larger oases rich in veg- this oxidation water. The remain- ture of the trans-Sahara migration of etation where it is likely that food can ing heat is dissipated at the cost of many migratory birds. Many of them be found. During the day they then the body water content. This means land in the Sahara after a night spent forage intensively. If they are able to increasing body dehydration for the on migration, where oases, but above adequately refuel in the course of the migrating bird. As birds can only tol-

The crevices in the mountain cliffs are favoured roosting sites for migratory birds in the Sahara. Photo: F. Bairlein.

10 Der Falke 60, 2013 erate a certain degree of dehydration not only applies to birds that have Prof Dr Franz Bairlein ob- without harm, the potential flight to cross the Sahara but also, for tained his doctorate at the duration or distance is dependent on instance, to Icelandic Wheatears that University of Konstanz, and what is now the Max Planck the ambient temperature. Long dis- build up their fat deposits on Helgo- Institute for Ornithology at tance flights are not possible in high land in spring for their long trans- Radolfzell, on the study of the stopover external temperatures as this would oceanic journey. ecology of migratory birds. Since 1990 he lead to a dangerous degree of dehy- Intact habitats are thus essential. has been Director of the Institute of Avian dration for the bird. but, in many places are endangered by Research – Vogelwarte Helgoland – in Wilhelmshaven. His research focus is bird A bird migrating across the desert destruction and degradation (see pp. migration. has two alternatives. First, it can xx and xx). At the same time migra- [email protected] select a flight height where it is tory birds are exposed to changes cooler. However, during trans-Sahara as a consequence of global climate Related literature: migrations at great heights, birds are change (see pp. xx to xx). Modern Alerstam T 2008: Avian Migration. often faced with headwinds. On ener- avian research in the field as well as Cambridge University Press, Cam- gy-saving grounds they must avoid in the laboratory, provides data in a bridge. these by losing height, as flying into number of ways that is not only fun- Bairlein F 1988: How do migratory headwinds costs too much energy. damentally necessary for identifica- songbirds cross the Sahara? Trends At lower heights the birds then have tion of the specific threat factors and in Ecology and Evolution 3: 191- following winds, but it is too hot for the planning of effective conserva- 194. Bairlein F 1998: Langstreckenwan- longer flights. Many migratory birds tion measures, but also contributes to derungen von Zugvögeln – energe- solve this conflict by migrating dur- our understanding of the way birds tische Meisterleistungen. Biologie in ing the cooler hours of darkness, rest- react to the varied anthropogenic unserer Zeit 28: 270-280. ing in the shade by day, resulting in a changes that confront them. In this Berthold P 2008: Vogelzug – eine good water balance. respect international cooperation is aktuelle Gesamtübersicht. Wis- The precondition for successful absolutely essential. Only in this way senschaftliche Buchgesellschaft, Darmstadt. migration is, in any case, that such can the full extent of species-specific Schmaljohann H, Liechti F, Bruderer birds possess adequate fat depos- threat factors be identified and from B 2007: Songbird migration across its, which they accrue by adequate there the necessary conservation the Sahara – the non-stop hypothesis nourishment in the stopover sites in measures planned and implemented. rejected! Proceeding of the Royal advance of ecological barriers. This Franz Bairlein Society of London B 274: 735-739.

Outdoor aviaries for captive breeding of Northern Wheatears at the Institute of Avian Research, Wilhelmshaven, Germany. Photo: R. Nagel.

Der Falke 60, 2013 11 Bird migration

Migratory bird orientation: 10,000 miles without TomTom®? Migratory birds cover thousands of kilometres around the globe, apparently effortlessly and equipped only with their own senses. In contrast, for us humans, in times before the development of modern aids,navigation was as tricky as it was risky. How do birds – with their ‘birdbrains’ – manage to navigate with so little effort?

fter more than 60 years’ of even motorways, as well as odours they spontaneously jumped and flut- intensive research it is now and perhaps even ultrasonics. tered in the direction that they would Aknown that birds have sev- have selected in the wild. Cross- eral reference systems (compasses) » Innate direction breeding experiments with Blackcaps that work simultaneously, and often demonstrated the heritability of this combine information from several Before we take a closer look at the innate directional behaviour. If birds cues to find their way to the desired individual navigation systems, the from populations that migrate to the destination. Whether a pigeon wants question arises as to how a bird knows west of the Alps were crossbred with to return to its loft, a Robin flies to at all when it must begin migration those that take an easterly migra- winter in Spain, or an Arctic Tern cir- and to where. Information on this was tion route, their offspring selected a cumnavigates the globe, they can all provided by studies on warblers in southerly migration direction exactly make use of the sun, the stars, and the 1970s and 1980s. Young warblers, between the migratory directions of the Earth’s magnetic field as naviga- which had never migrated themselves, the two parental populations. If birds tion aids. Additionally, some species were kept in captivity. Their spontane- from non-migratory populations were can also navigate using landmarks ous choice of migration direction was crossbred with long-distance migrant such as large rivers, mountains, or studied in cages, and it turned out that populations of the same species, the

Together with the bird‘s inner clock, the sun is used by day migrants as the most important compass reference. Information received at sunset can also play an important role for nocturnal migrants, e.g. to calibrate the magnetic compass. Photo: H. Glader.

12 Der Falke 60, 2013 magnetic !eld lines magnetic N North Pole

~ 60000 nT

angle of inclination magnetic Equator Equator

~ 30000 nT

S magnetic South Pole

~ 60000 nT

Schematic depiction of the Earth‘s magnetic field. The Earth‘s magnetic field is strongest at the magnetic North and South Poles (c. 60,000 nanotesla) and the field lines there are perpendicular to the Earth‘s surface. When one moves towards the magnetic Equator, the strength of the magnetic field, and the angle between the magnetic field lines and the Earth‘s surface, decrease successively. The angle of inclination and the strength of the magnetic field can thereby be used to determine the rough north-south position and, because the magnetic field lines always point to the magnetic north, the Earth‘s magnetic field can also be used as a compass. offspring became middle-distance unmentioned, since some bird species the birds later orientated themselves migrants. appear to calibrate their magnetic on this. In other words, the strategy compass by the polarisation pattern of young birds manifests as a search » How migratory birds navigate of the setting sun. But what happens when Because migrant birds kept in captiv- the sun cannot be used as ity attempt to migrate in their spe- a reference system,e.g. cies-specific migration direction dur- at night? Do birds have ing the natural migration season, this a sextant in their brains behaviour can be used to discover and orientate themselves what information the bird requires for on the Pole Star as sea- orientation. Gustav Kramer, a con- men have for centuries? temporary of Karl von Frisch, used Emlen&Emlen tested mirrors to demonstrate that Common night-migratory birds in Starlings can use the sun for orien- a planetarium and dem- tation. It was later discovered that onstrated that they can the determining factor was not the use information from the sun’s height above the horizon, but starry sky as a compass rather the azimuth (the sun’s angle and that a functional star as projected on the horizon). It was compass requires learn- also discovered that orientation using ing of the starry sky’s the sun is learnt in an early imprint- centre of rotation. When During the migratory season, the orientation behav- ing phase and has to be synchronised Emlen&Emlen exposed iour of birds is tested in so-called Emlen funnels. with the circadian rhythm, i.e. the hand-reared young birds Their migration urge is so strong that they jump in bird’s inner clock. The possible role of to a ‘false’ centre of rota- the preferred direction, thereby leaving scratches on polarised light should also not be left tion in the planetarium the paper lining of the funnel for later analysis.

Der Falke 60, 2013 13 Bird migration

rear

cerebellum Cluster N cerebrum

magnetic magnetic mid- compass compass hind- brain brain front spinal-cord from the eye

Schematic depiction of a Robin’s brain. We know at present that magnetic compass information is processed in the areas marked in red. (Cluster N in the forebrain and part of the visual area of the thalamus in the midbrain). Modiﬁed version of Mouritsen et al. 2005: Night Vision Brain Area in Migratory Songbirds. PNAS 102, 8339-8344..

for rotating points of light in the sky » Magnetic sense is the angle between the Earth’s sur- and interpreting the centre of rota- face and the magnetic field lines, i.e. tion as north. The Earth’s magnetic field is defined the inclination angle of the Earth’s Likewise, what happens on over- by three parameters: direction, inten- magnetic field to the horizontal. It cast days? In order to answer this sity and inclination. The direction of has a value of 0° (horizontal to the question, researchers have investi- the magnetic field always points to Earth’s surface) at the magnetic gated the most difficult to understand the magnetic North Pole. The inten- Equator, ca. 65° in Central Europe and yet most fascinating orientation sity or strength of the magnetic and 90° (perpendicular to the Earth’s system – the magnetic sense. Wolf- field can almost be read like a map. surface) at the magnetic poles. In gang Wiltschko was the first to show It is relatively linear from 30 000 nT this way, the Earth’s magnetic field that migratory birds use the Earth’s (nanotesla: unit of measurement for potentially provides a bird with a magnetic field for orientation. How the strength of the magnetic field) at useful map as well as compass infor- exactly do birds sense the Earth’s the magnetic Equator and increases mation. But how can this informa- magnetic field? Here we arrive at a to 60 000 nT at the magnetic poles. tion be perceived and processed in a question that is considered to be one It thus provides a potentially usable ‘birdbrain’? of the last remaining fundamental pattern, although anomalies do occur At present there are three hypothe- riddles in sensory biology. worldwide. The magnetic inclination ses on the perception of the magnetic field. The first and oldest hypothesis assumes that small structures similar to a compass needle exist in birds’ bodies. These could be in the form (1) of small iron oxide (Fe3O4 - magnet- ite) crystals. The second hypothesis (2) proposes that the magnetic field is perceived by the bird’s eye, in which Zvenigorod there are molecules whose photosensi- tivity are dependent on the alignment 1000 km Rybachy of the magnetic field relative to the molecule, and could therefore enable the bird to ‘see’ the Earth’s magnetic field. The third hypothesis proposes that the lagena, part of the sense of balance in the inner ear, is responsible for the perception of the magnetic field. But which hypothesis(es) Eurasian Reed Warblers were relocated from Rybachy to Zveningorod in Russia, a dis- is/are correct? At present it appears tance of ca. 1,000 km. Birds that cannot transfer magnetic information through the that birds have a magnetic compass trigeminal nerve (1) do not notice the relocation. Untreated birds can however compen- in the eyes and a magnetic map sense sate for the relocation (2) in their upper mandible.

14 Der Falke 60, 2013 The possibility of a magnetic com- » Compass and map navigation devices and even for the pass in birds’ eyes was first concluded development of quantum comput- when Robins tested in Emlen funnels In order for true navigation to take ers. for their migratory behaviour were place, a map is required in addition Nele Lefeldt, Susanne Schwarze, discovered to be capable of using to a compass. It is therefore possi- Henrik Mouritsen only light with specific wavelengths ble that birds receive magnetic map Institute for Biology and Environmental (colours) for compass orientation. The information with the help of other Sciences, Oldenburg University birds could orient well in blue and magnetic sensors. Indeed,scientists green light but became disorientated believethey discovered iron mineral in yellow and red light. This would be structures associated with nerve tis- Related literature: difficult to explain if the eyes were sue in the upper mandible that were Alerstam T 2008: Avian Migration. not in some way involved in the per- suspected to act as magnetic sensors Cambridge University Press. Berthold P 2011: Vogelzug: Eine aktu- ception of the magnetic field. for map information. Closer exami- elle Gesamtübersicht.Wissenschaft- A theoretical model was then devel- nation however, revealed that the liche Buchgesellschaft. oped as a potential explanation, sug- iron mineral structures were actu- Emlen ST 1975: The Stellar-Orientation gesting that absorption of short wave- ally cells of the immune system. System of a Migratory Bird. Scientific length light by molecules present in Nonetheless, experiments since have American August 1975: 102-111. the eye creates radical pairs (unpaired shown that the nerve that transfers Kishkinev D, Chernetsov N, Heyers D, Mouritsen H 2013: Migratory electrons) that are sensitive to the information from the upper mandi- Reed Warblers need intact trigemi- magnetic field. These molecules can ble to the brain perceives magnetic nal nerves to correct for a 1,000 km exist in two different quantum condi- information. In Robins, the two eastward displacement. PLoS ONE tions following a quantum chemical brain areas receiving information 8(6): e65847. doi:10.1371/journal. light reaction. Depending on how the through the ophthalmic branch of pone.0065847. molecule is arranged relative to the the trigeminal nerve contain a large Mouritsen H, Hore PJ 2012: The Earth’s magnetic field, both compo- number of neurons, which are acti- magnetic retina: light-dependent and trigeminal magnetoreception in nents have a different yield. As these vated by magnetic field changes. migratory birds. Current Opinion in molecules appear to be distributed Furthermore, Eurasian Reed War- Neurobiology 22: 343-352. equally across the whole of the hemi- blers indigenous to Russia lacking Wiltschko R, Wiltschko W 1999: Das spherical retina, the result is probably intact trigeminal nerves, were unable Orientierungssystem der Vögel I-IV. a sort of pattern that can be under- to compensate for an east-west relo- Journal für Ornithologie 140: 1-40, stood as a visual impression of the cation during spring migration; and 129-164, 273-308, 393-417. Zapka M, Heyers D, Hein CM, Engels magnetic field, and this could provide pigeons with cut trigeminal nerves, S, Schneider NL, Hans J, Weiler S, birds with compass information as a trained to recognise a specific mag- Dreyer D, Kishkinev D, Wild JM, kind of heads-up display. But does netic field, could no longer solve this Mouritsen H 2009: Visual but not the eye contain such molecules? task. The upper mandible therefore trigeminal mediation of magnetic In 2004, the sole class of recep- appears to play a part in the per- compass information in a migratory tor molecules that seem to meet all ception of magnetic map informa- bird. Nature 461: 1274-1277. requirements, the cryptochromes, tion. The primary receptors however were proven to exist in the retina of remain undiscovered. Nele Lefeldt is a graduate student in Prof Dr migratory birds. In addition, it was The third hypothesis involving Mouritsen‘s working group demonstrated that the expression, the lagena has only been proposed ‚Animal Navigation‘ on i.e. the production, of cryptochrome recently. American scientists dis- the orientation of migra- significantly increases in the cells of covered that the parts of the bird’s tory birds using the earth‘s the retina of migratory birds such as brain that receive information from magnetic field. Her current project is concerned with the role of the lagena in the Garden Warbler or Robin at night the lagena react to magnetic field magnetic field orientation. when they display migratory behav- impulses. It still has to be clarified [email protected] iour. It was also shown that Garden what implication this has for the Susanne Schwarze is also Warbler cryptochromes form very magnetic field orientation of birds. It a graduate student in Prof long-lived radical pairs when they should be stressed that at the current Dr Mouritsen‘s working are exposed to light. point in time, none of these theo- group. She works on the The related processing areas in the ries exclude each other in any way influence of electromagnetic interference frequencies on bird’s brain have also been identi- and a combination of the individual the orientation behaviour of nocturnal fied. A small part of the thalamofugal hypotheses is quite conceivable. migratory birds. pathway in the bird’s brain is respon- Despite all efforts by man to Prof Dr Henrik Mouritsen sible for processing magnetic com- understand the fascinating naviga- has directed the ‚Neurosen- pass information. It is therefore relation capabilities of migratory birds, sory/Animal Navigation‘ tively certain to date that the mag- there are still many unsolved rid- working group at Olden- burg University since 2002. netic compass of migratory songbirds dles that we want to decode in the He is primarily interested in is located in the eye and that birds coming decades. It is likely that the understanding the orientation mechanisms have a visual perception of magnetic discovered mechanisms will pro- of migratory birds and how they sense the field lines. vide inspiration for new man-made Earth‘s magnetic field.

Der Falke 60, 2013 15 Bird migration

Cartographic presentation of ringing data: German ring recovery atlas

Birds have been fitted with rings in Germany and Europe for over 100 years. The results of this scientific bird ringing have been included in numerous publications on bird migration, but a comprehensive presentation of the ring recoveries for the whole of Germany has been lacking to date- this gap will now be filled.

he introduction of scientific bird ringing more than T100 years ago revolutionised avian research. For the first time it became possible to establish the location of individual birds outside their breeding areas, as well as their migration routes and wintering areas. The first ring recovery atlas published by Schüz & Weigold in 1931 brought sensational information, for instance, the wintering of European Barn Swallows 10,000 km distant in South Africa. Since then some 20 million birds have been ringed in Germany with more than a million ring recovery reports. In addition there have also been some 150,000 ring recoveries in Germany of birds ringed abroad. A German ring recovery atlas was therefore overdue, especially because various

Winter recoveries of ringed Stock Doves breeding in Germany are reported primarily from South-western Europe. Some breeding birds of the North-western German Plain (above left) winter however in the Benelux states. The inset maps show the major natural regions in Germany from which the recovered birds originate. Photo: J. Dierschke.

16 Der Falke 60, 2013 other national ring recovery atlases have been published recently - as in the Czech Republic, Denmark, Fin- land, Italy, Norway, Sweden, and the United Kingdom.

» A long way Evaluation of the movement of breeding birds, on stopover or wintering in Germany, began several years ago. For historical reasons, there are three ringing centres in Germany (Helgoland, Hiddensee and Radolfzell) each with its own data system and data structure. Before a common ring recovery atlas could be produced, several details thus needed to be addressed. First, the different databases had to be combined. Second, a comprehensive check for errors in the data had to be completed. The database also had to be extended to include undigi- taliseddata, data on recoveries in Germany of birds ringed abroad listed in the EURING database, and data from colour ring projects. As these projects are mostly organised The autumn migration of the Common Swift is in a southerly or south-westerly direc- by ringers themselves, consultation tion. The few ring recoveries from south of the Sahara indicate a possible wintering with their coordinators was neces- area in Central Africa. Photo: C. Moning. sary to acquire the data. More specialised tracking data from satellite telemetry, GPS telemetry, or geolocation (see pp. 20 to 25) were not included in the combined database. However, they were used in the species notes if they aug- mented the ring recovery data and were published or freely available (e.g. in MoveBank https://www.movebank.org/).

» Many questions Ringing recoveries can throw light on a number of scientiﬁc issues. However, in orderto produce a compact, single volume work, it became evident that a German ring recovery atlas must be restricted to just a few questions. The scope of the atlas is therefore limited to the following questions: s (OW LARGE IS THE DISTRIBUTION RANGE of birds occurring in Germany? s 7HICH MIGRATION ROUTES DO BIRDS occurring in Germany take? s 7HERE DO BIRDS THAT BREED IN 'ER- many spend the winter?

Der Falke 60, 2013 17 Bird migration

s 7HERE ARE THE BREEDING GROUNDS OF birds that winter in Germany?

» Evaluation The number of ringing recoveries differs considerably between species. In some cases very few recoveries have been received, even for common species like the Turtle Dove and Woodlark. For others, the database is almost overﬂowing with recoveries, e.g. Barn Owl, White Stork, and Starling. It was therefore decided not to treat all species equally but to present species with large numbers of ring recoveries on two or four pages, species with few recoveries on a single page, and species with only single recoveries in a short text or in tabular form. Only those ring recoveries with a distance of more than 10 km between ringing and recovery locations were considered. In order to highlight geographical differences in migratory behaviour of birds ringed in Germany, the recoveries are depicted with a colour-coded relationship Most ring recoveries of Reed Warblers have been made on a north-east to south-west indicating their area of origin. This axis. There are however, some recoveries in a south-easterly direction, indeed as far as South-east Africa and therefore considerably further south than those on the south- is based on the major natural regions westerly route. Dots: ring recoveries, stars: ringing locations of birds with a foreign ring of Germany (see http://en.wikipedia. recovered in Germany. Photo: C. Moning. org/wiki/Natural_regions_of_Germany). This makes it easy to determine, for instance, whether birds of Eastern Germany spend the winter in different areas to those of Western Ger- many.

» First results Data for some species has been eval- uated and presented in cartographic form. Here are a few examples: s 3TOCK $OVES THROUGHOUT 'ERMANY migrate in a south-westerly direction to winter in Portugal and south-west Spain. Birds that winter in the Benelux states, however, come exclusively from North-west Germany. An exception was a Stock Dove ringed on 28.7.1984 in Northern Württemberg that was shot in January 1985 in Turkey. s -OST #OMMON 3WIFTS MIGRATE IN a south to south-westerly direction. There have only been very few ring recoveries south of the Sahara, but these indicate that the species’ wintering area is in Cen- tral Africa.

18 Der Falke 60, 2013 s 4HE MAJORITY OF 2EED 7ARBLERS ringed in Germany migrate in a south-westerly direction to winter in West Africa between Guinea and Nigeria. A number of birds, however, migrate to the south-east and southwards as far as South- east Africa.

» Outlook This ﬁrst ever evaluation of the complete ring recovery data from the whole of Germany will provide a great deal of information, some of it new and surprising. A number of matters cannot, however, be presented in such a compact atlas. These will require more special Autumn migration of the Ring Ouzel through Germany. There are a few recoveries of treatment that we explicitly wish to Scandinavian birds on passage but none however, from the German breeding popula- encourage. On the other hand it will tion. The unbroken lines denote ring recoveries in the months immediately following become evident for which species we ringing. Red dot: Helgoland. Photo: J. Dierschke. have little or no information about their migration routes. For instance, although there are quite a few ringing recoveries of Scandinavian Ring Ouzels in Germany, we have no data on the migration routes and wintering areas of Ring Ouzels breeding in Germany, as there have been to date no recoveries of the very few Ger- man breeding birds that have been ringed. It would therefore pay off to ring more birds of this species. By exposing such gaps in our knowledge we hope to encourage our numerous voluntary ringers to ﬁll these gaps wherever ringing makes this possible. Finally, we would like to thank the countless voluntary ringers who have ringed birds over the past 100 years, tirelessly and often with a high level of personal commitment, thereby making an invaluable contribution to migratory bird research. Jochen Dierschke, in cooperation with Volker Dierschke, Wolfgang Fiedler, Olaf Geiter, Kathrin Hüppop, Ulrich Köppen, Volker Salewski and Franz Bairlein.

Dr. Jochen Dierschke is Related literature technical Head of the North Heinicke T, Köppen U 2007: Vogelzug in Ostdeutschland. I. Wasservögel, Teil 1. Ber. Sea ﬁeld station of the In- Vogelwarte Hiddensee 18 (SH), Greifswald. stitute of Avian Research Schüz E, Weigold H 1931: Atlas des Vogelzuges. R. Friedländer & Sohn, Berlin. ‚Vogelwarte Helgoland‘ and Zink G 1973, 1975, 1981, 1985: Der Zug europäischer Singvögel: ein Atlas der Wie- member of the specialist editorial board of derfunde beringter Vögel. Lfg. 1-4. AULA-Verlag, Wiesbaden. DER FALKE. Zink G, Bairlein F 1995: Der Zug europäischer Singvögel: ein Atlas der Wiederfunde [email protected] beringter Vögel. Vol. 3. AULA-Verlag.

Der Falke 60, 2013 19 Bird migration

On the way to new methods: A lifetime of round the clock monitoring Bird migration has been studied both by visual observation and by ringing studies. This has enabled the general location of breeding, stopover and wintering areas of many species to be identified. As a rule, ringing studies determine only two points, the ringing and the recovery point. The introduction of satellite telemetry in the mid-1980s permitted a more or less continuous tracking of individuals for the first time and thereby provided an analysis of all regions visited in the course of a year. Because of transmitter size, the use of this technology was for a long time restricted to a few large bird species. Today a variety of further methods are available that also permit the tracking of small birds, as well as the parallel recording of different behaviour forms and environmental parameters in high spatial and temporal definition. In future, the combination of established and newly developed methods will enable birds of almost all sizes to be studied during their complete lifespan.

atellite telemetry has revolu- of a bird’s journey, they also provide mitter, weighing at that time 170 g, tionised the research of bird information on where and for how a so-called PTT (Platform Transmit- Smigration. Comprehensive long it stops over, where it winters, ter Terminal). Since that time satel- individual-based analyses of habitats and whether it wanders around or is lite telemetry has developed rapidly. throughout the year became possible tied to a specific area in the winter- Whereas transmitters in the mid- for the first time, often for several ing period. 1980s still weighed over 150 g and years in succession. Regular fixes For the first time in 1984 a Bald could only be worn by a few bird permit not only the direct following Eagle was fitted with a satellite trans- species, such as large birds of prey,

24 x 14 x 7,5 mm

One of the lightest currently available standard solar-powered satellite transmitters weighing only ﬁve grams. Photo: R. Nagel, IfV.

The migration routes of the male Montagu’s Harrier, ‘Franz’ - born 2001 in Reiderland and ﬁtted with a satellite transmitter in 2006 - were recorded for over ﬁve years. The bird wintered regularly in South Mau- retania/North Mali. Photo: T. van Kooten.

20 Der Falke 60, 2013 storks, geese, and swans, by the year autumn migration spring migration 2000 similar transmitters weighed only 18 g. Since 2008 standard solar transmitters weighing only just 5 g are available, so that now species with a body mass of some 150 g can be marked, for instance, the Hobby and Amur Falcon, Cuckoo, or Grey Plover. In spring 2012, Microwave Telemetry System Inc., presented the prototype of a solar PTT weighing only 3.2 g. Solar powered satellite transmitters permit many fixes over a number of years. In addition to high performance transmitters, ARGOS receivers in satellites are at the core of satellite telemetry. The satellites used by ARGOS (NOAA- und MetOp/ Eumetsat satellites) circle the earth at a height of about 850 km. Until 2001 fixes were obtained exclusively 0 1000 2000 by means of the Doppler Effect and km were consequently relatively impre- Autumn and spring migration routes of male (blue) and female (red) Montagu’s Harriers recorded cise. As a rule, an accuracy of more using satellite telemetry. It is clear that most birds select the same routes for autumn and spring than a few kilometres and often even migration. They kept mainly to the first chosen route for many years. several dozen kilometres could be achieved. This level of accuracy was there are no ring recoveries to date is known to all mobile phone users. adequate for the analysis of migra- and are unlikely to be in future. Indi- As well as monitoring of persons it tion routes and the regions visited vidually based data from all habitats can also be used to locate wildlife. in the course of a year, even though used in the course of a year are not When fitted with additional sensors, - particularly in Europe - this tech- only of paramount importance for an a number of further parameters as nology often provided very modest understanding of bird migration but well as three-dimensional location results. Since the turn of the century, also provide information of imme- data can be transmitted to the mobile solar powered GPS (Global Posi- diate relevance to conservation. The phone of the observer or direct to an tioning System) supported satellite disadvantages remaining include the Internet database. In contrast to sat- transmitters became available. These still quite heavy weight of GPS trans- ellite telemetry, it is possible to com- transmitters provide spatially high- mitters of some 20 g, the high power municate with the transmitter on the definition three-dimensional data consumption necessary to transmit back of the bird, in order to turn it using the GPS system to determine the data in orbits at an altitude of on or off or to alter the data record- their position and transmitting this about 850 km, the comparatively low ing rate. The great advantages of the data via satellite. The high spatial number of possible daily fixes (at best GSM network are its wide coverage definition (accurate to < 5 m) per- 10 – 20), and the high costs for data and simple use. On the other hand the mits, for example, the localisation of transfer and the transmitter com- available devices are still compara- breeding and stopover sites so that pared to the sobering high technical tively heavy due to the high power they can be visited for more detailed failure rates. consumption of its necessary power- studies. In addition, GPS transmit- ful buffer battery (GSM / solar GPS ters can be fitted with other sensors » Long distance transmission via 20 – 70 g). such as accelerometers, pressure mobile communications (GSM) Specific high frequency transceivers and temperature sensors, or physi- permit the use of considerably lighter ological measuring devices, so that At present, less expensive micro- transmitters weighing only some 6 g, a completely new quality is achieved processor-controlled GPS loggers are but do not permit use of the mobile in bird migration study. The lightest gaining in importance. These data network and therefore require the of the currently available solar pow- loggers are capable of storing more installation of special reception sys- ered GPS transmitters weighs some than 10,000 fixes and the data can be tems or the use of handheld receiv- 20 g. acquired over several kilometres using ers. In dense woodland their range is The great advantage of satellite the GSM (Global System for Mobile often less than 300 m while in open telemetry is that data on rare species Communication) mobile communi- countryside up to several kilometres can also be collected in a short space cations system or UHF/VHF receiv- can be achieved. of time even from the most remote ers. GSM is the standard for digital The fix, accurate to a few metres, regions, including areas from which mobile communication networks and can be stored at intervals of seconds

Der Falke 60, 2013 21 Bird migration

provided an adequate power supply lems. The use of ‘intelligent’ switch- data are either stored for a migration and storage capacity is available. ing of the logger, which, dependent season, a year, or very occasionally The latter is impressively high. Even on the power supply, can temporarily even longer. In contrast to telemetry the smallest logger can store up to pause certain activities and resume the birds are not tracked in real time; 320,000 fixes. This means that, in the them at the appropriate time, can they have to be recaptured in order to case of species with high site fidelity, deal with these problems. Purely noc- read the data or to remove the geolo- the data can be read after the return turnally active birds and bats present cator. The method is therefore suit- of the birds from winter quarters to these systems with additional but not able in the first instance for species breeding site. Because of the great insoluble problems, as long datasets with breeding or birthplace fidelity. precision and high data density, the from Eagle Owls and the first results After recapture the data are read with new generation of data loggers per- from fruitbats demonstrate. the times of midday and midnight mit both a detailed analysis of the providing the geographic longitude, migration routes and stopovers in » Light-level geolocation and the length of daylight and hours various habitats, as well as the locali- of darkness providing the geographic sation of roost and feeding trees and The methods presented above are latitude. Each day therefore two fixes nests, even when these are many unsuitable for analysis of the migra- with an accuracy of some 150 km thousands of kilometres distant from tion routes of birds weighing less than can be determined. This degree of the observer. 150 g. This means that up to about accuracy is adequate to establish the The rapid availability and high pre- 10 years ago no suitable method was locations of the migration routes and cision of the data enable a number available for most species - includ- the winter quarters of mid- and long- of further analyses, e.g. merging ing all songbirds. The breakthrough distance migrants. with environmental parameters such occurred with the use of light-level The imprecision in the determina- as the current weather conditions geolocators, which have helped tion of sunrise and sunset means that or data on land use. Waypoints can clarify the migration routes of many for 10 – 14 days either side of the also be transmitted to the autopilot species, e.g. Blackbirds, Wheatears, equinoxes it is impossible to reliably of a small, unmanned aircraft that it Hoopoes, Swifts, and Turnstones. The determine the exact latitude. Deter- can then retrace the routes and pho- lightest geolocator at present weighs mination of the times of sunrise and tographically record the land use. only 0.6 g, so that birds weighing as sunset, and with them the calculation These loggers enable a data density little as 12 – 15 g can be fitted with of the latitude, can be difficult when that was inconceivable only a few them. The central components are a the species roosts in woodland or reed decades ago and which makes new photocell, a clock generator, a small beds, or even withdraws for the night demands of methodology on the part computer, a memory, and a battery. into a cave or other dark refuge. The of analysts. The light-level geolocation prin- screening of the sun causes sunset to Solar-powered satellite transmitters ciple is quite simple and age-old. appear earlier and sunrise later than and GPS loggers permit continuous It was used in the Middle Ages by is indeed the fact. The logger should recording over several years. In Cen- mariners to determine their position. therefore be calibrated in advance in tral Europe the comparatively short Using a photocell, geolocators record the appropriate habitat. daylight periods in winter and the the intensity of the incident light weaker irradiation can cause prob- together with date and time. These » ICARUS We expect the next revolution in migratory bird and behavioural research to be round-the-clock observation of wildlife from space. The ICARUS project (International Cooperation for Animal Research length of daylight Using Space – see www.icarusinitiative. org) should make this possible within a few years’ time. In the framework latitude of the ICARUS initiative a satellite- supported system is to be developed for permanent observation around longitude the globe of even the smallest of wildlife such as insects. Thanks to support from the German National midday Aeronautics and Space Research Centre (DLR) and numerous other cooperation partners, the initiative is The map of the world shows the division of daylight and darkness and illustrates the determination likely to prove more successful than of latitude and longitude by means of the length of daylight or the midday point. the attempts at flight by the Greek Source: http://commons.wikimedia.org/wiki/File:Daylight.png, mythological hero of the same name,

22 Der Falke 60, 2013 who plummeted into the sea with his home-made wings. The first receiver spring migration module is expected to be installed on Black Sea the International Space Station ISS from 2015. autumn migration The standard transmitter of the ICARUS system will not weigh more than 5 g and will be further minia- turised in the years following its Istanbul launch. The transmitters used in the ICARUS framework can be considerably smaller and lighter than satel- Mediterranean lite transmitters to date because the receivers on the ISS are specifically 25 km designed for and adapted to mini- transmitters, and will employ the la- Modern GPS loggers achieve high temporal and spatial definition. Shown here are the test digital communication methods. flight routes of three White Storks crossing the Bosporus on autumn and spring migra- Additionally, the ISS circumnavigates tion. The dots represent GPS coordinates at 5 minute intervals. the Earth at a height of only 400 km, whereas the satellites used by ARGOS ple recordings of ambient noise in in the near future. Bird ringing with orbit at some 850 km and therefore order to determine the song rates of its ringing centre framework has require more power for data trans- individuals, or to establish whether demonstrated how, with central and mission. an individual is alone or travel- standardised data storage, a merging In addition to high definition ling in a flock. Brain activity (EEGs, of the results of individual studies three-dimensional data the transmit- electroencephalograms) can already can result in a huge database (see pp. ters, like the GSM loggers described be recorded non-invasively on free- 34–35). Today ring recovery data are above, contain acceleration sensors. flying birds in order to determine, available not just for analysis within Every movement by the animal and for example, how homing pigeons the respective study for which they therefore, ultimately every behav- perceive the landscape or if birds in were collected, but also for analyses ioural pattern, leads to a specific spa- flight really sleep. of many more questions across larger tial movement pattern of the trans- geographic regions and long periods mitter. Once the sensors have been » Movebank of time. The Internet database www. calibrated they provide information movebank.org uses this approach to pro- on the behaviour of the individual Hundreds of studies using transmit- vide for everyone a usable platform at a set point in time. Gliding flight, ters, loggers and sensors already pro- for analysis, exchange, and perma- wing beats, swimming, or rest periods vide data on migratory movement nent storage of telemetry, geologger, can be easily identified nowadays. to a vast extent, and the amount of and similar spatially-related data. The In addition, the activity budgets of such data will increase enormously study participants can determine how wildlife can be compiled over long periods of time and can be combined 100 % with energy budgets - a further nov- Geolocators elty in behavioural research. 90 % suitable bird species (9993) by body weight » New types of sensors 80 % 70 % A large number of other sensors are GPS datalogger conceivable and in part are already 60 % available for heavier logger systems. Satellite transmitter (Doppler) Additional environmental informa- 50 % tion can, for instance, through water 40 % or air temperature measurement, salt content (e.g. for seabirds), or the GPS satellite transmitter 30 % ambient light intensity (e.g. for civi- lisation followers) be recorded and 20 % transmitted from the precise location 10 % of the bird. In the area of physiol- transmitter weight (in grams) ogy, recording of body temperature 0% and heart rate is already available 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 today in the initial systems and even Possible uses of different technology dependent on the body mass of a bird species. It is in the socio-biological context there assumed that an instrument should not weigh more than 5% of a bird’s body mass. are first developments such as sim- Illustration altered following Bridge et al., BioScience 61, 2011.

Der Falke 60, 2013 23 Bird migration

much detail of their study only they themselves, their cooperation partners, or the general public can access, and who can download their data. As is usual in the scientific community, they conduct their own evaluations under their own name, whereby in Movebank they are assisted by numerous instruments and previously prepared additional data, i.e. climate information. They are able to standardise their data in Movebank, and store them in an understandable and usable form for others – including future generations – thus increasing the value of the studies. In view of the possible additional strain that is expected of the wildlife fitted with miniature transmitters and loggers, A lightlevel geolocator on the the high costs of such studies, and the back of a Northern Wheatear shortly after fitting. Only a few urgency with which such movement Mean route of three Northern Wheatears marked in their hours after release only the spike data is required to understand wild- breeding grounds in Alaska. The birds migrated across with the light sensor jutted out of life migration and for species pro- Asia and Arabia to their East African wintering area and the plumage. tection, the use of Movebank should used almost the same route in autumn and spring. Foto: H. Schmaljohann, IfV. be taken for granted for all forms of Illustration following Bairlein et al. 2012. telemetry studies.

» Other methods Technology available for the analysis of movement patterns (altered following Robinson et al. 2010). Methods in bold type are commented on in the text. In addition to the described direct methods of tracking the migration Method Employment Limitations routes of individual birds there is Passive Integrated Identi !cation of individuals using a Range < 1 m also a series of other indirect meth- Transponder) (PIT) mobile antenna at frequently used loca- ods (see Table), of which only one (RFID – Radio Fre- tions, e.g. Breeding site, bird table; local will be described here as it can be quency Identi !cation) used harmlessly for even the smallest species. It involves the identifica- VHF Telemetry Analysis of home ranges, activity pat- For ground stations mostly up to tion of a chemical fingerprint - the (radio terns, survival rates of young birds, part- a few kilometres only; battery life tracking) ly including transmission of physiologi- in small transmitters a few days or stable isotopes - of feathers. Many cal parameters. Seldom bird migration, weeks migratory bird species moult at least following in aircraft; mostly local part of their plumage in winter quar- Satellite telemetry Migration routes and home ranges; Limited to species weighing > 150 g ters (see pp. 48 to 52). The developed worldwide Doppler locating: feather mirrors the chemical signa- Low spatial de!nition, ture of the location where it grew. GPS locating only for species weigh- In this respect, it is advantageous ing > 400 g that the Earth’s surface is chemi- Mobile communi- Home ranges, migration routes, height Limited to species weighing > 200 g cally not uniform. A freshly grown cations/ and speed, physiological parameters, dependent on system: worldwide feather carries until the next moult GSM logger environmental factors; worldwide up to a few kilometres a site-typical chemical fingerprint. If Geolocation Migration routes; worldwide Birds must be re-caught, low spatial the isotope composition of a feather de!nition: some 150 km grown in winter quarters is examined Radar Migration routes, direction, height and Low-"ying species often not re- in the breeding area, the location of speed, forecast of risk of aircraft col- corded the wintering area can be determined. lision, environmental impact studies; It has been shown, for example, that local south Swedish Willow Warblers win- Acoustic acquisi- Migration phenology; local Mostly only a few 100 m ter in West Africa, whereas those from tion north Sweden winter in East Africa. Isotope Localisation of moult areas; worldwide Low spatial de!nition This is information that could only be speculated on based solely on the few Genetic marker Allocation of individuals to populations; For many species low genetic dif- ring recoveries. (DNA) worldwide ferentiation

24 Der Falke 60, 2013 » Outlook any one time. Systematic bird ring- sarily still be required to trap birds ing remains essential, whereby the for ﬁtting with markings in order to The methods available at present, or biological study of populations, such record the large amount of necessary in the near future, permit answers to as the integrated monitoring of song- background data (population trends, be found to a large number of long birds, will be more in the foreground breeding success etc.) and provide unanswered questions that have than the analysis of migration routes. information from the surround- become ever more pressing against Radar devices also offer a means of ing environment of marked birds. a background of increasing environ- analysis of mass bird movement, as Nowadays a ‘toolbox’ is available mental pollution. On cost grounds well as in the framework of environ- for all those involved in bird migra- alone, but also for animal welfare mental impact studies, and ultimately tion research and other branches of reasons, detailed telemetry studies there are areas where the species ornithology of which previous gen- will always have to be restricted to specialist with his or her binoculars erations could only dream. It is our a relatively small number of indi- remains as before indispensable for responsibility to use it in a ﬁtting viduals. Even with the use of ICARUS collection of data on bird migra- manner. this could be just a couple of hun- tion. Indeed it is these ornithologists, Klaus-Michael Exo, Wolfgang Fiedler, dred individuals of a population at often volunteers, who will neces- Martin Wikelski

Fitting, size and weight of transmitters and loggers Dr Michael Exo is scientific researcher at the Institute of A transmitter or data logger should essentially not weigh more than 3 – 5 % Avian Research ‘Vogelwarte of a bird’s body mass. The ergonomic fitting of the transmitter is however, Helgoland’ in Wilhelmshaven. mostly more important than its precise weight. In order to reduce the effects His research and interest on behaviour, flight, diving, or manoeuvre capabilities to a minimum, the focus is Wadden Sea ecology device should be as streamlined as possible. The weights given here for dif- including fundamental nature protection research. ferent instruments are net weight, i.e. the weight without fitting material. [email protected] Whereas this is only a few additional milligrams in the case of a geolocator Dr Wolfgang Fiedler is head that is fastened with a ring, for marking with transmitters or data loggers, of the Centre for Animal using a rucksack or leg-loop harness, an additional 0.5 – 2.5 g must be calcu- Marking at the Max Planck lated. In addition to a ring or harness bonding material, fixation with fabric Institute for Ornithology in tape on the rectrices, or even an implantation, have to be taken into account. Radolfzell and current chair of the European Union of The fitting has to be species-specific optimised and should first be tested on Bird Ringing (EURING). birds in aviaries. Harnesses must often be tailored to fit individual birds. Prof Dr Martin Wikelski is the Enthusiasm for new technologies must not neglect the fact that the well- Director of the Max Planck being of the bird is of primary importance and it must be guaranteed as far Institute for Ornithology in as possible that an individual fitted with a transmitter does not behave dif- Radolfzell and Professor for ferently to an individual without a transmitter. As basically any additional the Chair for Ornithology at load - even if it is often negligible - represents an impairment, the costs (for University of Constanz. His work foci are Animal Tracking and Immu- the bird) and the use (for science) must be carefully balanced against each ne Ecology. In the time frame 2014–2020 other for every study. It must also be pointed out that in many countries the the ICARUS Initiative plans the establish- fitting of birds with transmitters or loggers always requires a permit under ment of a novel monitoring system on the the animal welfare legislation. ISS that also records very small wildlife worldwide.

Related literature: Bairlein F, Exo K-M, Schmaljohann H 2012: Eine neue Methode zur Aufklärung der Zugwege wandernder Tierarten: Geolokation. Biologie in unserer Zeit 42: 27 – 33. Fiedler W, Davidson S 2012: Mo- vebank – eine Internetplattform für Tierwanderungsdaten. Vogelwarte 50:15-20. Hobson KA, Wassenaar LI 2008: Track ing animal migration with stable isotopes. Elsevier, Amsterdam. Robinson WE, Bowlin MS, Bisson I, Shamoun-Baranes J, Thorup K, Diehl RH, Kunz TH, Mabey S, Winkler DW 2010: Integrating concepts and technologies to advance the study of Schematic depiction of the ﬁtting of a rucksack satellite transmitter on a Montagu’s bird migration. Frontiers in Ecology Harrier. Graphic: C. Trierweller. and Environment 8: 354-361.

Der Falke 60, 2013 25 Bird migration

„Out of Africa“: The evolution of bird migration Birds breed where they can ﬁnd optimal food. When these food resources are not available outside the breeding season, for instance, during the winter period, birds migrate to regions that are rich in food. Many insectivores, which exploit the arthropod-rich European summers to rear their offspring, originate in Africa, where they return as long-distance migrants after the breeding season.

irds can only occur where civores it is rather unlikely that a in the available potential dietary they can find sufficient and direct descendant would become resources. One of the preconditions Bsuitable food. Bird species a granivore. These are, of course, was not only anatomic adaptation are not free to choose their diet, trivial facts but they are significant such as flight, walking, or diving as a herbivore requires a different is answering the question as to how capabilities, but a specialisation to gastro-intestinal tract (as well as the phenomenon of bird migration the available food source. If therefore the necessary digestive enzymes) to originated. a region or habitat was rich in fish, a carni vorous species. The mode of Birds were especially successful species from the guild of piscivores nutrition is thus determined both in evolution because they were able could settle and diversify there. For genetically and phylogenetically. If to settle in almost all habitats on herbivores on the other hand, such a the ancestor of a species were pis- the planet, which differ particularly region or habitat would offer little or no possibilities for development.

» The inﬂuence of the Ice Ages on ﬂora and fauna The geographical distribution of food resources is not immutable but depends on the climate that over the past million years (in the Miocene and Pleistocene periods) has experienced regular changes of warm and cold periods (a cycle of some 100,000 years). The vegetation in the northern hemisphere today, which we accept as natural, is young in terms of the Earth’s history. Some 18,000 years ago as the last ice age in Europe reached its furthest geographic extent, a thick layer of ice covered large areas of the continent. The temperatures in the ice-free regions were similar to those in the Arctic today. In wide areas of Europe therefore, there was no deciduous woodland or grassland but rather a steppe-tundra inhabited by reindeer, mammoths, and other arctic animal

The long-distance migrant, the Golden Oriole, utilises the favourable supply of insect-rich food in Central Europe during the breeding season and then migrates south of the Sahara in order to make rich pickings there. Photo: H. Tuschl, Naturfotoarchiv Willner.

26 Der Falke 60, 2013 species. During the ice age, Africa +4 experienced widespread drought with an extensive expansion of the Sahara and a great reduction in the 0 size of the rainforests. The last ice age ended some 12,000 –4

years ago when the glaciers and ice (°C) temperature sheet melted. The released melt water –8 caused a rise in the sea level of some 120-130 m. At that stage, the North 800 000 600 000 400 000 200 000 0 Jahre Sea as we know it today was formed Pleistocene temperature cycles in the past 800,000 years. The minimum temperatures and the land bridge to Britain was correspond to glacial periods. submerged. Deciduous mixed woodland took the place of the tundra- steppe vegetation in Central Europe, which withdrew to Northern Europe. Some 10,000 years ago there was increased rainfall in the Sahara region and for several thousand years (until about some 5,000 years ago towards the end of the height of the Holocene) the Sahara was a green and fertile savannah rich in flora and fauna. Only after this period did the Sahara revert again into the desert and ecological barrier that we know today. Food availability and the distribution and migratory behaviour of bird species are closely related. ice sheet or other Polar or alpine desert permanent ice Temperate steppe grassland Last Glacial Maximum Lakes and open water Savanna Tropical extreme desert Tundra » Herbivores Vegetation Semi-arid temperate Main Taiga woodland or scrub Tropical grassland Lakes Although plant biomass is available Alpine tundra Monsoon or dry forests Steppe-tundra Tropical rainforest Continents Broadleaved temperate Montane Mosaic Subalpine parkland Tropical semi-desert in large quantities only relatively evergreen forest Temperate desert Tropical thorn scrub and few groups of birds specialise in this Dry steppe Montane tropical forest scrub woodland food resource. An animal or bird Forest steppe Open boreal woodlands Temperate semi-desert Tropical woodland would have to consume large quan- Reconstruction of the vegetation at the height of the last ice age (some 18,000 years tities of low-energy leaves or grasses ago). Source: Wikimedia Commons. to become sated and also be capable of metabolising the normally indi- gestible cell wall components and +2 poisonous secondary metabolites. Among mammals, ruminants and 0 other hoofed animals have evolved into particularly specialised her- Holocene bivores. The price of this however, optimum –2 Little was an increase in body size and, Ice Age in ruminants, the development of a voluminous ruminant stomach with –4 specially adapted microorganisms changes [°C] temperature Younger Dryas capable of breaking down cellulose. Cold Event For birds, whose bodily frame must 0 2 4 6 8 10 12 14 16 18 remain light in order to fly, the devel- thousands of years before the present opment of a ruminant stomach was clearly not a sustainable option. Temperature changes in the Holocene. The Palaeognathae, or ratites such as the Ostrich, Emu, and Rhea, which are all herbivores and today have a an early stage. Many species of Gal- widely retained their herbivorous generous body weight, mark the loanserae (i.e. swans, geese, ducks, diet; only a few species have become start of the phylogeny of modern and galliforms - that phylogeneti- piscivores or insectivores. Green birds. The ratites became flightless at cally follow the Palaeognathae) have plant material is however, also con-

Der Falke 60, 2013 27 Bird migration

Wintering Barnacle Geese in Eastern Friesland, Germany, and their migration routes and wintering area. Photo: M. Wink.

sumed by representatives of the be forgotten however that the arctic the vegetation period from late sum- bustard, crane, and rail (Coot and breeding grounds became acces- mer until early spring. This food Moorhen) families. Seeds and fruit, sible only from about 10,000 years resource is therefore generally not in which some bird families such as ago, after the end of the last ice age. available to granivores throughout grouse, doves, sparrows, many pas- During the last ice age, insofar as it the year. Granivores however, also serines, finches, and buntings have was not covered in ice, an exten- consume animal food (arthropods) specialised, are significantly richer sive steppe-tundra existed in Central that is abundantly available during in energy. Europe. The Nordic geese that today the summer half-year. Many Cen- Bird species that have specialised settle the Arctic probably bred in this tral European granivore and insec- in leaves, needles, and grasses, find Central European tundra. As the cli- tivore species (woodpeckers, tits, food almost the whole year round mate in Central Europe changed in nuthatches, sparrows, finches, and in Central Europe. It is therefore not the post-glacial period, and with it buntings) find food the whole year surprising that almost all Phasiani- the vegetation, the geese and swans round and are therefore frequently dae (grouse, partridges, and pheas- shifted their breeding grounds more resident birds. The local populations ants) are resident birds in Central and more northwards. There they are however, supplemented by new Europe. found abundant food resources arrivals from Northern and Eastern Arctic-breeding geese and swans without a great deal of competition. Europe when these areas experience find no nourishment in their breed- In order to escape the arctic winter, periods of heavy frost or heavy snow ing areas in winter; they migrate migration evolved from the Arctic cover. In these conditions seeds are southwards and winter on the coasts into climatically more favourable hard to find. Granivores are seldom of the North Sea or the large lakes in areas to the south. In Central Europe, long-distance migrants to sub-Sa- Central Asia, where sufficient food is plants do not produce seeds all the hara Africa. also available in winter. It should not year round but rather at the end of

The Arctic Tern is an exceptionally long-distance migrant, breeding in the Arctic and wintering in the Antarctic, and covering annually up to 40,000 km on its migration ﬂights. Photo: M. Wink; Map: Wikimedia Commons.

28 Der Falke 60, 2013 Matters are similar for frugivores, because the ancestors of these birds Some insectivores are quite as fruit is available from summer of prey evolved in tropical Africa. opportunistic, and species such as until early winter. Fruit is available Pisciviorous marine bird species Chiffchaff, Blackcap, Dunnock, Pied throughout the year only in the trop- (petrels and shearwaters, gannets and Wagtail, Stonechat, and Firecrest, are ics and it is there that the greatest auks) are frequently colony breeders short-distance migrants from Cen- diversity and variety of frugivores that undertake long journeys across tral Europe into the warmer Mediter- species can be found. Of our birds, the oceans after the breeding period ranean region. It can be speculated thrushes, waxwings, and some war- to find the best fishing grounds. that these species previously lived bler species are characteristic frugi- Whereas gulls are normally resident on the Iberian Peninsula, which was vores that eat fruit temporarily but or long-distance foragers, migratory not covered by steppe-tundra during are otherwise mostly insectivorous. behaviour is very pronounced in the last ice age. Only a few special- Many species in this group are part- terns and some species, such as the ist insectivores, such as the Winter migrants with some warblers, such Arctic Tern, belong to the exception- Wren, Goldcrest, and Dipper winter as the Garden Warbler, even long- ally long-distance migratory spe- here in Central Europe. These are distance migrants. cies. comparatively small species, whose dietary requirements are not as great » Carnivorous species » Insectivores as, for instance, a Hoopoe. The question as to why one species In nature the top trophic level is rep- Insectivores, or more correctly migrates as a long-distance migrant resented by the carnivorous species. arthropod-eaters, belong formally to to sub-Sahara Africa, and another Birds of prey, including falcons and the carnivorous species, but should remains resident or is a short-dis- owls, which prey on mammals and be considered separately. In Central tance migrant only to the Mediter- other birds, find food throughout and Northern Europe, insects occur in ranean area, can be discussed on the year. Many of them are resident large numbers only in late spring and several levels: birds. Only the populations in North- summer. Many insects die in autumn, s #LIMATE AND HABITAT CHANGE IN THE ern and Eastern Europe suffer from a or winter in sheltered places where Pleistocene and Holocene shortage of food in winter and these a ‘normal’ insectivore (unless it is a s 4HE PHYLOGENETIC STATUS OF A SPE- therefore migrate, in part, to climati- woodpecker, tit, or tree-creeper) can- cies in the framework of phylog- cally more favourable areas in Cen- not feed on them. The insectivores eny as a whole tral and Southern Europe as well as include a particularly large group of to Asia. Insectivorous falcons, such long-distance migratory species that Essentially the trend can be identi- as the Hobby and the Lesser Kestrel winter south of the Sahara. In this fied that bird species always become that do not find adequate food in category are the Corncrake, Coracii- migratory when they cannot find our climes in winter, are character- formes (Hoopoe, Bee-eater, Roller), food in their breeding area the whole istic migrant species and winter in cuckoos, nightjars, swifts, Wryneck, year round. This applies at least to Africa. swallows, pipits, wagtails, flycatch- the present day, some 12,000 years Exceptions to the rule are harriers, ers, many different warbler species, after the end of the last ice age. It kites, and several eagle species that small thrush species, wheatears, can be assumed that more than theoretically could also find food shrikes, Golden Oriole, and Ortolan 12,000 year ago all species that we in winter in Europe. They are how- Bunting. now know also existed then, as phy- ever, all migratory species, probably logenetic DNA analyses have dem-

The Bee-eater is a long-distance migrant that breeds in the warmer parts of Europe, North Africa, and western Asia (yellow) and winters in Africa south of the Sahara (blue). Photo: M. Wink.

Der Falke 60, 2013 29 Bird migration

mer and winter quarters, all exhibit Glossary inherited components. The genetic traits are evidently flexible, as it has Holocene - the geological epoch which began at the end of the Pleistocene been proven that some bird species (at 11,700 calendar years BP) and continues to the present. can alter their migration behaviour Miocene - the first geological epoch of the Neogene Period and extends over the course of only a few gen- from about 23 to 5.3 million years ago. erations (e.g. White Stork, Blackcap). This flexibility was probably neces- Phylogeny - the history of the evolution of a species, genus, or family etc. sary in the course of evolution as Based on their evolutionary origin species are divided into monophyletic Europe was probably settled “out taxon, within which all the members have a common ancestor. of Africa” several times in the past Pleistocene - the geological epoch which lasted from about 2.5 million periods of climate warming. Today, to 11,000 years ago, spanning the world’s recent period of repeated gla- we cannot determine whether or not ciations. the same species became migratory birds in these cycles. The European Pliocene - the period in the geologic timescale that extends from 5.3 to 2.5 birds’ life in previous warm periods million years before present. probably looked very different than it does today. As most of our species onstrated that most passerine and To begin with, the Sahara was a originated at least one million years non-passerine species frequently green savannah that did not have ago, they have successfully mastered originated as early as the Miocene to be crossed in non-stop flight, but climatic changes (otherwise they and Pliocene and at the latest in rather in stages. As the Sahara again would have become extinct). This the Pleistocene. That means that the reverted to desert some 6,000 years flexibility can help us to be optimis- species occurring today have suc- ago many species evidently devel- tic about whether and how our bird cessfully survived many cycles of oped the non-stop flight crossing. world will cope in future with the dramatic climatic changes. But even today there is still evidence climate changes forecast by clima- At the end of the last ice age that a number of species make short tologists (see pp. 58–61). the potential distribution range stopovers during their crossing of It would seem that both migra- for many of the now trans-Sahara the Sahara, as did their forebears for tion in birds and the distribution migrants (of which most species are thousands of years when the Sahara of species are subject to constant not steppe bird species) was very was still green. adaption to changing circumstances. restricted, as large regions of North If the typical long-distance If we assume that learned informa- and West Europe were covered in migrants such as Hoopoe, Bee- tion cannot be passed on, changes ice and Central and Eastern Europe eater, Roller, cuckoos, nightjars, in bird habits must be the result of was a treeless steppe-tundra. As the swifts, Wryneck, swallows, pipits, the elimination of those that fail to Sahara was also a large desert, the wagtails, flycatchers, many differ- adapt. As Heraclitus would have put only areas probably remaining for ent warbler species, small thrush it – everything flows! settlement by many species were species, wheatears, shrikes, Golden Michael Wink sub-Saharan Africa or South and Oriole, and Ortolan Bunting are con- South-east Asia. When the Sahara sidered, these are all species whose was transformed into a green savan- genus has other representatives in nah at the end of the ice age, the set- Africa (some in South-east Asia as tlement area for many insectivores well) that did not evolve into long- probably expanded to the north and distance migrants. The evolutionary Michael Wink has been tenu- progressively to Europe as well, as motto for many migratory birds that red professor for Pharmaceu- the tundra vegetation in the lat- visit us in the summer half-year (as tical Biology at Heidelberg University since 1989. His ter region was gradually replaced it is for modern man who emigrated area of research encompasses by woodland. As large amounts of from Africa some 90,000 years ago) medicinal and poisonous arthropods are available in the short- is therefore “out of Africa”. Where plants, their pharmalogical properties, as term in summer in Europe and Asia, molecular family trees are avail- well as molecular evolution, and ornitho- some species took the opportunity able (i.e. for swifts, Acrocephalus, logy. He has a particular interest in the study of phylogeny and phylogeography to settle the new regions with little Hippolais and Locustella warblers. of birds. competition. As the winters at that Wheatears, Stonechats and Whin- E-Mail: [email protected] time were also poor in nutrients for chats, and swallows) it can be insectivores, bird migration to sub- clearly perceived that the European Related literature: Saharan Africa or to tropical South- representatives of these groups are Storch V, Welsch U, Wink M 2013: east Asia began, where, during win- descended from African ancestors. Evolutionsforschung. 3. Aufl., Sprin- ter in the northern hemisphere, a The trait ‘migrant’ is clearly genet- ger Spektrum, Heidelberg. tropical climate prevails or the sum- ically determined, such that ‘zugun- Wink M 2013: Ornithologie für Einstei- mer half-year begins and sufficient ruhe’, migratory behaviour and ger. Springer Spektrum, Heidelberg. food is again available. direction, and the locations of sum-

30 Der Falke 60, 2013 Training and ProRing e. V.: Support for voluntary bird ringing

The ringing of birds in Germany is to a very large extent in the hands of voluntary ringers. The organisation, provision of rings, and their administration is the responsibility of the ringing centres, but they cannot help with the acquisition of other ringing material. This is where ProRing comes in.

he ringing of birds is an indispensable avian research method. TIt is in particular dependent on a large number of dedicated voluntary indirect employees of the ringing centres - the ringers. Bird capture and ringing demand not only a great deal of care, security, and skill in the handling of trapping equipment and the birds, but also knowledge of the legal guidelines. The road to becom- ing a ringer is therefore a long one. Normally, would-be ringers initially do an ‘apprenticeship’ under an experienced ringer. Depending on the species or task in hand, ringers must get up early in their free time, drive long distances, climb trees or hills, be good cross-country runners, A Great Reed Warbler is measured, weighed and ringed before being released. tinker around in the workshop, wade Photo: S. Klasan. through bogs by night, ward off attacks by adult birds, carry equip- » ProRing e.V. ProRing supports the evaluation ment for kilometres, get bitten by and publication of ringing project mosquitos and scratched by bram- ProRing (the German association of data. The association provides infor- bles, or ‘just’ have a very great deal friends and promoters of scientific mation by manning stalls or dis- of patience. bird ringing), with at present some tributing brochures at various pub- If they are still interested after this 370 members, supports ringers in lic events such as bird fairs. It also ‘apprenticeship’, they have to attend a their voluntary commitment. Collec- conducts deliberate public relations course at the responsible ringing cen- tive orders of ringing material are work aimed at improving the knowl- tre where the background, tasks, and offered and the association organ- edge of and understanding for this aims of bird ringing; the legal guide- ises the production of large amounts research method. ProRing is a regis- lines, implementation and organisa- of different ringing aids and passes tered charity and its work is coordi- tion; and capture and marking meth- on the discount directly to its mem- nated with the ringing centres. Fur- ods are presented and discussed. This bers. ProRing also sponsors ringing ther information on scientific bird is followed by practical training with projects, assists when problems arise, ringing and ProRing can be found at birds. Only when all this has been and conducts the Integrated Grey www.proring.de. achieved, and the desire to be a ringer Heron Monitoring and Colour Mark- Susanne Homma is still there, can an application be ing of Marsh Harriers projects. ProRing made for a certificate to conduct bird ProRing organises conferences (German association of friends and ringing, in close cooperation with and practical seminars as continua- promoters of scientific bird ringing) the responsible ringing centre and tion training for ringers, on subjects its planned activities. The ringing such as trapping methods, age, and centre then provides the now certi- sex determination; or data collection Dr Susanne Homma is a biologist working in the field fied ringer with the necessary rings and evaluation. These conferences of ornithology. She is an but not trapping equipment and other and seminars are well attended and enthusiastic ringer and Chair ringing material. To fill this latter gap also offer ringers the opportunity to of ProRing e.V. since 2004. ProRing was founded in 2002. exchange experience and knowledge. [email protected]

Der Falke 60, 2013 31 Bird migration

Colour-ringing – it‘s up to all of us

s early as 1937, the publisher especially for larger species. Swans ent projects. There are therefore cen- of the magazine ‘Vogelzug’ and large goose species in particu- tral coordinators for individual spe- A(bird migration) wrote, “The lar are also marked with coloured cies such as the Common Crane, or more random long distance recov- and coded neck collars, and wing- groups of species such as waders or eries on ringed birds fades into the tags are also used on birds of prey gulls, who monitor the use of colour background, the greater will be our and gulls. On the other hand nasal combinations and also collect the demands for identification of ringed saddles, are often used for ducks. reading reports, maintain the data- birds in the wild”. In addition to The success of colour-marking is bases, and exchange this informa- marking birds with metal rings, col- dependent on them being read. The tion with the ringing centres. oured and a variety of ‘form’ rings more participants, the faster results were introduced in order to enable are achieved and migration routes » Central structures identification of individual birds in and life stories of individual birds the field without recapture. Today, can be more precisely determined. Since 1995, the European Colour Ring this is a very widespread method This means however, that colour- Birding organisation (CR-Birding used in population and behavioural ring readings must also be prop- - www.cr-birding.org) founded by Dirk biology, but in times of excellent erly reported. In contrast to ringing Raes strives for the central record- optical equipment and digiscoping it with metal rings, which are exclu- ing of all colour-ring projects, which gains increasingly in importance in sively issued and administered by is now also supported by EU RING. bird migration research. the national ringing schemes, other CR-Birding is not however, the itting birds with individual additional forms of marking include reporting platform for colour-ring marks readable from a distance, many projects of ringers. It is there- readings, it simply collates informa- Fin addition to metal leg rings, fore more important than ever that tion on colour-ringing projects and is also widespread. Besides combi- colour-ring projects are centrally thereby avoids the duplicate use of nations of uncoded colour-rings, recorded and coordinated. Nothing colour combinations. Above all CR- colour-rings with an individual code could be more fatal than using iden- Birding provides the point of contact that can be read directly are also used tical colour combinations for differ- between the colour-ring reader, the individual colour-ring project, and the ringing centres. All colour as well as metal ring readings should be reported to the region- ally responsible ringing centre. The centre then passes on the reports to the project manager. The finder/ reader then receives the life history of the bird from either the project manager or the ringing centre. Be patient however – this procedure can take some time, particularly if there are any doubts about the identity of the bird or its marking. If feedback is not received after six months, a request for information can be made to the ringing centre by email. This procedure ensures that recoveries or readings are entered in the offi- cial national databases and are then stored for the lifetime of the respec-

Colour-ringed Spoonbills shortly after ringing on Mellum Island (Lower Saxony). Photo: B. Metzger.

32 Der Falke 60, 2013 tive project and made available for evaluation. Colour-ring readers should take care to note the colour of the ring or rings, and the code if applicable, as well as to which leg the ring is ﬁxed. The exact positioning of each ring is important when a combination of rings is used. For waders in particular, but also Spoonbills where uncoded colour rings with a small ﬂag are used in combination, the positioning is also important. The legs of the bird - right or left - are read from the bird’s perspective. When face to face with a bird the leg to your left is therefore the bird’s right leg! The same applies to wing-tags. Olaf Geiter, Franz Bairlein

Related literature: Boschert M, Fiedler W, Schmidt A 2009: Zug in den Süden – Wohin ﬂiegen Große Brachvögel vom ba- dischen Oberrhein nach der Brutzeit? Osnabrücker Naturwiss. Mitt. 35: 85-90. Cresswell W, Lind J, Quinn JL, Minder- man J, Whitﬁeld DP 2007: Ringing or colour-banding does not increase predation mortality in redshanks Tringa tetanus. J. Avian Biol. 38: 309-316. Schmidt K 2012: Langzeitstudie zur Altersstruktur einer Population der Dohle Coloeus monedula in Südwest- Thüringen mit Hilfe der Farbberin- gung. Vogelwarte 50: 169-176.

Olaf Geiter is head of the Helgoland ringing centre at the Institute of Avian Research in Wilhelmshaven. Ring recovery/reading location of Spoonbills ringed in Germany. [email protected] Daten: Overdijk/Geiter, 2002-2012

Helgoland Ringing Centre State Agency for Environment, Institute of Avian Research Nature Protection and Geology An der Vogelwarte 21 Mecklenburg-Western Pomerania D-26386 Wilhelmshaven Hiddensee Ringing Centre [email protected] An der Mühle 4 www.ifv-vogelwarte.de D-17493 Greifswald-Eldena [email protected] www.beringungszentrale-hiddensee.de Areas of responsibility of the three German ringing centres Max Planck Institute for Ornithology For historical reasons ring recov- Radolfzell Ornithological Station ery/readings from Berlin are Am Obstberg 1 handled by the Radolfzell Ornitho- D-78315 Radolfzell-Möggingen logical Station. [email protected] www.orn.mpg.de

Der Falke 60, 2013 33 Bird migration

Ringers, ringing centres, EURING and the future

In order to ﬁnd answers to numerous questions in ornithology it is indispensable to be able to identify birds as individuals. For more than 100 years the method used to achieve this has been ringing, whereas in recent times more and more additional marking and tracking techniques are employed, often of an electronic kind. Nonetheless, whether a small ring, a transponder, a logger, or a satellite transmitter is used, one aspect remains constant - nothing can be achieved without the dedication of volunteers.

ust as it is impossible to imagine affects the recovery of a ringed bird, for other, later or wider scale evalu- ornithology without the clas- clarification of the location of an ations has wider utility. Whereas this Jsic ringer, the new technologies individual with a transmitter, or the multiple use of ring recovery data via cannot dispense with the assistance collection of additional data such as ring recovery databases is common of the numerous amateur volunteers. assemblies, a network of knowledge- practice, at both national and inter- Volunteers are necessary for the col- able and cooperative ornithologists is national level, there is often a reluc- lection of metadata and background indispensable. tance to participate by those engaged information on behaviour, breeding Before an individual marking in telemetry studies. The provision biology, and population trends; as method can be applied, the bird must of presentation and evaluation plat- well as the observation of individuals first be caught temporarily or taken forms such as www.movebank.org is fitted with transmitters, or the search from a nest. In all cases this requires already a great step in the right direc- for transmitters fitted to dead birds. a permit. In contrast to ringing, the tion. Nonetheless, such databases A few professionals can conduct the fitting of transmitters or loggers also require a certain degree of supervi- observation and analysis of moving requires an animal welfare permit. In sion, not only as far as the useful- points on digital maps but contri- terms of the capture (and disturbance ness and completeness of data goes, bution of substantial new material at the breeding site) the impact of but also with regard to any questions requires a large number of volun- all methods are considered to be the related to the whereabouts of sensi- teers. same. tive species. Migratory birds, whether ringed, Ring recovery or telemetry data are Given that the use of mini-trans- fitted with transmitters, or without worthless if not published. Data that mitters and data loggers will develop either, do not stop at man-made is used for one’s own research and as comprehensively as is expected, it borders. International cooperation published is at least useful once, but is absolutely necessary to co-ordinate is therefore essential. Whether it data that is subsequently available and standardise methods and transmission frequencies. In this respect, I EURING activities an intensive discussion on the ethical judgement of telemetry methods is s Conduct analyses of ringing and ring recovery data at the European just as necessary as the establishment level of the minimum specialist require- s Coordination of a network of more than 500 standardised capture ments for persons who fit transmit- projects in the framework of capture-recapture monitoring in Europe ters and loggers to temporarily cap- s Initiation of Europe-wide ringing projects with amateur ornithologists tured birds. s Promotion of the further development of statistical and computer methods for ring recovery analysis » Europe-wide cooperation s Preparation of ringing guidelines and standards In the European ringing community, sensible procedures and understand- s Provision of a standard code for the entering and exchange of data ings have developed in all these s Establishment of the EURING database areas. The classical task of the ring- s Provision of an Internet platform for communication between ringing ing centres is structural development, centres, ringers, and the interested public. training, cultivation of contacts, and the guidance and support of volun- More information at www.euring.org teers, as well as playing a central role

34 Der Falke 60, 2013 101- 1001- 10.000- 1-10 11-100 1000 10.000 100.000 A brochure printed in several languages provides information on EURING and the many ﬁelds of application of bird ringing. It can also be downloaded as a PDF at www.euring.org/about_euring/bro- chure2007/index.html. in the licensing system. The mainte- nance of the standardised databases, the contents of which are international and still understandable after decades, are part of the daily work of these centres. As this would not be possible without international cooperation, standardisation, and agreements, the European Union for Bird Ringing (EURING) was founded in 1963. It is the amalgamation of all 39 European ringing centres and a few others outside Europe. EURING has 1-10 11-100 101-1000 1001-10.000 10.000-100.000 developed a common code for the processing of ringing and ring recov- Ringing data (upper map) and data of recoveries of dead ringed Teal (lower map) available in the EURING database. The totals per grid are depicted. eries, and set up a central database. With its numerous other activities (see Box 1) EURING is a guarantee here: http://www.euring.org/about_euring/ ity standards and replace them with for effective European cooperation in brochure2007/index.html. The Europe- something new, only because part of avian research and contributes to sci- wide ringing database comprises in the marking material no longer con- ence and nature protection in many the meantime, more than 10 mil- sists of metal rings but mini-com- diverse ways. More in the brochure lion datasets (see Box 2). It would be puters. On the contrary, these proven available as PDF in several languages ridiculous to drop such proven qual- national and international structures, established as a result of bird ring- II Data stock in the EURING database (EDB) for ringing and ring ing for which they are still required, recovery data (As at: start of 2013) (As at: start of 2013) should also be accepted and used in the ﬁeld of electronic individual Total of all datasets > 10 Million tracking methods with transmitters, Total of all species 485 loggers, or geolocators. Wolfgang Fiedler Number of species with more than 10,000 entries 87 Number of species with 1,000 to 10,000 entries 119 Dr Wolfgang Fiedler is head Number of ringing centres providing data 33 of the Centre for Animal Marking at the Max Planck Details on the EDB database and the request system for datasets from the Institute for Ornithology in EDB can be found at http://www.euring.org/edb. Quick information on the data Radolfzell and current chair of the European Union of http://www.euring.org/edb/ stock of a species can be found via the EDB index ( Bird Ringing (EURING). index.html) [email protected].

Der Falke 60, 2013 35 Bird migration

The Red List of migratory bird species

Migratory birds are subject to numerous threats in breeding areas, such as habitat loss and persecution on migration and in wintering areas. National and regional Red Lists of breeding birds have been very important indicators of species and nature conservation at risk for over 40 years. Non-breeding birds that pass through our country or use it for stopover, moult, or wintering, are less easily noted as being in need of conservation measures. This gap has now been closed for the ﬁrst time at national level by the compilation of a Red List of Migratory Bird Species. In the process, it has become clear how necessary it is to improve our knowledge about bird life outside the breeding season and to carry out more bird census schemes during migration and in winter.

he first Red List of (West) Ger- the summary of all Red Lists in Ger- to transitory or wintering species. man breeding birds was pub- many. Today, Red Lists are in the This Red List would have to be capa- Tlished in 1971 and as the first focus of public nature conservation ble of withstanding the critical tech- national Red List was thereby the policy debate, i.e. as a basis for dis- nical arguments raised by scientists forerunner for the development and cussion and decision-making. In the and nature conservation authori- adaptation of a revolutionary spe- meantime Red Lists have even found ties, as well as be receptive to new cies and nature conservation instru- their way into some legislation. For insights and amendments. ment. Other groups of organisms instance, in the National Strategy on The difficulty experienced in the soon followed, as well as lists for Biodiversity introduced by the Ger- compilation of a technically robust the federal states, which are respon- man federal government in 2007, Red List of migratory birds can be sible for nature conservation policy. concrete aims were formulated, ori- demonstrated by the somewhat triv- However, the political breakthrough entated on the levels of threat in the ial question as to what is actually occurred later in the mid-1980s, after Red Lists and which are amended in a migratory bird. As all European the publication of the 4th edition of accordance with their updates. birds are capable of flight, it is obvious that at different times of their » Not only breeding birds lifespan they travel in one direction or another. Which of these changes Red Lists of birds were formerly of location is however, relevant in restricted to the breeding season. terms of a Red List? For a long time the National Red List In the first instance, the question Committee discussed bringing year- of the units of analysis needed to round habitat usage into greater focus. This was because the breeding season is only one of several Both the status and the threat level seasonal aspects and thereby com- in the new Red List of Migratory prises only a part of species-specific Birds are marked with a super- threats. Furthermore, many bird spe- script W to enable a differentia- cies do not occur, or only occur in tion to the breeding birds list. Un- small numbers, in Germany during der regular migratory bird species the breeding season, whereas du- for instance (status IW) the Lesser ring the moult, on migration, or in White-fronted Goose is listed as winter they can play an extremely Red List (71) Category 1W (threatened with ex- Watch List (31) important role in the community of tinction), The Red-crested Pochard Least Concern (203) species. The aim was to develop a in RW (geographically restricted) structured Red List on the basis of Threat situation of migratory bird species and the Northern Lapwing in the in Germany (n = 305 species, sub-species, objective criteria, similar to that for Watch List VW. and bio-geographical populations). breeding birds that would also apply

36 Der Falke 60, 2013 be clarified. It became clear in this 50 respect that in addition to those bird species where breeding birds and new Red List arrivals could not be told apart, spe- 40 Red List with cies exist where different sub-species Watch List or indeed bio-geographical populations could, and in terms of the 30 respective endangerment, should be treated separately. From the slightly changed German bird species list of 20 2005 the Committee obtained a total of 511 species for status assessment. Share of each categoryShare (%) 10 In the new Red List of Migratory Birds however, only the 279 species that regularly migrate and with 0 appreciable migration to, through, or Short (n = 103) Mid (n = 85) Long (n = 116) out of Germany were examined more closely (within these species a further Percentage of endangered species, sub-species, and bio-geographical populations in relation to migration strategy. Left column: Percentage of the 103 short-distance migrants differentiation was made of a series listed in the Red List (red column) or in the Red List with Watch List (blue column); of sub-species and bio-geographical centre column: respective percentage of the 85 medium-distance migrants; right col- populations). In other words all bird umn: respective percentage of the 116 long-distance migrants. A former irruptive spe- species that do not migrate interna- cies, the Little Bustard, is not included in the diagram. tionally, or are migratory but occur irregularly, as well as non-indigenous bird species (neozoa) were not graphical populations in Germany, bird species are currently threatened taken into account. 66% are currently classified as of to a far greater extent than medium- Least Concern and 10 % are on the and short-distance migrants, as are » The threats Watch List. Of the 71 (23 %) species migratory species of the open coun- that were included in the actual Red tryside compared to those of the For assessment of the level of threat List, 16 are threatened with extinc- water bodies and marshlands, urban based on the established classifica- tion (“1” = CR), 26 are Endangered areas or woodland. tion scheme of the breeding bird list, (“2” = EN) and 24 Vulnerable (“3” = The new Red List of Migratory population size, long-term (50-150 VU). Five units are in the category Bird Species extends our knowl- years) and short-term (1980-2005) “Extremely Rare” (“R”) because their edge on the threat to our bird spe- population trends, and risk factors, main aggregations are geographi- cies. Migratory birds are currently were taken into account. In contrast cally very restricted (e.g. Red-crested particularly exposed to a variety of to breeding birds, the available data Pochard). additional threats outside the breed- is much sparser and differs greatly ing season. Red Lists should be more in quality. As can be expected, the It is further evident that, similar to the than a list of extinctions. Ideally best available figures are for species Red List of breeding birds, long-dis- they should lead to increased con- that are well recorded by monitoring tance migrants among the migratory servation concern with the object of programmes (Crane, waterfowl etc.). An in-house expert opinion on long- term trends was compiled on the The National Red List of Birds Committee basis of comprehensive research of the relevant literature. It was neces- The National Red List of Birds Committee is an independent organisation sary to employ a multi-stage expert instituted by the German Bird Conservation Council to prepare the German survey (Delphi method) for the iden- Red List of birds. It consists of one representative nominated by each of tification of short-term trends and the following organisations: The German Ornithologists’ Society (DO-G), the for the population size of species. German Bird Conservation Council (DRV), the Working Group of German Or- The work with this Red List made nithological Institutes, the Federation of German Avifaunists (DDA), the Na- it clear once more how essential it tional Agency for Nature Conservation (BfN) and the Association of Federal is to improve our knowledge about Bird Conservation Agencies (LAG VSW). The Federation of German Avifau- bird life outside the breeding season nists, as coordinating agency for the national bird monitoring schemes, is and to place more emphasis on com- responsible for the compilation of the database. The determination of the prehensive national bird monitoring risk factors and the assessment of threats is the responsibility of the Red programmes during migration and List Committee. The preparation of the Red List of Migratory Birds was un- in winter. dertaken by Hans-Günther Bauer (DRV), Heiko Haupt (BfN), Ommo Hüppop Of the 305 regular migratory bird (Working Group of German Ornithological Institutes), Torsten Ryslavy (LAG species, sub-species, and bio-geo- VSW), Peter Südbeck (DO-G) and Johannes Wahl (DDA).

Der Falke 60, 2013 37 Bird migration

enhancing the chances for threat- of Migratory Bird Species may con- Related literature: ened species. They should lead tribute to paving the way for better Hüppop O, Bauer H-G, Haupt H, Rys- to substantially improved human environmental and nature conserva- lavy T, Südbeck P, Wahl J 2013: Rote interaction with and management tion policies. In view of the imminent Liste wandernder Vogelarten Deutsch- of natural resources, both more sus- developments in climate change, lands, 1. Fassung, 31. Dezember 2012. tainably and more compatible with agriculture, and forestry; destruction Ber. Vogelschutz 49/50: 23-83. nature than they are at present. And of and massive use of chemicals in the Schmitz M 2011: Langfristige Bestands- trends wandernder Vogelarten the necessary measures should not countryside; as well as the continuing in Deutschland. Vogelwelt 132: stop at regional or national borders. high bird mortality due to hunting, 167–196. Politicians and society must initiate trapping, collision (glass surfaces, the long known and necessary steps rail and road trafﬁc, and technology), Dr Hans-Günther Bauer is towards an improvement of the situ- predation (cats, Mink etc.), and many a biologist and works as a ation, which are hopefully feasible more threat factors; an improvement scientiﬁc researcher at the without vast expenditure. in the situation is only possible if Max Planck Institute for greater political efforts are made than Ornithology, Vogelwarte Radolfzell. He is a member of the board of Strict protection of nature reserves has been the case to date. the European Bird Census Council (EBCC) is not adequate in itself for many Hans-Günther Bauer and coordinates the National Red List of migratory species – a much broader (for the National Red List Birds Committee. approach is required. The Red List of Birds Committee) [email protected]

The Red-crested Pochard is classiﬁed in the Category RW because of the concentration of the moult population in very few areas (“geographically restricted“). Photo: F. Derer.

38 Der Falke 60, 2013 NEW!

Atlas of Bird Migration Ring recoveries of German breeding and visiting birds

ird ringing is still one of the most important methods of bird migration research. In Germany, birds Bhave been ringed for over a hundred years. More than 20 million birds have yielded over a million recoveries, however until now, there has not been a combined account of those recoveries. The „Atlas of Bird Migration“ ﬁ lls this gap. The compiled information of the three German Bird Ringing Centres is displayed in numerous maps and concise texts. This results in comprehensive data about migration areas and winter retreats of breeding, migrating and overwintering birds. Countless voluntary contributors have improved our knowledge about birds migration. This book is an appreciation of their work. In German with English summarys for each species and English map legends, furthermore an English summary of the general introduction as well for material and methods. 1st edition 2014, about 664 pages and 600 ﬁ gures, hardcover, size 25 x 29 cm. Will be published in September 2014 Order-Number: 97-6107441 Pre-order for € 39,95

(€ 49,95 after release) 4,95 deliveryPricelevel plus € 4,95 2014, charges. Delivery starting in Germany from € 75,- post-free.

+PFWUVTKGRCTMr&9KGDGNUJGKO 6GNr(CZ Please order from: '/CKNUGTXKEG"JWOCPKVCUDQQMFGrYYYJWOCPKVCUDQQMFG Bird migration

Migratory bird conservation through international conventions For many years nature and bird conservationists have encountered difﬁculties in preserv- ing bird species, even when they spend the whole year in a particular area, or at least within a single country. Often, it is a considerably greater challenge to protect birds that, as migratory species, spend their time in different countries, or even continents, over the course of a year. It is therefore no surprise that migratory bird species show sharper population declines in comparison to resident bird species. For these species, our attention must be directed at areas much larger in geographical scale, and this is where international conventions can help.

n order to counter the decline of bird populations in Germany and Iimprove the status of endangered species, numerous important bird conservation projects, which include the support of migratory birds, have been initiated using funds from the EU (for instance from the LIFE programme), the federal states, and other public funds from foundations and associations. Nevertheless, many long-distance migrants in particular are still in an unfavourable conservation status (see pp. 54–57). The most likely population-limiting factors operating outside the breeding areas are habitat loss in the stopover and wintering areas and ongoing and widespread human persecution. The species primarily affected are those listed as ‘huntable’ in Annex II of the EU Bird Directive and which are still hunted in many EU member states despite their unfavourable conservation status throughout Europe. For instance, some 2.5 million Skylarks are still trapped each year in France, Italy, and Malta, although the population of this species in Germany has declined by some 40% over the past 20 years. The 2013 German bird of the year - the Common Snipe - can still be hunted in France, Italy, Spain, Ireland, Denmark, the United King- dom, and other EU countries despite the population declines recorded in Germany and other EU countries. The annual hunting bags for Com- mon Snipe in the EU total more than Necessary conservation measures for the Aquatic Warbler are summarised in an inter- half a million birds a year, equal to national agreement under the CMS (Bonn Convention) umbrella. Foto: Z. Morkvenas. many times the German breeding

40 Der Falke 60, 2013 population of some 5,500 to 8,500 Birds of Prey, signed by Germany foundation for more attention to be pairs. Similarly appalling figures in November 2011. There are also paid to such species as the Cuckoo, apply to Golden Plover (c. 57,000 simpler, non-binding Memoranda of Red-backed Shrike, Common Red- birds shot annually), Northern Lap- Understanding (MoUs) for individual start, Whitethroat, Sedge Warbler, wing (c. 500,000), Eurasian Curlew species such as the Siberian Crane and the Barn Swallow. The Contract- (44,000), Turtle Dove (2.3 million), and the Aquatic Warbler. Some ing Parties are currently working on and Garganey (123,000), as well as countries have decided not to be a the preparation of this action plan. many other species. German conser- signatory to the Bonn Convention On the German side, the Institute of vationists are attempting to change for political reasons. Such countries Avian Research in Wilhelmshaven this intolerable situation under the can however, be signatories to affili- plays a central role. umbrella of the German Bird Conser- ated agreements such as the AEWA Despite the necessity for greater vation Council (DRV, www.drv-web.de). or Memoranda of Understanding for consideration of conservation meas- the conservation of individual spe- ures at stopover sites and winter » Convention on Migratory Species cies. BirdLife International and its quarters outside Germany and the (Bonn Convention) national partner organisations such EU, it should not be forgotten that as the Naturschutzbund Deutschland habitat degradation or destruc- Within the EU, the Birds Directive (NABU) or the British Royal Society tion in the breeding areas is still the provides bird conservation with a for the Protection of Birds (RSPB) main reason for the decline in many definite, general, legal, and thereby play an important role in the prepa- migratory bird species. Additionally, enforceable foundation. Outside the ration and implementation of these in individual cases it can indeed be EU however, migratory birds receive agreements. possible to compensate for losses on very little protection, except in a few migration or in winter quarters by countries such as Switzerland. On » Landbirds Action Plan increasing productivity in the breed- migration and in the wintering areas, ing season. It is not therefore, a ques- illegal persecution of birds is often Until recently, a large gap existed tion of guaranteeing the conservation the result of inadequate laws and in the protection of birds through of our migratory birds in the breeding frequently the relatively poor imple- international conventions in respect area or stopover and wintering sites, mentation of national legislation. It of landbirds that breed in Europe but rather both in the breeding areas is for this reason that international and winter in Africa. However, in and in stopover and wintering sites. conventions on international nature November 2011 a landmark resolu- International conventions are an and environmental conservation are tion was agreed by the CMS Confer- important means for achieving this. so important. ence of the Parties (COP) in Bergen, Norbert Schäffer The first international agreement Norway, that should lead to signifi- was the Convention on Wetlands of cant improvements in the conser- International Importance especially vation status of African-Eurasian Dr Norbert Schäffer is a as Waterfowl Habitat, signed in the migratory landbirds. It delivered a biologist and Head of Inter- national Policy and Species Iranian city of Ramsar in 1971 and mandate for the establishment of a Recovery at The Royal So- subsequently known as the Ramsar CMS Working Group to develop a ciety for the Protection of Convention. flyway action plan for these species Birds (RSPB) in the United The most important international for adoption at the next CMS COP Kingdom. treaty for migratory birds is the Con- in November 2014. This has laid the [email protected] vention on the Conservation of Migra- tory Species of Wild Animals (CMS). Related informations: This agreement was concluded on 23 Sanderson FJ, Donald PF, Pain DJ, Burfield IJ, van Bommel FPJ 2006: Long-term po- June 1979 in Bonn and is therefore pulation declines in Afro-Palearctic migrant birds. Biol. Conservation 131: 93-105. also known as the Bonn Convention. Sudfeldt C, Bairlein F, Dröschmeister R, König C, Langgemach T, Wahl J (2012): The Convention’s secretariat has its Vögel in Deutschland 2013. DDA, Münster. offices in Bonn and is financed by CMS: www.cms.int/, www.bfn.de/0302_cms.html the United Nations Environmen- CMS regional agreements: www.bfn.de/0302_uebersicht_regionalabkommen.html tal Programme, UNEP. By signing AEWA: www.unep-aewa.org, www.bfn.de/0302_aewa.html the Bonn Convention, 114 member Ramsar: www.ramsar.org, www.bfn.de/0310_ramsar.html states have committed themselves to Agreement on the Conservation of African-Eurasian Migratory Waterbirds: the joint and targeted conservation www.cms.int/bodies/COP/cop10/resolutions_adopted/10_27_landbirds_e.pdf of particularly endangered species. www.cms.int/bodies/ScC/afr_eurasian_landbirds_wg/accra_2012_documents.htm The Bonn Convention also creates Memorandum of Understanding on the Conservation of Migratory Birds of Prey in Africa and Eurasia (Raptors MoU): www.cms.int/species/raptors/index.htm a framework for other agreements, Memorandum of Understanding Concerning Conservation Measures for the Aquatic more specialised in content, from Warbler (Aquatic Warbler MoU) the legally binding African–Eura- www.cms.int/species/aquatic_warbler/aquatic_warbler_bkrd.htm sian Migratory Waterbird Agreement www.aquaticwarbler.net/muap/index.html (AEWA) to the African-Eurasian Memorandum of Understanding Concerning Conservation Measures for the Siberian Memorandum of Understanding on Crane (Siberian Crane MoU): www.cms.int/species/siberian_crane/sib_bkrd.htm

Der Falke 60, 2013 41 Bird migration

Stopover ecology: What do migratory birds do when they rest en route? During the migration season we delight in a large number of bird species that, during their wandering, make a stopover in our local area. Although we are used to the regular coming and going of our migrant birds, we know relatively little about why they stopover in a particular area, how long they stay, or why they fly onwards in a particular direction. As migrant birds spend more actual time on stopover than in flight, and the experience at a stopover site influences the choice of the next stage of migration, research into the stopover ecology of a species is important in order to understand their migration strategy.

t was supposed to be one of those Migration conditions on the main- the Meadow and Tree Pipits and Yel- days on Helgoland that one never land would therefore dramatically low Wagtails on passage. It looked as Iforgets. The weather forecast was improve with the weakening winds though the weather and bird migra- ideal. After several days of continu- and cessation of rainfall, so that most tion forecast would be fulfilled. In the ing wide-scale weather conditions of the migrating birds could leave course of the morning the complete of a south-westerly storm combined their stopover areas on the mainland extent of this singular event became with heavy rain, the greatly slack- in the course of the night. If they took clear. During the night and the morn- ening wind was forecast to swing the route across the German Bight, ing, a mass arrival of songbirds took sharply to the south-east with an end the drizzle beginning during the night place on Helgoland. The island was to the rainfall. In addition, light driz- would force them to make a stop over blanketed, in the true sense of the zle was predicted around Helgoland on Helgoland. The early morning word, with trans-Sahara migrants. during the second half of the night. quiet would be broken by the calls of Hundreds of Common Redstarts, Whinchats and Northern Wheatears turned the open areas on the island into a jumble of red, orange, brown, and white patches of colour and twit- tering and fluttering birds in flight. Hundreds of Willow Warblers bustled about in the bushes and trees and filled them with life, while the call of an Ortolan Bunting on passage was a reminder that migration was still underway. What a day! But did the onset of drizzle actually force all the birds to land here in the second half of the night? Or were there other reasons for some birds to make a stopover here? And what do they do during their time on the island and how long do they remain? What are the factors that cause one individual to leave earlier than another? The trans-Sahara migrants among the songbirds are, with few exceptions (Swallows, Yellow Wagtails A first-year Northern Wheatear of the leucorhoa sub-species that breeds on Iceland, Greenland, or and Ortolan Buntings), characteristic Eastern Canada. A small 0.8 g radio-telemetry transmitter is fitted on its back. The signal strength of the transmitter is so strong that the exact departure time and the departure flight direction for the first night migrants. When do they leave 15 km from Helgoland can be determined. The radio-telemetry transmitter was produced by the Swiss Helgoland - and in which direction? Ornithological Institute and the Burgdorf technical college (Switzerland). The elastic loops are fitted Early or late at night? These questions around the legs. define the themes encompassed by

42 Der Falke 60, 2013 of the Palearctic-African migration system, the Wadden Sea and West Africa represent such stopover areas. These are essential in order that energy reserves for the rest of the migration route can be stored and are therefore considered to be obligatory ‘intermediate goals’ of their seasonal journey. Songbirds refuel with the amounts of energy for the required distance to be covered before crossing an ecological barrier (sea or desert). An example from the group of birds of prey is the Montagu’s Harrier, which regularly seeks out stopover sites in Northern Morocco. s Migration strategy: Nocturnal migrants land, as a rule, before sunrise. It is very probable that, with the help of visual and/or A first-year Alaskan Northern Wheatear perched on a dish filled with mealworms set acoustic information, they seek on a weighing scale. Based on the individual colour-ring combination the body weight can be recorded on every visit and its development over the complete stopover period stopover sites in the second half determined. of the night in particular, and that they end the flight stage as soon stopover ecology. They are framed by (‘emergency landing’). During the as one is found. With favourable the decision taken by a migrating bird subsequent rest phase the energy wind conditions, songbirds extend to break off a flight stage in order to reserves are restocked. their flight phase into the morning land and the later decision to resume s Stopover sites: If during a flight hours, whereas land birds migrat- migration. The questions will, inter phase migratory birds reach a good ing over the sea have to fly on until alia, be answered in the rest of this and/or traditional stopover site, the the next stopover site is reached. article, with our nocturnally migrat- flight phase is ended independent On the other hand there are the ing songbirds that winter south of the of the currently available energy daytime migrants. These are glid- Sahara in the foreground. reserves. For many wader species ing flyers dependent on thermals,

» Why do migrant birds land? The aim of the journey of migrant birds is to reach their breeding grounds or their winter quarters. The journey ends on arrival. Dependent on species, migration distance, and strategy, either a large number of stopovers or none are required. One extreme is represented by a few wader species, such as the Bar-tailed God- wit, which tops up its energy reserves close to its breeding site in order to make a non-stop flight to its winter quarters without a single stopover on the long journey. The other extreme is represented by a number of songbird species that can only master their journey of several thousand kilometres in nocturnal flights and therefore need to rest every day. There are four known reasons for a bird to end a flight stage on migration: s Energy reserves: If the energy reserves for flight are almost used up, the bird ends its flight stage A first-year Northern Wheatear at a stopover site on the Bering Straits in Alaska.

Der Falke 60, 2013 43 Bird migration

How quickly and how much energy a migratory bird is able to store during stopover is dependent on food supply and its availability. Greater intra- and interspecific competition pressure can have the consequence that some individuals can feed adequately, while others are prevented access to the common food resource. Additionally, the presence of preda- tors influences feeding behaviour. The higher the predator pressure the less nourishment is consumed. Overrid- ing these factors is the weather that has, for insectivores in particular, an influence on the fuel deposition rate of migrant birds, as low temperatures and rainfall limit the availability of insects.

» The decision to leave the stopover site Radio-telemetry work at night on Helgoland. The radio antenna, together with a compass, is fastened to a pole so that the antenna does not need to be held all night long with outstretched arm; but also so The decision to leave a stopover site that it can be held over the cliff edge to better locate the sleeping Northern Wheatears. is closely related to the reason why a bird ended its previous flight stage as well as birds of prey that use energy reserves for the onward jour- and the conditions experienced by flapping flight, and also many ney. the bird during stopover. Migratory short-distance migrants and swal- As restocking with energy during birds that did not need to replenish lows. Swifts are an exception as stopover is slower than energy con- energy reserves will continue migra- they rest in flight. sumption during flight, migratory tion at the next opportunity, whereby s Weather: Departure from a stop- birds spend more time on their long bad weather conditions will delay over site usually takes place in journeys on the ground than in the departure. The decision to depart the favourable weather conditions (no air. According to theoretical calcu- stopover site for birds that ended rain, weak winds). If the conditions lations, migrant birds spend seven the previous flight stage to rest, i.e. deteriorate as a result of approach- times more time on the ground than to refuel with energy, appears to be ing rain or storm the flight stage is in flight. This was confirmed in the influenced by the amount of energy broken off and birds land. field by Alaskan Northern Wheatears stored combined with favourable wintering in East Africa tracked by wind conditions. This is particularly » The importance of the stopover light-level geolocators. In autumn, marked in birds that do not require for migratory birds the ratio of flight time to time on the crossing an ecological barrier. The ground was 1:6. As spring migration ‘Scandinavian’ Northern Wheatears The behaviour of a migratory bird at of the Alaskan Northern Wheatear is (Oenanthe oenanthe) depart Helgo- a stopover site is influenced by the markedly faster than autumn migra- land in spring with less fuel reserves decision as to why the previous flight tion (by a factor of 1.4), the temporal and in less favourable weather con- stage was ended. If this is because of ratio (flight:ground) was only 1:3. ditions than the leucorhoa subspe- unfavourable weather conditions, or Although the energy costs per unit of cies, which has to fly the 1,400 to the end of the night or day, many of time are higher for flight than for rest, 4,000 km across the North Sea and these birds can continue their jour- the long periods on the ground have North Atlantic to reach their breed- ney when better migration conditions the consequence that the energy ratio ing grounds on Iceland, Greenland, set in, as they were not forced to between flight and rest is around 1:2. or in Eastern Canada. Individuals at end their flight phase due to energy These figures should not however, be a stopover site that are subservient shortage. If they find good feeding interpreted to show that stopovers or inferior to conspecifics and other conditions however, it is possible that are a loss-making factor for migra- competitors, or can scarcely feed they will make a longer stopover in tory birds in terms of energy. The sig- because of unfavourable food avail- order to make best use of the good nificance of stopover for migratory ability, will leave the site and seek food supply. Birds that have broken birds lies in the storing of energy better stopover conditions in close off the flight phase as a result of reserves that are consumed during proximity. These birds will often energy shortage, or the arrival at an later flight. This can only occur when backtrack on their migration route important stopover site, will then rest more energy than required is stored (reverse migration). Based on previ- as long as is necessary to refuel the during stopover. ous experience, they will most prob-

44 Der Falke 60, 2013 ably ﬁnd a more favourable stopover site than if they continued their 0,6 ﬂight in the direction of their migratory goal. More reasons explaining 0,5 the departure decisions of migratory 0,4 birds from a stopover site are discussed in an earlier FALKE article in 0,3 German (FALKE 57: 144-149). 0,2

» Decision to depart during the 0,1 night 16 17 31 Departure time relative to length of night 0 The conditions affecting the depar- Northern Wheatear Northern Wheatear Northern Wheatear ture decision by a bird on a particu- Alaska leucorhoa oenanthe Helgoland Helgoland lar day are well known. In the case of nocturnal migrants however, the Departure times relative to length of night for the Northern Wheatear during autumn question arises as to what time dur- migration in Alaska and during spring migration on Helgoland, shown separately for ing the night migration resumes. leucorhoa and oenanthe Wheatears. The departure times are shown in boxplot form. The Before departure migratory birds median is shown as a bold line, the box around the median contains 50% of the respective data, and the ‘antennae’ show the minimum and maximum values. The number calibrate their compass systems. The under the boxes denotes the sample size. The oenanthe Northern Wheatears migrate sig- necessary atmospheric calibration nificantly later at night than the other two groups. tool (polarisation pattern) can best be seen during twilight. It is therefore predicted that nocturnal migrants migrants is determined by the length In addition, energy reserves influ- depart shortly after twilight. This is of the night. An earlier start at night ence the nightly departure time. consistent with the result of radar therefore maximises the potential The more energy reserves a North- research, which describes an exodus flight duration and distance. For ern Wheatear possesses, the earlier one to two hours after sunset. Radio- Alaskan Northern Wheatears there- its departure at night. It is believed telemetry studies of Reed Warblers fore, an early start at night in autumn that high-energy reserves equate demonstrate however, that the depar- appears necessary in order to cover to a high motivation to migrate. ture time at night varies considerably, an average of 330 km per night. The A nocturnal migrant optimises its although the responsible explanatory departure time at night is probably flight stage through earlier depar- factors remain unknown. controlled endogenously and dif- ture at night. Lean birds leaving a During spring migration, North- fers between the different Northern stopover site have less motivation to ern Wheatears of both sub-species Wheatear populations according to migrate and will only fly a relatively (oenanthe and leucorhoa) departed flight distance. short distance because of the lacking from Helgoland a considerable time after the end of civil twilight - the latest departure was 5.5 hours after 360 sunset - whereby the leucorhoa

Northern Wheatears began their rapid + risky onward journey earlier than the 270 oenanthe Northern Wheatears. Inter- estingly, Northern Wheatears left a stopover site on the Bering Straits in 180 Alaska in autumn comparatively ear- Greenland lier than their relatives on Helgoland Scotland in spring. As migration to the breeding grounds is faster than that to Direction of departure [°] 90 winter quarters, it could be expected that migratory birds in spring are under greater pressure than those in 0 autumn, and therefore depart ear- 0 1000 2000 3000 4000 5000 lier at night. The Alaskan Northern Maximum !ight range (km) Wheatears must however, master a much longer migration route (c. The direction of departure across the maximum flight range of leucorhoa Northern 14,500 km) than the oenanthe (4,000 Wheatears when leaving Helgoland in spring. The direction of departure is established by radio-telemetry. The maximum flight range is estimated taking account of the - 6,000 km) and leucorhoa Northern amount of energy on departure and the prevailing wind conditions. The grey area com- Wheatears (6,000 - 8,000 km) that prises the directions in which leucorhoa Northern Wheatears flew a long (risky) stretch pass through Helgoland. The poten- across the sea, but reached their breeding grounds relatively rapidly. tial flight duration of nocturnal Diagram following Schmaljohann & Naef-Daenzer (2011).

Der Falke 60, 2013 45 Bird migration

A female northern wheatear is carrying a light-level geolocator on its back. The light sensor sticks out of the feathers just a few millimeters.

An Alaskan northern wheatear is calling. A unique combination of color-rings is used to identify individual birds.

46 Der Falke 60, 2013 energy reserves. For these birds, the North Atlantic if they did not make energy reserves and wind conditions, nightly departure time plays no sig- a stopover in Scotland. Songbirds together with a nightly departure nificant role, as with a later start at are capable of such flight perform- time, is of central significance for night they will still be able to reach ances, but would require adequately the interpretation of the departure their next goal, namely a stopover large energy reserves. Because of direction from a stopover site. From site in close proximity. The conclu- the unpredictable weather con- this we can conclude whether or sion from these considerations is ditions and the lack of stopover not a bird continues migration with that nocturnal migrants with the sites en route, this option is risky. a long flight stage, or ‘only’ leaves potential to fly long distances will A more time-consuming but safer the stopover site in order to seek a depart early at night whereas those alternative, if the energy reserves better feeding place. Only when we without such potential will leave at for a trans-oceanic flight are inad- are in possession of these facts will some time during the night. equate, would be to circumvent the we be able to properly interpret the ecological barrier. Which route do behaviour of a migratory bird at a » Direction of departure the leucorhoa Northern Wheatears stopover site. select when leaving Helgoland Heiko Schmaljohann Not only the nightly departure time, after a stopover? Birds with larger but also the direction of departure is energy reserves flew increasingly in influenced by the bird’s body condi- a north-westerly direction, whereas tion and prevailing wind conditions. ‘weaker’ birds, and those faced with Related literature: This is made clear by the example unfavourable wind conditions for Bairlein F, Förschler M, Hüppop O, of the leucorhoa Northern Wheatears crossing the North Sea left the island Schmaljohann H 2010: Vogelzug- on passage through Helgoland. in a southerly and easterly direction. forschung: Steinschmätzer als Modell. Arriving from their African winter This indicates that the birds with- Falke 57: 144-149. quarters they alter their migration out large energy reserves and wind Dierschke V, Mendel B, Schmaljohann direction at some stage from north support circumvent the ecologi- H 2005: Differential timing of spring migration in northern wheatears to north-west or even west. The most cal barrier in order to refuel some- Oenanthe oenanthe: hurried males or direct and therefore quickest route to where else. If they find a suitable weak females? Behav. Ecol. Sociobiol. the breeding grounds from Helgo- stopover site to refuel their energy 57: 470-480. land is in a north-westerly direction. reserves, they then attempt the ‘leap’ Schmaljohann H, Dierschke V 2005: That would take them some 1,700 to from there across the Atlantic. The Optimal bird migration and predation 4,000 km across the North Sea and maximum flight range derived from risk: a field experiment with northern wheatears Oenanthe oenanthe. J. Anim. Ecol. 74: 131-138. Schmaljohann H, Dierschke V 2010: Wann und in welche Richtung ziehe ich ab? Rastplatzökologische Unter- suchungen am Steinschmätzer auf Helgoland. In: Bairlein F, Becker PH (eds). 100 Jahre Institut für Vogelfor- schung „Vogelwarte Helgoland“. Aula. Wiebelsheim, 101-109. Schmaljohann H, Naef-Daenzer B 2011: Body condition and wind support initiate shift in migratory direction and timing of nocturnal departure in a free flying songbird. J. Anim. Ecol. 80: 1115-1122. Schmaljohann H, Fox JW, Bairlein F 2012: Phenotypic response to environmental cues, orientation, and costs of migration in songbirds flying half around the world. Anim. Behav. 84: 623-640.

Dr Heiko Schmaljohann’s graduate thesis at the Swiss Ornithological Institute, Sempach, and Basel Univer- sity dealt with bird migration in the Western Sahara. He now works as a German Research Foundation (DFG) Heisenberg Scholar at the Institute of Avian Research ‘Vogelwar- te Helgoland’, Wilhelmshaven, on the mi- Two Northern Wheatears and a Bluethroat at a mealworm feeder in Alaska. gration strategy of the Northern Wheatear Photos: H. Schmaljohann. [email protected]

Der Falke 60, 2013 47 Bird migration

Migratory birds in Africa Migratory birds spend only a few months of the year in their Palaearctic breeding grounds and begin the long journey to Africa in autumn, to stay there during the northern winter. Common Swifts for instance spend only three and a half months in our towns and cities but up to six months in their Central African winter quarters. Pied Flycatchers occupy territories in West Africa for half of the year. The ecology and population dynamics of migratory birds can therefore be understood only when the living conditions in Africa are known.

tudies on the wintering of Euro- sion will be limited to sub-Saharan ders from the Equator northwards pean migratory birds in Africa regions and will concentrate prima- as far as the southern fringe of the Sare still few and far between. rily on songbirds. Sahara and reaches its northernmost Research focused previously on the point in July. Subsequently, it moves location of wintering areas and the » Precipitation determines the back southwards, crosses the Equator ecological niche occupied by migra- environmental conditions and reaches its southernmost point in tory birds in the African avifauna and January. As the ITCZ is accompanied habitats; today attention is focused In tropical Africa, significant seasonal by precipitation, this falls primarily on the individual consequences of climatic differences are expressed not north of the Equator during the Euro- migratory behaviour. This article through fluctuations in tempera- pean summer and in Southern Africa will attempt to summarise the avail- ture but rather through the change during our winter months. The rainy able information on the wintering between the dry and rainy seasons. season begins later, lasts for a shorter ecology of European long-distance Their timing is caused by the north- time, and there is less precipitation migrants in Africa, identify the gaps south movement of the inter-tropical the farther it is away from the Equa- in our knowledge, and discuss which convergence zone (ITCZ) between tor. perspectives can be gained through approximately 20°N and 20°S. During These conditions have an enor- the use of new methods. The discus- the European summer the ITCZ wan- mous significance for the wintering ecology of European migratory birds. In autumn, after crossing the Sahara, they reach savannahs, which have just experienced the peak of the rainy season. The development of the vegetation and the amount of insect diet available has reached its maximum. These conditions soon alter with the rapid progression of the dry season. In contrast, dry habitats await those birds arriving during European autumn, south of the Equator. The rainy season begins in October and food availability therefore reaches its maximum in the middle of the Euro- pean winter.

» Non-stop or stopover? Many migratory bird species undertake extensive wanderings between different regions of Africa during the European winter - a behaviour

Bonelli’s Warbler, here foraging in an acacia, belongs to the species that winter in the Sahel zone immediately south of the Sahara.

48 Der Falke 60, 2013 described by Reg Moreau as ‘itiner- ancy’. In West Africa, a large number of arriving birds remain at first in the Sahel zone immediately south of the ITCZ im July Sahara. Whereas Common Redstart, Chiffchaff, Bonelli’s Warbler and Common Whitethroat spend their entire stay in Africa here; Nightin- gale, Great Reed Warbler, Garden Warbler or Willow Warbler follow Jul – Sep the precipitation southwards. Most May – Nov migratory birds remain however, north of the Equator. Mar – Dec Birds that migrate via the Nile Val- year-round ley or the Arabian Peninsula to East Africa pursue a different strategy. ITCZ im January variable As soon as they have reached the Sep – May northern savannahs they spend two or three months there to exploit the Nov – Apr abundant food supply available after Jan – Mar the rainy season and often to moult as well. In November and Decem- The location of the Inner Tropical Convergence Zone (ITCZ) determines the rainy season ber they begin again to build up in Africa (According to Jones 1995; with friendly approval of the author). fat reserves for a long journey. In a second stage of their migration they » A sedentary or nomadic life in hours. A colour-ringed Pied Fly- fly on to Southern Africa where the winter? catcher that remained in a territory rainy season is just beginning, creat- just one hectare in size for at least ing favourable conditions for winter- Some migratory bird species spend 188 days holds the record stay. The ing. As a study using geolocators has the entire time in Africa in a rela- Marsh Warbler, Whinchat, Red- demonstrated, the Thrush Nightingale tively small area. In the Northern backed Shrike, or Whitethroat also additionally makes a second stopover Ivory Coast, Pied Flycatchers arrive winter in relatively small territories. of several weeks in Kenya on its way in September and occupy territories. Migrating Northern and Isabelline from Northern to Southern Africa. These are defended against conspe- Wheatears defend their territories in After wintering, spring migration cifics in battles lasting at times for East Africa not only against conspe- takes place directly and relatively rapidly. While the autumn migration can last up to four months, spring migration lasts only some six to eight weeks. The Pied Flycatcher, which follows the longer coastal route to West Africa in autumn, flies back in spring using the direct route across the Sahara and the Mediterranean to Europe. In Eastern Africa, a generally further eastern migration route is assumed for spring than for autumn. For the Red-backed Shrike this was recently confirmed through the use of geolocators. For storks and birds of prey, satellite telemetry resulted in a different picture. White and Black Storks demonstrated no such seasonal loop migration. On the other hand, Swedish Ospreys and Marsh Harriers that winter in West Africa, cross the Sahara in spring on a more westerly route than in autumn.

The highest density of Palaearctic migratory birds is to be found in the savannahs of the Sahel zone.

Der Falke 60, 2013 49 Bird migration

up to four consecutive winters. Ter- ritorial site fidelity by some waders and birds of prey has also been confirmed by satellite telemetry. Success- ful wintering in a location probably means that the conditions will also be favourable in later years. Site fidelity thus reduces the costs of searching for suitable winter quarters. Species that do not establish a winter territory may spend the winter wandering about in flocks. The Willow Warbler mostly appears in flocks, often together with Afri- can species with a similar ecology. Aggressive behaviour is seldom seen in these flocks. The advantages of flock behaviour are obvious - many eyes see more than two. Members of a flock may be quicker to spot an approaching predator and also be able to pool their knowledge of available food.

A Spotted Flycatcher rests in an oasis in the Sahara on migration. » A wide choice with restricted use cifics but also against other Wheatear ters. In Nigeria, Yellow Wagtails were Africa, a continent three times the species. Such interspecific territorial recorded in the same territory seven size of Europe, offers a large number behaviour is however rare. years in succession. Individual Pied of different habitats. These range Once occupied, a territory is often Flycatchers and Red-backed Shrikes from deserts in the north and south sought out again in the following win- remained in the same territories for to equatorial rain forest with a series of steppe and savannah zones in between. The habitats are not, however, equally used. It is hardly surprising that migratory birds attempt to cross the Sahara in the north as rapidly as possible and avoid the southern Namib and Kalahari Deserts. This also applies, however, to the habitat that is in general the synonym for overflowing richness 139 117 204 of life - the tropical rain forest. Wulf 170 Gatter was able to demonstrate that 120 102 65 176 the habitat, and not the geographic 102 region, was avoided. After logging of The biomes of Africa und Madagascar the rain forest in West Africa, Yellow Mediterranean North Africa 43 172 Sahara Wagtails frequented the clear-felled Sahel 96 areas. The greatest density of Palae- Sudan/Guinea Savannah 122 arctic migratory birds is found in the Rain forest seasonally dry savannahs, especially Lake Victoria Basin 63 African Highlands 102 70 those directly south of the Sahara, Somali-Masai Savannah where they may indeed outnumber East African coastal forest Zambezi Bushland 20 the indigenous insectivorous song- Kalahari Highveld 70 birds. Namib-Karoo Desert Moreau was the first to point out Fynbos Scrubland West Madagascar the astounding fact that the greatest East Madagascar concentration of migratory birds is to Transitional zones be found in the habitat that, after the Palaearctic migratory birds are not distributed equally across Africa. They winter pri- deserts, seems the most unsuitable to marily on the northern and south-eastern savannahs. Map after Fishpool & Evans 2001. accommodate such a large number

50 Der Falke 60, 2013 of them: the Sahel. In West Africa in pointed out that African species and particular, an extension of the birds’ migratory birds often occur side by migration route by only a few hun- side, that aggression or interspecific dred kilometres would take them to territoriality rarely takes place, and the moister Guinea savannahs, which that some African species breed in presumably offer a greater food sup- the dry season at the same time as the ply. Additionally, immediately before habitats are used by high numbers the start of spring migration, millions of migratory birds. This all pointed of birds in the Sahel zone restock the to the fact that birds with different necessary fat reserves for crossing the migratory behaviour did not compete desert at the end of the dry season, for resources. when food is at a premium. This con- Potential competition is no longer tradiction is called Moreau’s Para- considered to be the only possible dox. It is however pointed out that reason for the spatial distribution of this paradox must be more apparent migratory and indigenous birds in than real. One explanation is that, Africa. Newer theories mention the precisely in the dry season, some of relationship between eco-morpho- the most widespread trees and shrubs logical aspects and habitat selection. in the Sahel zone are in full bloom. Long pointed wings lend the long- The consequent oversupply of nectar distance migration energy-saving attracts insects that then serve as food advantages, but are however unsuit- for the birds. The observation that able for mobility in densely-grown many birds regularly drink the nectar habitats. Another theory proposes is however relatively new. The Salt- that most migratory birds are ‘niche bush or Toothbrush Tree, Salvadora followers’, i.e. they use similar habi- persica, widespread on the southern tats in Africa to those in the breeding fringe of the Sahara, is also of great areas. As most of them breed in open Many migratory birds, such as this Olivaceous Warbler, importance. At the start of spring habitats they tend to also winter in also sing in Africa. migration from Africa it bears berries open habitats. that, for Sylvia warblers in particular, One characteristic of migratory It was assumed that insectivorous play a great role in the building up of birds is their flexibility in choice of migratory species, in comparison to fat reserves. habitat in comparison to native Afri- ecologically similar African species, Although most migratory birds can species. Willow Warblers in Zim- feed on the higher shrub and tree are found in the seasonal savannah, babwe were the only species in their areas that lie more on the fringe of among them are a few downright guild that occurred in all three habi- a given habitat. Explicit studies of specialists. One of these is the Aquatic tats that were the subject of a study, Pied Flycatcher, Willow Warbler and Warbler, which winters primarily in whereas two resident African species Red-backed Shrike could not how- the Scirpus/Sporobolus marshes of with similar ecological preferences ever confirm this. Migratory birds are the flood plains of the Senegal and were confined to one or two of the more flexible in their feeding habits. Niger rivers in West Africa. The Orto- available habitats. Pied Flycatcher and Willow Warbler lan Bunting winters in another, only partially occurring habitat in Africa, preferring highlands above 1,000 m. 100%

80% » Avifauna in Africa – competition with migrant species? 60% A few decades ago the predominant view held was that competition is the 40% driving force behind the ecology of 20% species and the dynamics of commu- nities. For a long time the question 0% was therefore posed as to how Palae- Pied Gambaga Senegal African Blue Lappen- Red-bellied Flycatcher Flycatcher Batis Flycatcher schnäpper Paradise arctic migratory birds could find suf- Flycatcher ficient resources to winter in Africa Pied Flycatchers employ a wider range of feed- !ight ground !ight as these, according to the niche the- ing techniques and are more diverse in their ory, were already used up by local application than African flycatcher species with hover !ight jumping species. Migratory birds would as a which they share the habitat. As a result, the springing !ight pecking result only occur in habitats where Pied Flycatcher is less specialised and a more a temporary surplus was unused by diverse diet is probably available to the species. African species. Critics of this theory

Der Falke 60, 2013 51 Bird migration

in the fields of orientation, physiol- ogy, and various theoretical aspects. The initial questions posed by the bird migration researcher concerning the when and where in Africa can also be answered at the species level. At the population and individual level the issue is more significant. Here the key word in the focus of interest is ‘connectivity’. Connectivity describes the degree of connection between breeding and wintering areas of individual populations. Connectivity is high when birds from a single breeding area winter in a specific region and low when breeding populations mix together in the wintering area. Knowledge of connectivity helps to explain some of the reasons for dif- fering fluctuations in population, and there are many approaches to the study of connectivity (see pp. 20 to 25). Though the catchword is new, pointers to the role of connectivity have existed for some time. After the drought in the West African Sahel zone at the end of the 1960s, popula- Sand Martins winter in large numbers in the Djoudj National Park in Senegal ... tions of some long-distance migrants in Western Europe collapsed. East- ern populations, which do not winter in the areas most affected by the drought, were much less affected. In future, one of the most important research goals will be the understanding of the relationship between … and suffer ecological conditions in the African high losses af- wintering area and individual repro- ter several con- ductive success in the breeding area. secutive days Carry-over effects describe non-fatal, of unfavourable weather with individually experienced conditions precipitation in one season that affect the survival and strong and reproductive success in another winds. season. Italian ornithologists have discovered that a presumed good food supply for Barn Swallows in their winter quarters leads to an earlier arrival in the breeding grounds. This in its turn increases the chance of second broods. Optimal conditions in the wintering area therefore increase the reproductive success in demonstrate a greater variety of feed- their cohabitation. Migratory birds the following breeding period. The ing techniques than African flycatch- are considered today to be an integral mechanisms for this can be differ- ers and Sylvia species, which implies part of the Afrotropical avifauna. ent. Food supply need not be the that a wider spectrum of diet is avail- measure of all things for a suitable able to them. It cannot however, be » Connectivity und carry-over wintering area. An analysis of sta- concluded from these observations effects ble isotopes has shown that Great that migratory birds are either more Reed Warblers that moult in differ- or less successful than resident spe- In the past few decades migratory bird ent habitats exhibit different levels cies or that competition determines research has made enormous progress of infection with bird malaria. This

52 Der Falke 60, 2013 … and the berries of the Saltbush are important basic food re- In the Sahel zone and the Southern Sahara nectar from the blos- sources for migratory birds prior to spring migration. soms of the Maerua crassifolia ... Photos: V. Salewski. could prove to be a disadvantage in The potential consequence of cli- and questions arise that can be tack- the next breeding season. An applied mate change is a further ﬁeld with led with technical innovations. We aspect of this study could lead to which bird migration research is can therefore expect further exciting the identiﬁcation and protection of occupied (see pp. 58 to 61). Over the results in future, but also that new particularly suitable wintering areas past decades great progress has been questions will emerge. because, as in Europe, the pressure made in understanding the winter- Volker Salewski on habitats used by migratory birds ing ecology of Palaearctic songbirds in Africa is steadily increasing. in Africa but ever new challenges

Moult – different strategies for an optimal flight features Volker Salewski has a doctorate in biology and cur- Breeding and migration are only two of the regularly occurring annual rently works with NABU at events. A third can be added - the moult. Growing new plumage requires the Michael-Otto-Institute high energy expenditure. The moult therefore overlaps very little with other on a Black-tailed Godwit conservation project. In energy-demanding processes such as breeding and migration. addition his interests include all aspects of Migratory birds have developed different strategies in order to attune the bird migration with a focus on wintering moult with the necessities of long-distance flight and times of favourable ecology in Africa, where he has travelled widely. [email protected] energy supply. Some, such as Pied Flycatcher and Nightingale, moult before autumn migration so that fresh wing feathers are available, but not however Related literature: for spring migration. For others the time between breeding and migration is Fishpool LDC, Evans MI 2001: Impor- too short for a complete moult. They therefore, like the Barred Warbler, inter- tant Bird Areas in Africa. BirdLife rupt the moult to resume it again in Africa or moult completely in Africa. Conservation Ser. No. 11, Pisces A moult south of the Sahara recommends itself from an energy point of Publication & BirdLife International, Newbury & Cambridge. view shortly after migration. Great Reed and Melodious Warblers that win- Jones P 1995: Migration strategies of ter in West Africa adopt this strategy, but then have to begin their spring Palearctic migrants in Africa. Israel J and autumn migration with worn plumage. In Eastern Africa some species Zoology 41: 393-406. moult during their stopover north of the Equator before they continue their Moreau R 1972: The Palaearctic- migration to Southern Africa. Only a few species such as the Barn Swallow African Bird Migration Systems. Academic Press, London. and Red-backed Shrike moult in Southern Africa. The Willow Warbler is a Salewski V, Jones P 2006: Palearctic special case. It moults completely before autumn migration and a second passerines in Afrotropical environ- time in the winter quarters, thereby always migrating with fresh plumage. ments: a review. Journal of Ornitho- Other species like the Chiffchaff, and a few Sylvia warbler species, moult logy 147: 192-201. Salewski V, Bairlein F, Leisler B 2005: only the outer flight feathers – the most worn out – in the winter quarters. Paläarktische Zugvögel in Afrika - Despite fundamentally species-specific moult strategies, individual devia- Konkurrenz mit tropischen Arten? tions always occur. Vogelwarte 44: 1-15.

Der Falke 60, 2013 53 Bird migration

Long-distance migrants live more dangerously: Population trends of German migratory birds

The monitoring programmes of the Federation of German Avifaunists (DDA) have provided information on the population development of common breeding bird species since at least 1991.

hilst it was primarily the in the time frame 1991 - 2010, almost typical bird species of twice as many species have declined Wfarmland and rural villages rather than increased in population that declined into the mid-2000s, for size over this period. For almost half several years now the majority of the species, population trends remain woodland birds have shown a nega- unchanged. Including all statisti- tive population trend as well. Only cally signiﬁcant trends (i.e. changes wetland species show almost bal- in trend of < 1% annually), the over- anced trends. all picture remains the same. Never, Taking into account only species since monitoring of common breed- that clearly increased or declined (i.e. ing birds began, has the overall bal- on average more than 1% annually) ance been so negative.

signi!cant increase unchanged/"uctuating signi!cant decline 0 10 20 30 40 50 60 No. of species

Number of bird species with a signiﬁcant trends and average annual population change of >1% between 1991 and 2010. The populations of almost twice as many species have declined than have increased. Source: DDA Monitoring of Common Breeding Birds (Line transect and point count methods).

long-distance migrant

signi!cant increase short-distance migrant unchanged/"uctuating signi!cant decline

resident, partial migrant

0 5 10 15 20 25 30 No. of species

The Sedge Warbler is a trans-Saharan migrant that win- Balance of increasing and declining breeding bird species in Germany in the time frame ters primarily in the Western Sahel. Because of higher pre- 1991 to 2010, differentiated according to migration strategies. Only those declining and cipitation in its wintering area its population has markedly increasing trends that vary by more than 1% annually are taken into account. improved over the past 20 years. Photo: R. Martin. Source: DDA Monitoring of Common Breeding Birds (Line transect and point count methods).

54 Der Falke 60, 2013 » Long-distance migrants have a problem If the migration strategies of the species are studied, it is noticeable that different ‘migration types’ are very differently affected in terms of population increase and decline. The record of short-distance migrants, i.e. those species that migrate in winter to Western Europe or to the Mediter- ranean region (Chiffchaff, Blackcap, or Meadow Pipit), is more or less in balance, with seven increasing species compared with eight in decline. The populations of 15 species have not changed fundamentally. There is also practically no change in the majority (28 from 47 species) of resident or partial migrants. Nonetheless the number of declining species (12) is almost double that of species on the increase (7), resulting in an overall negative balance. The long-distance migrants that winter south of the Sahara or in South-west Asia are however, much harder hit by population declines. Although the Grasshopper Warbler migrates in a south-westerly direction, and winters primarily in the The balance here reads 17 clearly Western Sahel, its populations have sharply declined since the mid-1990s. Photo: R. Martin. declining species as opposed to only four increasing species, a ratio of 4:1 and detailed studies on this aspect are more greatly endangered on their (some 40% of the species show no required. breeding grounds than resident birds change > 1% per year). This again However, there are indications because the migration strategy of conﬁrms what has long been indi- that long-distance migrants are also long-distance migrants is dependent cated, that long-distance migrants are markedly more threatened than other species. The reasons for this can be very different in nature and in part due to accelerating negative feedback. These are, on the one hand, dangers on the migration route such as massive bird trapping and poach- ing in the Mediterranean region; on the other, adverse changes in the wintering areas through developments such as intensive farming, including more widespread use of pesticides (e.g. agents such as DDT that has long been banned in Europe), human population growth, increasing over-grazing, destruction of rain forests, and climate change. Often too little is known about which species are affected by which factors

The Meadow Pipit is a short-distance migrant whose population has strongly and consistently declined over the past 20 years. The reasons for this lie, however, in the breeding rather than the wintering areas. Photo: T. Krüger.

Der Falke 60, 2013 55 Bird migration

on their feeding strategy. Almost all signi"cant increase long-distance migrants are exclu- south-east unchanged /#uctuating migrant signi"cant decline sively insectivorous and for this reason they leave their European breeding grounds to winter mainly in Africa. Long-distance migrants indi!erent are therefore generally more likely to be severely affected by the decline in insect populations in the breed- south-west ing areas due to use of insecticides migrant and intensive farming methods, than for instance, woodland birds which 0 2 4 6 8 10 12 partially feed on tree seeds or wood- No. of species dwelling organisms (e.g. woodpeckers, nuthatches, tree-creepers, tits). Comparative population trends of long-distance migrants in the time frame 1991 to The populations of only four long- 2010, differentiated according to main direction of migration. Source: DDA Monitoring of Common Breeding Birds (Line transect and point count methods). distance migrant species have markedly increased since 1991, the Com- mon Quail, Yellow Wagtail, Sedge Warbler, and Great Reed Warbler. At least in the case of the Common Quail and both Reed Warblers, the increases represent a recovery after previous dramatic collapses in populations in the 1960s to 1980s. The Sedge Warbler was especially nega- tively affected by the droughts in the Western Sahel (West Africa on the southern fringe of the Sahara) in the 1960s and 1970s - as has also been recorded for the Whitethroat and many other species. Due to the relatively high precipitation in the Western Sahel after 1990 the populations have since recovered to some extent. The Great Reed Warbler suf- fered from the partial drying up of its main wintering area, Lake Chad, as a result of climate change and interference with the water balance. Here Foto: M. Schäf. as well, the situation has improved somewhat since 1990. 140 %

» Birds migrating south-west 120 appear to do somewhat better These examples illustrate that the 100 developments in separate regions of Africa can indeed be very differ- 80 ent in character. The division of the trends according to the main direction of migration (mainly south-west, 60 mainly south-east, or indifferent - which means both directions in equal parts or migration on a broad front) clearly demonstrate that, because of 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 the more favourable precipitation Population development of the Red-backed Shrike in Germany in the time frame 1990 conditions over the past 20 years, the to 2010. A strong population increase in the mid-1990s was followed by a marked south-west migrants (autumn migra- population decline. The overall trend in this period is more or less unchanged. Source: DDA, combination of the trends from the Monitoring of Common Bird Species (1990-2010) and tion over south-west Europe, win- Common Breeding Bird Survey (2005-2010) (Line transect and point counts). Photo: M. Schäf. tering areas mainly in West Africa)

56 Der Falke 60, 2013 The Barred Warbler breeds primarily in Eastern Germany and The Nightingale migrates in a south-westerly direction and its winters in South-east Africa. Its population initially increased in populations have markedly increased over the past 20 years. the 1990s but since around 2000 is in sharp decline. Photo: R. Martin. Photo: S. Pfützke. are now better placed than the other tive development could be, in addi- after earlier sharp declines, to have species groups. Apart from the spe- tion to intensive bird trapping, the recovered over the past 20 years. cies with marked population recover- recent relatively widespread droughts Martin Flade, Johannes Schwarz, ies mentioned above, Reed Warbler, in East and South-east Africa, in Sven Trautmann Whitethroat, Common Redstart, and particular on the Egyptian Mediter- Nightingale all show slightly positive ranean coast (see FALKE 2013, issue Dr Martin Flade coordinated the DDA Monitoring of trends (but weaker than % annually) 6). Pesticides also appear to be used Common Breeding Birds since 1991. In the case of Whitethroat more intensively in Eastern Africa programme (old) in the time and Common Redstart, this represents than in the Sahel. frame 1989 to 2010. Since a population recovery after severe Overall, the DDA data on moni- 2013, he is Head of the population declines prior to 1990. toring of breeding birds reveal that, Schorfheide-Chorin Biosphere Reserve in Brandenburg. [email protected] Nevertheless, for the (mainly) south- since 1991, long-distance migrants west migrants there are a few mark- are affected by population declines to Johannes Schwarz, together with Martin edly declining species such as Com- a much greater degree than short-dis- Flade, steered the DDA breeding birds monitoring programmes from 1989 and until mon Snipe (due to breeding habitat tance migrants and resident bird spe- 2010, was particularly responsible for the degradation and excessive hunting cies and that the few species migrat- data input and analyses. in South-west Europe), Grasshopper ing to the south-east show particu- Sven Trautmann is employed by the DDA Warbler, and Northern Wheatear. larly negative trends. The populations for the coordination of the Common Bree- The few pronounced south-east of some species that mainly winter in ding Bird (line transect method) conducted migrants (Red-backed Shrike, River West Africa appear on the other hand, since 2004. Warbler, Sedge Warbler, Barred War- bler, Thrush Nightingale, and Red- breasted Flycatcher) show no positive Related literature: trends. The populations of these six BirdLife International 2004: Birds in Europe: Population estimates, trends and con- species have declined particularly servation status. BirdLife International, Cambridge. sharply since the end of the 1990s. Boano G, Bonardi A, Silvano F 2004: Nightingale Luscinia megarhynchos survival rates in relation to Sahel rainfall. Avocetta 28:77-85. Even in the case of the Red-backed Newton I 2004: Population limitation in migrants. Ibis 146:197-226. Shrike and Barred Warbler, the pop- Newton I 2006: Can conditions experienced during migration limit the population ulations of which in these two dec- levels of birds? J Ornithol 147:146-166. ades have changed to the extent of Sanderson FJ, Donald PF, Pain DJ, Burﬁeld IJ, van Bommel FPJ 2006: Long-term no more than 1% annually, a closer population declines in Afro-Palaearctic migrant birds. Biol Conservation 131:93- study shows that these species are 105. Wilson JM, Cresswell W 2006: How robust are Palaearctic migrants to habitat loss in sharp decline since, at the latest, and degradation in the Sahel? Ibis 148:789-800. 2000, following a population increase Winstanley D, Spencer R, Williamson K (1974) Where have all the whitethroats in the 1990s (see diagram for the gone? Bird Study 21:1-14. example of the Red-backed Shrike). Zwarts L, Bijlsma R, van der Kamp J, Wymenga E 2009: Living on the edge: Wet- The reasons for this especially nega- lands and birds in a changing Sahel. KNNV Publishing, Zeist.

Der Falke 60, 2013 57 Bird migration

Migratory birds and climate change: From long- to mid-distance migrant? Birds are extremely mobile organisms. Depending on their species-speciﬁc migratory behaviour, they travel through very different climatic and vegetation zones on their journeys. Correspondingly diverse are the challenges they are faced with on their ﬂight through changing climate and landscape in different geographical regions. Habitat changes due to climate change still have to match the temporal course of migration, breeding, and moult. This applies especially to long-distance migrants that winter south of the Sahara. They must cope with a particularly wide spectrum of habitats and climatic zones and are probably especially affected by climate change.

limate change, especially in the » Changes in spring migration shifts closer towards the pole, albeit form of changes in temperature timings with great species-specific and geo- Cand precipitation, can have an graphical differences. For Central effect on very different aspects of bird Over the past decades, temperatures and North European birds, a mean of migration. Particularly noticeable are have risen most noticeably in win- roughly one kilometre annually can changes in migration timing and ter and spring, and the ‘phenological probably be assumed. influences on condition and breeding spring’, i.e. vegetation development, Early arrival secures the best terri- success, as well as shifts in passage starts increasingly earlier. As a result tories and is particularly applicable to and wintering areas. An increase in the resources for migratory birds in birds returning in spring. A bird that migration speed in Central and West- their stopover areas and breeding cannot cope with an ever earlier start ern Europe is also likely, perhaps sup- grounds are available ever earlier in of spring is at a disadvantage in both ported by the more favourable wind the year. Together with the shift in intra- and interspecific comparison conditions that occur as a result of the vegetation periods, the distribu- because it gets only an inferior terri- climate change. tion range of wildlife and plants also tory or mate, if any at all. It probably also arrives too late for the optimum food supply for rearing of offspring. The consequence of a delayed arrival can therefore be few or no offspring at all. The vast majority of migratory birds apparently attempts to cope with the earlier onset of spring, as spring passage and arrival of the majority of bird species is also considerably earlier. Changes in phenology (the seasonal occurrence) can be confirmed very well by the trapping statistics on Helgoland. Most of the species trapped on Helgoland, in the trapping garden of the island station of the Institute for Avian Research, do not breed on the tiny island in the south-eastern North Sea. One is therefore not dependent on the evaluation of the first arrival, but can calculate the statistically more robust

One of the three tunnel traps in the Helgo- land trapping garden used for capturing small birds on stopover. Photo: K. Hüppop.

58 Der Falke 60, 2013 mean annual value of all individuals within one species trapped during a migration period. Within the past 50 years the spring migration time on Helgoland of 20 out of 23 small bird species has actually shifted forwards by up to 19 days (on average by 10 days). There was no change in the case of only three species. The long-term data from Helgoland represent a particularly impressive record of changes in spring migration phenology. In the meantime, countless datasets from many other locations have been analysed which confirm without doubt a clear trend towards earliness in spring for most species across wide areas of Europe; and also for many other parts of the planet, even when they are based only on statistically much less robust first arrival data. Migratory birds can achieve earlier The Blackcap holds the record for earliness in spring migration time on Helgoland. Photo: H. Jaschhof. arrival by departing earlier from their stopover and wintering areas, by no difference at all between the two means a longer stay in the breed- higher flight speed, or a shortening of groups. We therefore conclude that ing grounds, and thereby additional their migration routes. It is clear that long-distance migrants are able to time for more or replacement broods. for many short- and mid-distance increase their flight speed as soon as As a result, the ‘annual production’ migrants, similar wide-scale weather they arrive in Southern Europe and of young can increase, and there is systems determine the climatic con- find vegetation that is already well evidence that this is indeed the case. ditions in both wintering and breed- developed. On Helgoland we observed that sev- ing areas. The birds therefore sense eral species showed an increase in the whether the vegetation development » Consequences of earlier spring proportion of young birds on autumn in a particular year begins earlier or migration migration. On the other hand, the later, and begin migration to their number of second broods by tit spe- breeding grounds correspondingly. With constant timing of autumn cies, for instance, has decreased, and The situation is different for long-dis- migration earlier migration in spring the breeding period of trans-Saharan tance migrants. South of the Sahara they are cut off from the weather * Blackcap * Chi"cha" development in their breeding * Woodcock grounds. They have no way of know- * Lesser Whitethroat ing when spring begins in Europe. As * Willow Warbler the start of their migration is prob- * Pied Flycatcher * Blackbird ably to a great extent genetically * Spotted Flycatcher determined, it is often suspected that * Cha#nch long-distant migrants will ‘miss the * Whitethroat Redwing bus’, and could be consequently dis- * * Garden Warbler advantaged in comparison to short- * Redstart and mid-distance migrants. This * Song Thrush belief is supported by the, in part, * Robin * Wren severe collapses in the populations of * Dunnock trans-Saharan migrants. The avail- * Sedge Warbler able data on migration phenology short/mid-distance migrant * Reed Warbler long-distance migrant * Icterine Warbler is, however, contradictory. Although Ring Ouzel signi!cant the vast majority of studies indicated * Fieldfare that the very variable first records Brambling of short- and mid-distance migrants -20 -15 -10 -5 0 5 had become considerably earlier than mean change in spring migration time [days] those of long-distance migrants, the Changes in mean spring migration times over the past 50 years for 23 species difference in mean passage dates was on Helgoland based on trapping figures. A few northern European Blackcaps and much less. On Helgoland we found Chiffchaffs are long-distance migrants wintering in Africa south of the Sahara.

Der Falke 60, 2013 59 Bird migration

their prey. Despite the earlier spring Dunnock Common Redstart migration times some bird species 19.4. 9.6. arrive too late and miss out on the 9.4. 30.5. best prey supply for the rearing of their young. Nonetheless, for many 30.3. 20.5. species the dramatic habitat changes

Helgoland in the stopover and wintering areas, 20.3. 10.5. especially south of the Sahara, are R² = 0,218 R² = 0,488 y = -0,222x + 532,37 y = -0,209x + 559,26 the main reason for the decline in

mean of spring migration 10.3. 30.4. 1965 1975 1985 1995 2005 1965 1975 1985 1995 2005 their populations.

31.3. 29.4. » Changes in autumn migration timings 21.3. 19.4. In the case of autumn migration 11.3. 9.4. the picture is considerably less uniform than that of spring migration. " rst record

1.3. 30.3. Saxon Vogtland Although temperatures in summer R² = 0,143 R² = 0,233 y = -0,224x + 511,73 y = -0,229x + 557,45 and autumn have also risen, the rise 20.2. 20.3. 1965 1975 1985 1995 2005 1965 1975 1985 1995 2005 is not as great as in winter and spring. As a result, the timing of autumn year year migration has hardly changed at all, Two examples of long-term changes in spring migration times of a long-distance migrant (Common Red- and the few cases of earliness and start) and a mid-distance migrant (Dunnock) in Saxony (data from Stephan Ernst) and on Helgoland (own delay on Helgoland balance each data). The datasets have been reduced to the same time frame (1967 to 2010). other out. The reasons for this different behaviour are unclear, although migrants has not lengthened as was population declines. In terrestrial the demands of autumn migration expected. habitats plants react in their phenol- are different to those in spring. As With Pied Flycatchers, and pos- ogy more rapidly to climate change a rule, birds have more time during sibly other species, a temporal than invertebrates, and these again autumn migration. They can wait for decoupling of food supply and faster than vertebrates. Birds conse- good migration weather and stopover requirement has apparently led to quently react more sluggishly than longer on migration where food is in good supply.

» Shifts in passage and wintering areas Many short- and mid-distance migrants do not migrate these days as far as they did previously. Accord- ing to ﬁgures from North America the wintering areas of more than 250 species shifted to the north by 0.5 to 1.5 kilometres annually. Ring recoveries have revealed shifts of the same order of magnitude for Europe. In addition to Black-headed Gull, Blackbird and other species that have shortened their migration routes, other typical migratory birds such as Chiffchaff, Black- cap, Song Thrush, and Dunnock, also attempt to winter in our climes. Spe- cies that winter south of the Sahara cannot shorten their migration routes step-by-step because of the ecological barrier. Instead they must undertake a big leap in order to winter north of the Sahara; that is to change from long-distance to mid-distance migrants in one fell swoop. Indeed, Barn Swallows winter in increasing numbers in the Mediterranean region. Photo: F. Sigg. in more recent times Barn Swallows

60 Der Falke 60, 2013 The migration routes of European Black-headed Gulls considerably shortened as a result of climate change. Photo: S. Pfützke. and House Martins in particular, but particularly decisive. There, in condi- Related literature: also individual Pied Flycatchers and tions thousands of kilometres distant, Bairlein F, Exo K-M 2007: Climate change and Common Redstarts, already winter in changed climatic circumstances are migratory waterbirds in the Wadden Sea. the Mediterranean region. noticeable as a delayed reaction in Wadden Sea Ecosystem 23: 43-52. ‘our’ breeding birds. The White Stork Dierschke J, Dierschke V, Hüppop K, Hüppop is a case in point. Thanks to decades O, Jachmann KF 2011: Die Vogelwelt der » ‘Import’ and ‘export’ of the Insel Helgoland. OAG Helgoland, Helgoland. effects of climate change of ringing we are well aware of the factors that play a role with this spe- Ernst S 2013: Veränderung der Ankunftszeiten 25 häufiger Zugvogelarten im sächsischen The size of bird populations is regu- cies. Its population size in Europe is Vogtland in den Jahren 1967 bis 2011. Mitt. lated principally by the annual breed- essentially determined by effects both Ver. Sächs. Ornithologen 11: 1-14. ing success and the conditions in, and in the breeding area (temperature and Hüppop O, Hüppop K 2011: Bird migration on mortality outside, the breeding area, precipitation) and also outside it (pre- Helgoland: the yield from 100 years of re- i.e. during migration or in stopover cipitation and primary production in search. J. Ornithol. 152 (Suppl. 1): S25-S40. or wintering areas. The important the Sahel). Møller AP, Fiedler W, Berthold P 2010: Effects of Climate Change on Birds. Oxford Univer- regulatory factors are therefore not Climatic conditions in our lati- sity Press, Oxford. only the climatic conditions during tude can also have a corresponding Schmidt E, Hüppop K 2007: Erstbeobachtung the breeding season but also those effect on birds that breed farther to und Sangesbeginn von 97 Vogelarten in den in the stopover and wintering areas. the north. Mild winters which result Jahren 1963 bis 2006 in einer Gemeinde im There are indications that the amount in a decrease in the energetic qual- Landkreis Parchim (Mecklenburg-Vorpom- of precipitation in the Mediterra- ity of the mussels in the Wadden Sea, mern). Vogelwarte 45: 27-58. nean region, which influences the apparently lead to an undersupply Dr Kathrin and Dr Ommo state of the vegetation long before for the Eider ducks from the Baltic Hüppop grew up in Ham- the migrant birds arrive, decisively region and Eastern Russia that win- burg, where they both studied affects the supply of insects during ter there, and are possibly the reason biology with zoology as their stopover or wintering. for the observed decline in mussel- main subject. They lived for almost 24 years on Helgoland In the meantime it is known from eating wintering birds in the Wadden where they conducted migratory bird research several species that the precipitation Sea. Studies of Arctic geese lead us to and studied questions of seabird ecology. Ommo conditions in the Sahel have influ- expect deterioration in the food qual- Hüppop is the scientific head of the island station ence over how many birds return ity in the Central European stopover at the Institute of Avian Research ‘Vogelwarte to their European breeding grounds and wintering areas that are an indis- Helgoland’, as well as General Secretary of the German Ornithologists’ Society. Kathrin Hüppop the following year, and whether pensable precondition for success- is currently an employee of the Institute of Avian or not they breed successfully. For ful breeding and rearing in the far Research working on the German Bird Migration many species, extreme events such north. Atlas. as persistent drought in Africa are Ommo Hüppop, Kathrin Hüppop [email protected]

Der Falke 60, 2013 61 Bird migration

Offshore wind energy turbines: Possible effects of offshore wind energy turbines on bird migration

Offshore wind farms are an important building block of Germany’s new energy policy. Doz- ens of wind farms are planned, particularly in the German Exclusive Economic Zone in the North Sea. In future expansion phases, several thousand huge rotors could be in operation within a few years. To these will come converter platforms, numerous supply and service vessels, and helicopter trafﬁc. At night the structures are illuminated by marine navigation and aviation obstruction lights. Could these massive changes cause problems for migratory birds?

he licensing procedure for and horizontally rotating marine to establish by classical before-and- offshore wind farms sees the radars, microphones to record the after studies on the basis of a given T‘Threat to Bird Migration’ as a flight calls of birds on migration, number of study days. Even by day it ground for refusal. At present how- and video and thermal imaging cam- is difficult to identify a possible bar- ever, our knowledge of the effects of eras. In this way, complete migration rier effect or an increase in mortal- offshore wind turbines (WT) on bird periods are covered whereby the ran- ity as a result of collisions with the migration is still inadequate. For this domly collected data from environ- structures. reason several research projects have mental impact studies can also be Nonetheless, visual observers carry- and are being conducted concerning included. ing out standardised migration counts the possible effects of WT on bird Offshore bird migration is extremely by day from set locations can provide migration. What have they achieved variable. Due mainly to the con- important data. In this way, it was so far and what questions still remain stantly changing weather, the species established that for various duck, and open? spectrum, intensity of migration, and a few other bird species, avoidance On the research platforms FINO1 height and direction of flight fluc- behaviour plays a major role. Video and FINO3, several remote sensing tuate greatly. Causal relationships and additional radar records show methods to record bird migration are between a change in a single aspect the nature of species-specific avoid- permanently in operation the whole of bird migration and the operation ance behaviour. This at times differs year round. These include vertically of an offshore wind farm are difficult greatly between species, but can also vary from day to day within a species. Strong winds can, for instance, force Kittiwakes (which as a rule avoid WT) to go near them. The possible effects of forced diversions can be enormous in the case of large wind farms. Extended migration routes demand additional energy expenditure, which can affect not only the bird’s own survival, but also subsequent breeding success. The study of avoidance behaviour is therefore of critical importance for impact assessments and for judging the relevance of a measure. Pink-footed Geese from Spitsbergen, for example, of which

A view of the alpha ventus offshore test ﬁeld from FINO 1. The microphone for the automated recording of migratory bird calls can be seen in the foreground.

62 Der Falke 60, 2013 almost the complete population cross Non seabirds the German Bight several times a Day Night year, are very sensitive to offshore Good migration Poor migration Good migration Poor migration WTs and take wide-ranging avoid- weather weather weather weather ance measures. They are only unaf- fected by the presence of wind farms High level migration Low level migration when there is considerable free space No attraction eﬀect Attraction eﬀect to avoid them. Regional or spatial by the lighting by the lighting planning is essential. The farther out to sea the wind farms are located, the Aviodance rate very high/ Avoidance rate high/ Avoidance rate high/ Avoidance rate low/ Avoidance rate low/ passage rate very low passage rate low passage rate low passage rate high passage rate very high/ more favourable it is for migrating enticement into the birds, as many species migrate close danger area to the coast, especially by day. Very low danger Low danger Low danger High danger Very high danger of collision of collision of collision of collision of collision

» In the dark of night Increased energy Increased energy Increased energy expenditure expenditure expenditure A great part of bird migration takes place at night. With the use of radar we are able to make migration visible Increased mortality? Reduced breeding success? and record its intensity; allocation to Density-dependent … species is however only possible in regulation? exceptional cases. The recording of Effect on the population? flight calls, directly or with an auto- Diagram of possible effects of offshore wind farms on non-seabirds. The red boxes indi- matic microphone system, can be cate population-relevant influences. In addition to those shown here, many other large- of assistance. This method does not scale influences such as climate change or habitat loss have an effect on the population. work at great distances, is only of use for calling species, and it is difficult to quantify the data. Nonetheless, it This can lead to a higher number of sions need to be minimised and new is at present the only method avail- victims. Although such figures make solutions, such as the use of flashing able to record the species spectrum one sit up and take notice, they have lights instead of permanent light- at night and in poor visibility. It has a blemish - the quantitative backdrop ing, or need-based use of obstruction been established that, at night, mainly remains unclear. Even using the most lights, are very promising. An auto- songbirds such as thrushes migrate modern research methods, it is still matic recording of the calling rate across the German Bight. not possible to quantify the noctur- could help in this instance. If bird nal migratory activity at the species calls are recorded on a massive scale » Collisions level. This makes impact assessments within the danger area of illuminated difficult, as mortality caused by off- offshore structures, switching off the The species spectrum identified by shore structures cannot at present lights, and possibly the rotors of WTs flight calls is consistent with the dead be put in relation to population size. as well, could reduce the collision birds found on research platforms. Nevertheless, the numbers of colli- potential. The reason for these collisions is probably the attraction of the birds to the obstruction lights. To date, Resting Kittiwakes at FINO 1. four mass incidents have been regis- tered on FINO1, with between 88 and 199 birds, whereby the number of corpses scavenged by gulls or blown off the platform by the wind cannot be accounted for. Model calculations demonstrate however, that the actual number of birds suffering collisions is likely to be a multiple of those found, depending on wind direction and strength. Although nocturnal migration over the sea generally takes place at a lower altitude than over land, in favourable migration conditions most birds fly above the WTs. In bad visibility, however, they reduce their flight height and fly deliberately towards light sources.

Der Falke 60, 2013 63 Bird migration

Seabirds conditions than many non-seabirds. Day Night Of the latter, many migrate by day; ? frequently at a low altitude, and in Weak winds Strong winds good weather conditions are able to make a wide detour around offshore Foraging Migration Foraging Migration structures. This reduces the danger of collision to a great extent but requires higher energy expenditure. Attraction effect Avoidance rate increases/ Attraction effect Avoidance rate decreases/ for foraging passage rate decreases for foraging passage rate increases If, however, the prevailing weather by day is bad for migration, with strong winds from an unfavourable Increased danger Very low danger Considerably increased Low danger direction, flights through wind farms of collision of collision danger of collision of collision are more frequent and the danger of collision increases. Increased energy Increased energy At night on the other hand the expenditure expenditure situation is different. In good conditions most birds migrate at such high Increased mortality? altitudes that the 200 m high struc- Reduced breeding success? Density-dependent tures are unlikely to present a hazard, … regulation? and avoidance of, or flight through Effect on the population? the wind farms, rarely occurs. If the birds run into bad weather, mostly Diagram of possible effects of offshore wind farms on seabirds. The red boxes indicate population-relevant influences. In addtion to those shown here, may other large-scale in- associated with complete cloud cover, fluences such as climate change or habitat loss have an effect on the population. rain, and unfavourable winds, they fly much lower, mostly below 200 m » Where do we stand? be, for species that migrate regularly above sea level. If the birds are addi- over the sea, to differentiate between tionally attracted by the illumination The possible influences of offshore seabirds and non-seabirds in the wid- of the structures this leads inevitably wind energy facilities on bird migra- est sense. Seabirds, with their flight to a very high danger of collision. tion are complex and there are still and swimming abilities, are better In principle, WTs affect migratory many gaps in scientific knowledge. prepared to cope with the challenges seabirds in a similar way but the spe- An initial and sensible step would of the frequently extreme weather cific effects are frequently different.

Vertical rotating marine radar device on FINO 1 for recording the intensity and height of FINO 1 is occasionally used for rest by noctrunal migrants (here a Redwing). migration.

64 Der Falke 60, 2013 or the energy loss of individual birds mean for the population as a whole? Will breeding success be sustainably less as a result, or do some species balance out the losses by producing more offspring? What role do the WTs play in the light of other changes such as habitat loss or climate change? With- out this knowledge a reliable progno- sis is impossible. Ralf Aumüller, Katrin Hill, Reinhold Hill

Related literature: Aumüller R, Boos K, Freienstein S, Hill K, Hill R 2011: Beschreibung eines Vogelschlagereignisses und seiner Ur- sachen an einer Forschungsplattform in der Deutschen Bucht. Vogelwarte 49: 9-16. Aumüller R, Boos K, Freienstein S, Hill A selection of dead song birds found and collected after a night of collisions on FINO 1. Photos: R. Hill. K, Hill R 2013: Weichen Zugvögel Windenergieanlagen auf See aus? Eine Methode zur Unter- Especially in strong winds, which Seabirds are long-lived species with suchung und Analyse von Reaktionen limit their manoeuvrability, seabirds comparatively few offspring, so mor- tagsüber ziehender Vogelarten auf migrating at low altitude have great tality can have a more serious effect Offshore-Windparks. Vogelwarte 51: difﬁculty in avoiding the WTs. Dur- than on species that produce a large 3-13. ing the day, a wind farm can even number of young. Even in the case Hüppop K, Dierschke J, Dierschke V, Hill R, Jachmann KF, Hüppop O 2010: cause the birds to break off migra- of seabirds however, there is gener- Phänologie des tion to forage for food. The birds then ally too little information available to “sichtbaren“ Vogelzugs über der Deut- circle around close to the WTs and assess the consequences of WTs and schen Bucht. Vogelwarte 48: 181-267. are in great danger of colliding with identify relevant thresholds. What, for Hüppop K, Dierschke J, Hill R, Hüppop O 2012: Jahres- und tageszeitliche them as a result. example, does an increase in mortality Phänologie der Vogelrufaktivität über der Deutschen Bucht. Vogelwarte 50: 87-108. Hüppop O, Dierschke J, Exo KM, Fre- drich E, Hill R 2006: Bird migration studies and potential collision risk with offshore wind turbines. Ibis 148: 90-109.

Ralf Aumüller is an experienced ornithologist, enthusiastic birdwatcher, and scientiﬁc assistant with the Avitec Research Company. He is involved in several research projects dealing with the effects of offshore wind farms on bird migration. Katrin Hill is co-owner of the Avitec Research Com- pany and has been working for several years on various projects concerned with the effects of offshore wind farms on bird migration. Reinhold Hill is co-owner of the Avitec Research Com- pany. He has been involved for 10 years with the effects of offshore wind farms on bird migration and has coop- erated on the development of different au- Marine radar with parabolic dish antenna covered Migration counts are made from FINO 1 tomated techniques for recording offshore by a radome for recording of migration direction in the course of monitoring. bird migration. at the offshore test ﬁeld alpha ventus. [email protected]

Der Falke 60, 2013 65 Bird migration

Migratory birds and their conservation in the UNESCO – World Heritage Site Wadden Sea “Biodiversity on a worldwide scale is reliant on the Wadden Sea“, according to the ofﬁcial document of the UNESCO World Heritage Convention on its “outstanding universal value” on the occasion of the registration of the German-Dutch Wadden Sea in the World Herit- age List (under natural criteria) in 2009. This sentence describes impressively the site’s importance in a worldwide context and highlights the responsibility of the Wadden Sea states for a permanent preservation of biodiversity on the planet.

total 193 natural areas world- plays in the conservation of African- rence of Dunlin on the East Frisian wide are listed as World Eurasian migratory waterbirds. In the Islands in 1905. “This species is the ANatural Heritage sites by the Wadden Sea, up to 6.1 million birds most common of all sandpipers and UNESCO, as well as 29 further areas can be present at the same time and when autumn migration begins in that are both natural and cultural an average of 10-12 million pass August, their numbers swell to hun- sites. The Wadden Sea is on this list, through it each year.” dreds of thousands, and at high tide particularly because of the migratory they surge together into huge clouds, birds. The UNESCO states, “The Wad- » World Heritage Site – restlessly united in elegant swinging den Sea is the largest unbroken sys- also thanks to the birds over the endless mudflats.” tem of intertidal sand and mud flats Today, the permanent preservation in the world, with natural processes The ecological integrity and func- of the Wadden Sea for migratory birds undisturbed throughout most of the tionality of the Wadden Sea are forms the basis of the conservation area. It encompasses a multitude of essential for permanent preservation objectives of the National Parks. In transitional zones between land, the of the waterbird species of the Sibe- Lower Saxony, of the 52 individual, sea and freshwater environment, and rian Arctic or Eastern Canada in the strictly protected core zones, 43 alone is rich in species specially adapted to north as far as West or South Africa. were designated to include conserva- the demanding environmental condi- It was always the migratory birds that tion of the significant occurrence of tions. It is considered one of the most fascinated and attracted the coastal migratory bird species. important areas for migratory birds dwellers and above all the early con- The importance of the Wadden Sea in the world, and is connected to a servationists. Otto Leege, the most for migratory wader and waterbird network of other key sites for migra- important initiator of seabird conser- species can be explained primarily by tory birds. Its importance is not only vation in Lower Saxony and founder the abundant and productive benthic in the context of the East Atlantic of the Memmert seabird sanctuary, life in and on the mud flats, which Flyway but also in the critical role it wrote the following about the occur- enables the birds, during both phases

Brent Geese, here in the company with Common Eiders, can be observed throughout almost the entire National Park during autumn migration. Photo: R. Lottmann.Lottmann.

66 Der Falke 60, 2013 of migration, to refuel and store suf- Changes over a 23 year period (1987/1988 to 2009/2010) in percentages ficient energy for the next stage of (without Common Eider). Source: JMMB/CWSS their journey in a short period of –100 –75 –50 –25 0 25 50 75 100 125 150 time. The abundant food supply is Eurasian Spoonbill also important for breeding success in Great Cormorant the Arctic, as the bird’s condition on Barnacle Goose departure determines the chances for Northern Pintail the coming brood and the probable Sanderling level of reproductive success on the Curlew Sandpiper breeding grounds. In this respect, the sharp increase Great Ringed Plover Northern Shoveler Wadden Sea is not only a geographi- slight increase Northern Lapwing trend not signi!cant cal but also an ecological-functional Ruddy Turnstone hub on the East Atlantic flyway, with stable trend Common Gull a special ‘fuel station’ function. slight decline Grey Plover Eurasian Curlew sharp decline » Population trends are Bar-tailed Godwit fluctuating to negative Common Redshank Red Knot But what is the situation with regard Dunlin to the populations that use the Wad- Common Shelduck den Sea? A bird monitoring pro- Black-headed Gull gramme for the whole of the Wad- Pied Avocet Dark-bellied Brent Goose den Sea exists since 1992. All wader European Herring Gull and waterbird species are counted Mallard synchronously throughout the com- Great Black-backed Gull plete area on fixed dates, as well as Eurasian Oystercatcher in some counting sites every 14 days Common Teal during spring tides. This not only Common Greenshank enables a reliable record to be made Eurasian Wigeon of population size and phenology, Spotted Redshank but more importantly the calculation Whimbrel of population trends along the entire European Golden Plover Wadden Sea coastline. Currently, the Kentish Plover population developments of the 34 Ru" most important bird species (measured as their share of the simulta- to date, not be explained despite Parks (Schleswig-Holstein, Hamburg, neously occurring proportion of the comprehensive analyses. To an and Lower Saxony) have reduced bit population in the Wadden Sea) is extent, substantial regional trends by bit the negative influences on the very varied, but negative develop- can be identified. In the Netherlands, ecosystem such as human use, dis- ments predominate. The trend ana- populations of worm-eating waders turbance, and chemical pollution and lyses for the past 23 years (1987/88 tend to increase but these species are similar progress can also be claimed to 2009/2010) confirm a very sharp somewhat in decline in other areas. by the neighbouring states. The high decline throughout the Wadden Sea It is a moot point whether cockle and tide roosting sites for migratory for Ruff and Kentish Plover. In addi- mussel harvesting, which is carried birds are mostly well protected in tion, the numbers of 13 typical Wad- out primarily in the Netherlands, has the core zones of the National Parks den Sea migratory species, including led to the decline in shellfish-eating and many of them are on the islands six wader, four duck, and three gull species such as Red Knot, Eurasian well away from the main touristic species, have significantly declined, Oystercatcher, European Herring activities. Nonetheless, the negative albeit to a different degree in this Gull, or Common Eider, whereas population trends indicate emphati- time frame. Species whose popula- worm-eating species have even pos- cally that this policy must be consist- tions have increased are piscivores sibly profited as a result. Increasing ently pursued, other potential threat such as Eurasian Spoonbill and populations of the Eurasian Curlew factors must be systematically mini- Great Cormorant, as well as Bar- in Denmark are attributed to the sus- mised, and the reasons for the decline nacle Goose and two wader species pension of hunting. studied further. When considering the of the shore and sandbanks, Great population trends in the Wadden Sea, Ringed Plover and Sanderling. The » Conservation of migratory birds its integration as part of the interna- typical mud flat species therefore – only successful in a joint effort tional migration route must also be have stable or declining populations taken into account. Migratory birds - an altogether gloomy picture. The The international Wadden Sea is bet- also require favourable survival con- reasons for these critical population ter protected today than ever before. ditions at all stages of their migra- developments are unclear and can, The German federal state National tion routes. In addition, the quality

Der Falke 60, 2013 67 Bird migration

185 species in nine days: Migratory Bird Days in the Wadden Sea National Park of Lower Saxony

very year in autumn the main landscape where typical species such landmark, but because of its exposed theme in the Wadden Sea as Common Redshank and Common position, one of the best places on the ENational Park of Lower Saxony Greenshank, Ruddy Turnstone, Eura- mainland to observe migratory birds is bird migration. In 2013, the ‘Migra- sian Curlew and other wader species over the mud flats or the sea. The tory Bird Days in the Lower Saxony can be observed at close range. Flocks Kugelbake is well known as a good Wadden Sea National Park’ were held of waders can be observed on the high spot to watch birds of the high seas from 5 to 13 October for the fifth time. tide roost sites around the islands. A such as Skuas or Sabine’s Gulls from Over a nine day period, between Dol- special excursion can be made to the the mainland. On several days expe- lart and Cuxhaven, as well as on the Island of Memmert, which is normally rienced ornithologists are on hand to islands, more than 150 events cel- closed to visitors for conservation assist with observation and identifica- ebrating bird migration were organ- reasons. Memmert is one of the ‘ger- tion. ised, a programme with something minal cells’ of the National Park and In addition to the ornithological for all those interested in ornithology, has been afforded strict conservation specialist events, including lectures whether amateur or professional (www. status for decades. and presentations, there are also lots zugvogeltage.de). In 2012, a grand total Bus tours run to the Jade Bight and of other events for children or inter- of 185 bird species were observed. Dollart and offer impressive geese ested members of the public directly The most common are wader species, experiences. linked to migratory birds. These but gulls and terns, ducks and geese Experienced ornithologists lead all include art exhibitions, concerts with provide a characteristic background excursions and birdwatchers also have music from the home countries of the image, often dominating the whole the opportunity to explore the (migra- migratory birds, or menus where the tory) bird life of the Wadden Sea on different dishes are orientated on the their own. Detailed information is to countries of the East Atlantic flyway - be found in the local field guide in often accompanied by a lecture. Where German ‘Vögel beobachten im Natio- possible, the events are designed to nalpark Niedersächsisches Watten- contribute to the sustainability in the meer’ (Where to watch birds in the region, with regional, organic, or fair Wadden Sea National Park of Lower trade products. Here as well, the back- Saxony) by J. Dierschke, R. Lottmann cloth is provided by the all-encom- and P. Potel. passing motto of bird migration and A speciality is the observation sta- migratory bird conservation. tions that can only be visited during landscape. The picture is completed by the Migratory Bird Days. One of these The finale of the Migratory Bird Days many birds of prey and songbird spe- is the observation platform at Vareler is the concluding event - the ‘Zugvo- cies on passage or stopover. Hafen in the Rural District of Fries- gelfest’ (Migratory Bird Festival) - in Species such as Brent Goose, Hen land. An observation tower is erected Horumersiel. Here visitors have the Harrier, Dunlin, Bar-tailed Godwit, here especially for the Migratory Bird chance to test the latest optical equip- Common Redshank and Snow Bunting Days directly on the edge of the mud ment, obtain information on the can be seen almost everywhere in the flats from which, independent of high National Park, browse through orni- National Park during the migration or low tide, outstanding views of the thological books and magazines, or period. birds of the Wadden Sea can be expe- attend lectures and presentations. The In addition, rarities such as Great rienced throughout the day. The plat- Migratory Bird Days are an important Northern Diver, Red-footed Falcon, form is manned by trained National element of the work of the National Red-breasted Goose, Pallas’s Warbler Park employees. Another station is Park and contributes to increasing or Black-headed Bunting make guest erected on the Kugelbake, which is support for bird conservation in the appearances. not only the town of Cuxhaven’s Wadden Sea. The opportunities for birdwatchers are as varied as the number of bird species that occur. Every morning a sea-watching workshop is held on the Island of Spiekeroog, under the guidance of the experienced island ornithologist Edgar Schonart, where offshore bird migration can be studied. Ship excursions offer the chance to experience the bird life in the Wadden Sea itself. The cruise takes passengers through the mud flat

68 Der FalkeRing 60, 2013 Ouzels use the Wadden Sea for stopover on migration. Photo: R. Lottmann. The Parasitic Jaeger which breeds on the coasts of Northern Europe, also migrates along the Wadden Sea coast above all in September/October. Photo: R. Lottmann. of one station can have an effect on the condition, survival chances, and potential breeding success at other locations. In this way the individual sites – Arctic breeding area, Wadden Sea stopover, and West African wintering area – are directly dependent on and closely related to each other. These relationships between the individual areas have only very recently been comprehensively understood and they emphasise how global bird migration – very much in the spirit of the world natural heritage – and migratory bird conservation should in fact be understood. Climate change, pressure from human use, hunting, and persecution are only a few of the factors that directly and indirectly ing activities in West Africa, where Related literature: affect the living conditions of birds our Dutch colleagues are undertak- Dierschke J, Lottmann R, Potel P 2008: Vögel beobach- on migration; at different intensity, ing special efforts to extend the ten im Nationalpark Niedersächsisches Wattenmeer. and often also direction at all loca- local database. A further German- Wilhelmshaven. tions. Population development at one sponsored project in West Africa Ens BJ, Blew J, van Roomen MWJ, van Turnhout CAM location therefore always reflects serves local capacity building, i.e. 2009: Exploring Contrasting Trends of Migratory Wa- terbirds in the Wadden Sea. Wadden Sea Ecosystem No. the ecological conditions along the the strengthening of awareness and 27. Common Wadden Sea Secretariat, Joint Monitoring entire migration route. Migratory knowledge of migratory birds, and Group of Migratory Birds in the Wadden Sea, Wilhelms- bird conservation in the Wadden their conservation within the bounds haven, Germany. Sea is increasingly being developed of the East Atlantic migration route Laursen K, Blew J, Eskildsen K, Günther K, Hälterlein B, Kleefstra R, Lüerßen G, Potel P, Schrader S 2010: Migra- internationally and organised trilat- as part of a common heritage. Other tory Waterbirds in the Wadden Sea 1987 – 2008. Trend, erally (Dutch-German-Danish). The efforts are necessary in Germany to Phenology, Distribution and Climate Aspects. Wadden UNESCO has encouraged the intensi- improve the knowledge of the wider Sea Ecosystem No. 30. Common Wadden Sea Secre- fying of cooperation with the other public on migratory birds in general tariat, Joint Monitoring Group of Migratory Birds in the Wadden Sea, Wilhelmshaven, Germany. states along the migration route, in and the importance for them and glo- Leege O 1905: Die Vögel der Ostfriesischen Inseln nebst order to improve in this way the con- bal biodiversity of the Wadden Sea. einer vergleichenden Übersicht der im südlichen Nord- servation of migratory birds. In this In addition to nature conservation seegebiet vorkommenden Arten. Emden und Borkum. context, a research project sponsored and research, education and public Meltofte H, BlewJ, Frikke J, Rösner H-U, Smit CJ 1994: Numbers and distribution of waterbirds in the Wadden by the Federal Agency for Nature relations work are among the core Sea. Results and evaluation of 36 simultaneous counts Conservation has been initiated by tasks of National Parks. Over the dec- in the Dutch-German-Danish Wadden Sea 1980-1991. the Institute for Avian Research in ades, a great deal has been achieved IWRB Publ. 34, Wader Study Group Bull. 49, Special cooperation with Oldenburg Uni- in the various information centres of Issue. Smit CJ, Wolff WJ 1981 (eds.): Birds of the Wadden Sea. versity, the European White-fronted the National Park. The recognition as A. A. Balkema, Rotterdam. Goose Research Programme, and the part of the World Heritage and the Wadden Sea National Park adminis- resulting highlighted importance of Peter Südbeck is a qualified biologist with tration of Lower Saxony, dealing with the Wadden Sea for migratory birds his main focus on ornithology. He has the study of the migration routes of lends greater weight to this work. In been the Head of the Wadden Sea Nation- Arctic breeding birds (primarily Bar- addition, a new event format has been al Park administration of Lower Saxony since 2005. Previous to this appointment tailed Godwit and Grey Plover) using developed in Lower Saxony to com- he was Head of the Lower Saxony State geolocators and satellite transmit- municate this issue from various per- Ornithological Station for many years. ters. The study of carry-over effects spectives to a large number of groups [email protected] between stopover and wintering areas and interested persons and sectors of Gundolf Reichert is a qualified landscape and the Arctic breeding grounds of society, so that more and more peo- conservationist, and as ornithologist in Geese on Kolguyev Island is also the ple are aware and thereby strengthen the National Park administration has subject of a research project. Trilat- and actively support migratory bird been responsible for all specialist matters erally, a Wadden Sea Flyway Ini- conservation in the Wadden Sea. concerning bird species protection, bird research, and monitoring since 2010. He www.waddensea- tiative was initiated ( Why not join them and come to the worked previously in a planning office. secretariat.org/management/ projects/ coast, for example, during the annual flyway-initiative) that is intended to Migratory Bird Days in the Wadden Petra Potel is a qualified biologist and has worked in the Sea National Park admin- strengthen permanently the coopera- Sea National Park of Lower Saxony istration in the field of bird conservation tion between the individual partners held every autumn? since 1992. She has been responsible for along the migration route. The focus Peter Südbeck, Gundolf Reichert, the concept and organisation of Migratory of the initial projects is monitor- Petra Potel Bird Days in the National Park since 2009.

Der Falke 60, 2013 69 Bird migration

How can ornitho.de contribute to bird migration research? The start of ornitho.de, an online portal for entering ornithological observations, on 30 Octo- ber 2011 changed the collecting of avifaunistic data in Germany considerably. By June 2013 over 5 million sightings from more than 6,000 persons had been entered in the portal. In the past, many of these records had gone no further than the individual’s ﬁeld notebook, or were perhaps not noted at all, let alone made available in a central database. It undoubtedly represents a massive wealth of data for migratory bird research, which is growing and increasing in value from day to day. The so-called ad hoc or casual observations that are collated in ornitho.de are not, however, without their pitfalls. On the occasion of the publication of this special edition of Der Falke we intend to follow up the question posed in the title of this article, and examine a little more closely its possibilities and limitations.

f questions are to be answered on a scientific basis, the collection Iof data is usually strictly standardised and systematic. Sampling effort and recording methods are known and assumptions can thus be made. Data are also comparable and statistically sound analyses can be carried out. In scientific bird ringing, for instance, clear guidelines are laid down for recording wing and beak length, weight or moult score; and in the common breeding bird census the counts are made on statistically representative 1x1 km plots, in pre- defined time periods, and according to standardised methods. This makes data analysis considerably easier. There are however, no guidelines for casual observations – that is all observations that are collected in an unsystematic way. If I make an observation that I, for whatever reason, personally find interesting, I submit it to ornitho. de. For one observer these are, for instance, all sightings of Red- backed Shrikes during the breeding season. For another, only the first sighting of the species is interesting, and yet another records every Lesser Spotted Woodpecker, or only Grey-headed Wagtails M. thunbergi breed in Scandinavia and Russia and occur in Central Red-breasted Goose or similarly Europe on passage only. Based on the data from ornitho.de a marked concentration ap- rare species. I can therefore decide pears to occur in the Western half of Germany, which supports the sparse information myself, at any time, what and if I available on a migration route across Western Europe. Random observations can be an report. This, amongst other things, important augmentation for research into migration routes of bird species where information from scientific bird ringing is still incomplete. The map shows the total of all in- makes online portals for casual dividuals reported at a location. Some dots appear larger because of multiple sightings. observations attractive.

70 Der Falke 60, 2013 It is clear that this freedom to report 60 8 observations restricts the possibilities for data analysis. Observations accu- 7 mulate in well-populated areas and 50 also in the attractive birdwatching 6 sites in these areas. For most of us 40 our free time is generally at the week- 5 end, so a disproportionate number of observations are made on Saturdays 30 4 and Sundays, and these are in almost all cases positive records of indi- 3 vidual species. It therefore remains 20 unknown which other species were 2 No. of complete lists with records [%] present or which species were absent. Distribution of individual sightings [%] In general and straightforward terms, 10 1 it can be said that the more rare or attractive a species or event is (e.g. 0 0 the arrival of migrants, Common Ja n Feb Mar Ap r May Ju n Jul Au g Se p Oct No v Dec Crane passage), the more complete Date [Week] and therefore more reliable are the Seasonal occurrence of the Barn Swallow in 2012 according to data from ornitho.de casual observations. Or in reverse, the a) based on individual sightings (columns) as well as b) complete lists (lines; blue - 2012, more frequent and common a species red – 2013). All species discovered on an excursion are recorded in complete lists. On the is, the more important is a systematic basis of the latter, the seasonal occurrence is depicted much more realistically than when approach to the recording of casual based on individual sightings, according to which the pattern resembles that of a migrant observations. breeding at northern latitudes. The reason for this is the dwindling interest of the observer after the arrival of the ﬁrst individuals in spring. The somewhat later arrival of the In ornitho.de and other online por- Barn Swallow in 2013 cannot be detected because records are summarised by weeks. The tals this ‘semi-systematic’ approach percentage of individual sightings and the number of complete lists with Barn Swallow is implemented using complete lists. records per week is depicted respectively.

In many places in Germany the males predominate in flocks of wintering Common Pochards. The females move away farther south. Data from ornitho.de data combined with the results of the Waterbird Census should provide sufficient data in order to analyse sex- specific wintering strategies. Photo: C. Moning.

Der Falke 60, 2013 71 Bird migration

conditions in the main breeding areas are often the trigger for Schleswig-Holstein/Hamburg influxes. These can also be well Mecklenburg-West Pomerania documented by casual observa- Lower Saxony/Bremen tions, as they attract the interest of Brandenburg/Berlin a wider public. Based on this data, Saxony-Anhalt origin and migration movements North-Rhine Westphalia can also be partially analysed. Saxony Examples of this are the arrival of Thuringia Rough-legged Buzzards in winter 2011/12, the unusually large occur- Hesse rence of the Black-winged Stilt in Rhineland-Palatinate May 2012, or the Waxwing inva- Saarland sion in winter 2012/13. Bavaria Baden-Württemberg Ornitho.de is not an island unto itself. In almost all countries in Northern or 1 11 21 1 11 21 31 Western Europe there is an online April May portal for collection of casual data In 2013 (red) the Red-backed Shrike obviously arrived in many locations earlier than in and millions of data are collected 2012 (blue), especially in Southern Germany. Red-backed Shrikes winter in East Africa annually. If the consolidation on an and therefore arrive in Germany from a south-easterly direction. In the future data international level of the data from from ornitho.de can contribute to the analysis of the annual variability of the wide- all these portals can be achieved, a scale arrival of bird species or the differences between individual migration routes. The completely new perspective on the tenth record is represented by a dot and the first and twentieth record by a line denot- ing the spread of arrival. Only one record per day and location was used. Source: ornitho.de. migratory movements of birds will be opened – not only for all birdwatchers but also for researchers of migra- In this approach all species seen or for the year, and an increasing tory birds. heard on an excursion are noted so number pass on their observations Johannes Wahl, Christopher König, that during data analysis the conclu- as complete lists. The arrival of Stefan Stübing sion is permissible that all species not many species, as well as the dif- noted on the list were not sighted (the ferences between regions and the strongly varying detectability between annual variability, can therefore be individual species or between seasons precisely described. It was shown in Related literature. is a problem that also affects moni- 2013 that short-distance migrants Newton I 2010: Bird Migration. Collins toring programmes – but this can be arrived considerably later, but that New Naturalists Series 113. König C, Stübing S, Wahl J 2013: Früh- dealt with statistically). the late arriving long-distance jahr 2013 – Späte Kurzstreckenzieher, These zero values are essential if migrants arrived with us somewhat frühe Langstreckenzieher. Falke 60: answers are to be provided to many earlier than in the year before. A 274–279. questions and – what is often forgot- long-term comparison provides These, and all other publications con- ten – these are full-value information. interesting perspectives in terms taining analyses of data from ornitho. Complete lists also provide informa- of possible trends in the seasonal de are available (in German) and can tion on the time spent and area cov- occurrence of migratory bird spe- be downloaded from www.dda-web.de/ ered during an excursion. All these cies. publikationen. factors increase the potential for data s &OR MANY SPECIES THE DIFFERENCES analysis to a considerable extent. between the sexes or between adult Dr Johannes Wahl (top) and Christopher König both and young birds can be well dis- work for the DDA. Among » Wide-scale analysis of bird tinguished, so that they can often other topics, they are re- migration phenomena is possible be reported separately. In this way sponsible for ornitho.de and questions on migration strategies dedicate a lot of their time If one is aware of this background, the and temporal and spatial differences to supporting and running the portal. random observations from ornitho.de in occurrence can be answered on can represent an important augmen- a broad basis and possible long- Stefan Stübing works as a tation for a whole series of questions terms trends can be analysed. The biologist. He is the DDA‘s on the systematic, yet ne cessarily first examples of such evaluations deputy chairman and acts mainly selective approaches in migra- on the Ring Ouzel, Whooper Swan, as avifaunistic coordinator of the HGON, the DDA‘s tory bird research: and Dotterel have already been partner organsiation of the s 4HE ARRIVAL OF MIGRATORY BIRDS IN published in earlier issues of DER federal state of Hesse. spring captivates us afresh year FALKE. For more details on ornitho. after year. Most observers therefore s !BOVE AVERAGE BREEDING SUCCESS de please contact Johannes Wahl directly: report their personal first records food shortages, or unfavourable [email protected].

72 Der Falke 60, 2013 End