Ulrich Querner

Heritability of the timing of autumn migration in a natural bird population

In recent decades, global temperature has increased at an unprecedented rate. This has been causing rapid environmental shifts that have altered the selective regimes determining the annual organization of birds. In order to assess the potential for adaptive evolution in the timing of autumn migration, we estimated heritabilities of the onset of migratory activity in a southern German blackcap (Sylvia atricapilla) population. Heritabilities (h2 = 0.34-0.45) and coefficients of additive genetic variation (CV2 = 4.7-5.7) were significant and consistent when estimated by different methods, irrespective of whether they were derived from birds hatched in the wild or bred in captivity. In an artificial selection experiment, we selected for later onset of migratory activity, simulating expected natural selection on this trait. We obtained a significant delay in the mean onset of migratory activity by more than one week after two generations of selection. Realized heritability (h2 = 0.55) was in agreement with expected heritability in the cohort that the selection line was derived from. Our results suggest that evolutionary changes in the timing of autumn migration may take place over a very short time period and will most probably be unconstrained by the lack of additive genetic variation.

Migratory orientation of first-year white storks (Ciconia ciconia): inherited information and social interactions.

SUMMARY We used satellite tracking to study the migratory orientation of juvenile white storks from the population in the Kaliningrad Region (Russia) during their first autumn migration. Two series of experiments were performed. In the first series of experiments, several groups of first-year storks were raised in an aviary, kept there until all free-living conspecifics had left the area and then released. These birds had to select their migratory route on the basis of the inherited directional information they possessed, without any chance of being guided by their experienced conspecifics. In the second series of experiments, several groups of juveniles were displaced from the Kaliningrad Region to the Volga area and to Western Siberia. Both areas lie outside the breeding range of the white stork so the displaced birds also had to rely on their innate migratory program. Results from the differently designed experiments did not match. Nor did they match with the results of earlier experiments on the delayed departure of juvenile white storks as reported by several authors. We suggest that naïve white storks (and maybe other soaring migrants) rely on social interactions when selecting their autumn migratory route to a much greater extent than do passerine long-distance migrants.

25-year study of the population development of central European songbirds: A general decline most evident in long-distance migrants

During the past century a decline hasbeen noted in European bird popula-tions, both in large species [1] andpossibly also in songbirds [2]. Todaythe “Red List” (of endangered spe-cies) includes about 50% of the avi-fauna in most Central Europeancountries; about 30% of species aredeclining to an extent that threatenstheir continued existence in CentralEurope. These include songbirds,mainly open-country species that areeasy to monitor. Trends in the num-bers of many unobtrusive songbirdspecies, however, have remainedlargely unclear [3]. To assess theirpopulation changes our institute be-gan a census program in 1972 with thehelp of hundreds of amateur ornitho-logists [4]. A trapping station in thisproject in southern Germany has pro-vided data on 35 species over 25 years– the first dataset based on strictlystandardized methods over such along period. During this entire periodthe number of trapped birds has fall-en slowly but continuously, by an av-erage of about 1% per year. The de-crease is greatest for long-distancemigrants, and it heralds profoundchanges in the Central European avi-fauna.Populations of large birds such as ea-gles and storks can be determined ac-curately, and most of the Europeanbreeding pairs are monitored. Forspecies that are more common or areharder to observe, such as crows andowls, only rough estimates are possi-ble [3]. Serious problems are encoun-tered in songbirds. Abundant, widelydistributed, and unobtrusive speciescannot be counted completely or di-rectly; regional estimates must bebased on indirect procedures such asrecording territorial song. Such esti-mates are often biased by varying,nonquantifiable “observer quality”[5]. Therefore only a few countrieshave established sufficiently reliableprograms for monitoring songbirdsduring the breeding period [6, 7].In 1968 we began testing standardizedtrapping procedures for monitoringsongbird populations in order to re-duce differences among observers bya more objective method. The resultswere positive [8], and in 1972 wetherefore initiated the “Mettnau-Reit-Illmitz” program (based onthree stations, Mettnau in southernGermany, Reit in northern Germany,and Illmitz in Austria. This programwas later extended, and temporarilygrew into an ESF network encom-passing Europe and Africa [9]). TheMettnau station has operated sincethe outset, and we report here on theresults of a full quarter of a century ofsongbird population monitoring.The samples are obtained by trappingpassage migrants during the autumnmigration while staging at rest sites.A suitable study area must (a) becharacterized by largely unchangingvegetation, (b) include different habi-tats so that birds with different eco-logical requirements can rest there,and (c) be a protected area of guaran-teed long-term existence. The Mett-nau peninsula, with a 50-year-old birdsanctuary, is ideal for the purpose[10]. The 35 songbird species selectedfor monitoring include regularly stag-ing long-, intermediate-, and short-distance migrants (Table 1).The birds are trapped in nylon netsnormally used to catch birds for ring-ing; 2 m high and 7 m long, they areset up between wooden bars on poles.A wall is formed by 52 nets extendingthrough 8 different habitats (from abrush zone through forested and wetregions). The annual trapping periodis June 30–November 6 and includesthe entire autumn migratory periodof songbirds in Central Europe. Thenets are checked hourly from dawnuntil soon after dusk; trapped birdsare ringed (to prevent double count-ing), subjected to biometric tests andthen released. The monitoring condi-tions (annual setting up of the nets,collecting the birds, data collection,etc.) are standardized as far as possi-ble [10]. Most of the investigatedbirds come from Central Europe, al-though some have traveled fromnorthern, eastern, and western Eu-rope, and a small proportion are localbreeding birds. These origins areknown from recoveries of ringed indi-viduals [11] and from biometric dataon population differentiation [10].Test studies have confirmed thatstandardized trapping procedures ef-fectively give reliable estimates ofsongbird populations. Safriel andLavee (1991) showed that the numberof palaearctic songbird migrants trap-ped in Sinai is correlated positivelywith estimates of their European pre-migratory population sizes [12]. Dunnet al. (1997) demonstrated that trendsin the annual capture indices of song-birds trapped during autumn migra-tion in Michigan are correlated posi-tively with trends in breeding birdsurvey data from their breedinggrounds and conclude that “intensivestandardized netting can be a usefulpopulation monitoring tool” [13]. Wehave consistently found that trends intrapping data reliably reflect thosefrom other sources such as single-spe-cies population studies and country-wide population estimates for RedLists, etc. [4]. Thus data from 147,661individuals that were caught at Mett-nau between 1972 and 1996 reflectthe population development of 35Central European songbird species,as follows.

All across Africa: highly individual migration routes of Eleonora's falcon.

Eleonoras falcon (Falco eleonorae) is a rare raptor species that delays its breeding period until late summer to feed its young with passerines at the peak of autumn migration. Since the 1950s, this slender winged falcon has been believed to migrate along a historical route via the Red Sea to its main wintering area in Madagascar. In our study, we used satellite telemetry to investigate the real migration route of Eleonoras falcons and found that the species displayed a highly individual migration pattern. Furthermore, juvenile falcons migrated via West Africa to Madagascar and two juveniles could be tracked during spring migration and to their summering areas in East and West Africa. As juveniles migrated independently of adults, we discuss inherited navigation strategies forming part of a complex navigation system. We propose the idea of an orientation mechanism that naive falcons could apply during their long-distance migration towards their faraway wintering area located in the open ocean.

Steuerung und potentielle Evolutionsgeschwindigkeit des obligaten Teilzieherverhaltens: Ergebnisse eines Zweiweg-Selektionsexperiments mit der Mönchsgrasmücke (Sylvia atricapilla)

1. In Südfrankreich lebt eine obligat teilziehende Population der Mönchsgrasmücke (Sylvia atricapilla) mit rund drei Vierteln Zugvögeln und einem Viertel Standvögeln. Das Teilzugverhalten dieser Population wird in beträchtlichem Umfang von genetischen Faktoren gesteuert (Berthold &Querner 1982). Der starke Selektionserfolg eines Zweiweg-Selektionsexperiments bis zur F1-Generation ließ eine hohe potentielle Evolutionsgeschwindigkeit des obligaten Teilzieherverhaltens vermuten (2). Wir haben das Evolutionspotential in einem Langzeit-Selektionsversuch experimentell untersucht. 2. Wir zogen insgesamt 267 Individuen der freilebenden Mönchsgrasmückenpopulation in fünf Gruppen von Hand auf, und alle fünf Stichproben zeigten entsprechende Verhältnisse von Ziehern und Nichtziehern. Wir konnten das Langzeit-Zweiweg-Selektionsexperiment bis zu einer F6-Generation durchführen und konnten dabei insgesamt 455 Mönchsgrasmücken in Volieren züchten. 3. Das Zweiweg-Selektionsexperiment zeigt, daß die untersuchte teilziehende Mönchsgrasmückenpopulation bereits nach drei Generationen eine ausschließlich ziehende und nach vier bis sechs Generationen eine fast nicht mehr ziehende Population werden kann. 4. Das Zweiweg-Selektionsexperiment zeigt starken Selektionserfolg und hohe Heritabilitätswerte (ca. 0,6–1), die deutlich höher liegen als bisher für das Verhalten von (meist domestizierten) Wirbeltieren angegeben. Demnach sind genetische Faktoren für die Steuerung dieses obligaten Teilzugs sehr bedeutsam und wahrscheinlich dominant über Umwelteinflüsse. 5. Die Versuchsergebnisse lassen im Falle von schnellen Umweltveränderungen und der Wirkung von starken Selektionsfaktoren ein enorm großes Evolutionspotential des obligaten Teilzieherverhaltens annehmen und damit allgemein eine schnelle Mikroevolution der Ortsbewegung von Vögeln. Sollten die von Meteorologen prophezeiten Klimaänderungen in Bälde eintreten (Erwärmung aufgrund von Verunreinigungen der Atmosphäre durch den Menschen, „Treibhauseffekt”), dann könnten viele obligate Teilzieher auf genetischer Basis rasch zu Standvögeln werden und wenig ausgeprägte Zieher rasch zu Teilziehern. Unter diesem allgemeinen Anwachsen von Standvögeln könnten ausgeprägte Zugvögel mehr und mehr zu leiden haben. 6. Eine genetische Kontrolle obligaten Teilzugs scheint weit verbreitet zu sein, und sie stellt wohl auch für alle Individuen den zuverlässigsten Steuerungsmechanismus dar. Beim fakultativen Teilzug hingegen dürften Umweltfaktoren mehr unmittelbar steuernd wirken. 1. In southern France breeds an obligate partially migratory population of the Blackcap with about three quarters of migrants and one quarter of residents. Partial migration of this population is considerably controlled by genetic factors (Berthold &Querner 1982). The large selection response of a two-way selective breeding experiment up to F1-generations suggested a high evolutionary potential of obligate partial migration (2). We have this evolutionary potential experimentally investigated in a long-term selective breeding study. 2. We raised by hand a total of 267 individuals of the free-living Blackcap population in five groups, and all five samples showed corresponding ratios of migrants and nonmigrants. We were able to conduct the long-term selective breeding experiment up to a F6-generation, and thereby a total of 455 Blackcaps could be bred in aviaries. 3. The two-way selective breeding experiment shows, that the investigated partially migratory Blackcap population can become completely migratory in just three generations and almost exclusively sedentary in just four to six generations. 4. The two-way selective breeding experiment yielded large selection responses and high heritability values (about 0.6–1) which are distinctly higher than those previously reported for behavioural traits of (mostly domesticated) vertebrates. Hence, genetic factors are very important for the control of this obligate partial migration and are presumedly dominant over environmental influences. 5. In case of rapid environmental changes and the effect of strong selection factors the experimental results suggest a strikingly high evolutionary potential of obligate partial migration and thus in general a rapid microevolution of bird movements. If climatic changes would occur in the near future as they are predicted by meteorologists (rise in temperature due to man-made pollution of the atmosphere, “greenhouse-effect”) then many obligate partial migrants could rapidly become sedentary on a genetic basis and many less typical migrants could then considerably suffer from the general increase of residents. 6. A genetic control of obligate partial migration appears to be widespread and it also appears to be the most reliable control mechanism for all individuals of such a partially migratory population. Facultative partial migration, however, appears to be controlled more directly by environmental factors.

Satellite tracking of Cory's Shearwater migration

Abstract Transmitters were attached to four adult male Corys Shearwaters (Calonectris diomedea) caught at their breeding sites off Crete, Greece, in autumn 1998. The birds had left the Mediterranean by the beginning of December. Two were last recorded in the eastern tropical Atlantic in January/February. The other two wintered east of the Mid-Atlantic Ridge, one at about 10°N, the other one in equatorial waters, and could be tracked until return migration in March/April. The seasonal variation in travel speed is in accordance with a conventional pattern of migration with phases of migration and wintering, rather than continuous movement throughout the nonbreeding cycle. The birds left the Mediterranean later and wintered farther north than expected. We suggest that the known longitudinal cline in body size, morphology, and vocalizations of Corys Shearwater may also be found in migration behavior.

Long-term satellite tracking sheds light upon variable migration strategies of White Storks (Ciconia ciconia)@@@Langzeit Satelliten-Telemetrie beim Weißstorch gibt Hinweise auf variable Zug- und Überwinterungsstrategien

During investigations on the migration of 120 individual White Storks by means of satellite tracking, four birds were tracked into their winter quarters several times, one bird on nine successive journeys. These storks did not exhibit strong winter-site fidelity, but instead occupied somewhat different winter quarters from one year to the next, probably depending on the food supply. Bisher konnten wir 120 Weißstörche auf ihrem Zug mit Hilfe der Satelliten-Telemetrie verfolgen, 4 Vögel mehrfach und einen auf neun aufeinander folgenden Wanderungen. Dabei zeichnet sich ab, dass Weißstörche im Gegensatz zu vielen anderen Afrikaziehern nur geringe Winterquartiertreue zeigen und im Laufe von Jahren in verschiedenen Gebieten überwintern, wahrscheinlich in Abh ängigkeit vom Nahrungsangebot.

Was Zugunruhe wirklich ist — eine quantitative Bestimmung mit Hilfe von VideoAufnahmen bei Infrarotlichtbeleuchtung

In 9 hand-raised Garden Warblers, Zugunruhe was continuously recorded in registration cages with movable perches on microswitches in a constant 12:12 hr light-dark cycle throughout the first fall migratory period. In addition, video-records were taken during 23 nights under infrared illumination involving more than 150 hours. The main results are: (1) infrared illumination did not affect Zugunruhe or other events and thus is a useful method, (2) over 90 % of the Zugunruhe recorded with video is wing whirring (i. e. intense wing beating in a sitting position), the rest is hopping and flying, (3) an interval of the customarily used “half-an-hour-with-Zugunruhe” equals 14.1 min of wing whirring, (4) 35.9 % of the Zugunruhe recorded as wing whirring is missed in a registration cage with one movable perch. This loss is reduced to about 5 % if two movable perches are used, (5) the experimental birds produced in the average 352.1 ± 170.51 (SD) “hours with Zugunruhe” which equals about 165 hrs of wing whirring. When this value is multiplied by the average flight speed of the species during migration (about 25–30 km/h) a theroretical flight distance of about 4800 km is obtained. This is just the distance from the south German breeding grounds via Spain to the estuary of the river Niger which is situated within the center of the population-specific winter quarters. Zugunruhe in that species thus appears with some restrictions to be “wandering by wing whirring in a sitting position”.

Satelliten-Telemetrie beim Weißstorch (Ciconia ciconia) auf dem Wegzug — eine Pilotstudie

(1) 1991 konnten erstmals 4 mit Kleinsendern ausgerüstete Weißstörche mit Hilfe der Satelliten-Telemetrie auf Teilstrecken ihres Wegzugs bis zu 46 Tage lang verfolgt werden. Die japanischen Sender betrugen nur etwa 2 % des Körpergewichts der Vögel; die Ortung erfolgte durch das ARGOS-System. Die Versuchsvögel zeigten völlig normales Zugverhalten. — (2) Drei der in Brandenburg und Sachsen-Anhalt markierten Vögel waren Ostzieher und konnten über Strecken von etwa 640–4700 km verfolgt werden, 1 Storch bis zur ägyptisch-sudanesischen Grenze. Ein Westzieher konnte rund 1400 km bis zu den Pyrenäen geortet werden. — (3) Die Vögel wanderten individuell recht verschieden. 2 zogen weitgehend kontinuierlich bis in den Sudan bzw. zu den Pyrenäen, die anderen legten längere Pausen ein. Die ermittelten Zugstrecken verliefen recht geradlinig; Richtungsänderungen erfolgten vor allem an der Donau, den Karpaten, am Mittelmeer und auf der Sinai-Halbinsel. Tagesetappen betrugen mindestens bis zu 370 km, in einem Fall in 21 Tagen durchschnittlich 224 km/Tag. Die Zuggeschwindigkeit lag in der Größenordnung von 30–90 km/h. — (4) Verbesserte Sender mit längerer Lebensdauer und mehreren Ortungen pro Tag dürften es bald ermöglichen, individuelle Wanderrouten von Weißstörchen und anderen Großvögeln praktisch lückenlos zu ermitteln. Begleitmannschaften werden zudem die Zug- und Rastökologie mit Sendern ausgerüsteter Vögel mit erfassen können. Damit dürfte der Vogelschutz auf dem Zug eine neue Dimension gewinnen. (1) In 1991 parts of the routes of White Storks migrating in autumn could be recorded for the first time by satellite tracking. Four individuals could be followed for up to 46 days. Transmitter weight accounted for only about 2 % of body mass. Locations were obtained by the ARGOS system. Migratory behaviour of the experimental birds appeared to be absolutely normal. — (2) The birds were equipped with transmitters in eastern Germany. Three of them followed the eastern migration route and could be tracked from 640 up to 4700 km, the latter reaching the borders of Egypt and Sudan. A western migrant could be followed over a distance of about 1400 km towards the Pyrenees. — (3) Migration showed considerable individual variation. Whereas in two birds migration was largely continuous towards the Sudan and the Pyrenees, respectively, the other birds rested for longer periods. The tracked migration routes were fairly straight. Marked directional shifts occurred towards the Danube valley, at the Carpathian mountains, the Mediterranean and on the Sinai. Capacity per day was at least 370 km. One bird covered 224 km/day on average during a period of 21 days. Migration speed ranged in the magnitude of 30–90 km/h. — (4) Improved transmitters with increased lifetime giving several locations per day will presumably allow to record migration routes of White Storks and other large birds more completely in the near future. Escorts should then be able to closely analyse the ecology of migration and staging of their test birds. These possibilities may give a new dimension to bird conservation measures during migration.

Der Zug des Weißstorchs (Ciconia ciconia): eine besondere Zugform auf Grund neuer Ergebnisse

To formulate a comprehensive plan for the conservation of the White Stork (Ciconia ciconia) in conformity with the “Bonn Convention”, along the eastern migration route from the breeding grounds across Israel into the staging areas in northeastern Africa, it was essential to investigate the entire process of migration, including resting behaviour as well as the energetic and ecological aspects. Our approach employed satellite tracking (of 75 individuals), observations of storks in aviaries by methods including magnetic resonance imaging (MRI) and spectroscopy (MRS) (12 birds over 15 months), and extensive field studies. The main result of the investigation is that the White Stork exhibits, at least on the eastern route, a particular mode of migration not previously described in this form for any bird species, with the following characteristics: (i) very rapid travel from the breeding region into the North African staging areas, normally with flight periods every day, lasting about 8–10 hours and separated by 14–16 hours of rest. The ca. 4600-km distance to latitude 18°N is covered in an average of 18–19 days by both young and adult storks. (ii) Rest periods of a whole day or even several days are the exception, and their occurrence seems to be prompted by external circumstances rather than prescribed in the endogenous migration program. (iii) Body mass and fat deposition are low during the outward (and the homeward) journey and peak in midwinter, which is interpreted as an adaptation to unpredictable conditions in the winter quarters. (iv) There is no discernible hyperphagia during migration; instead, on the outward journey the storks evidently feed mainly to meet their immediate needs when in eastern Europe, more opportunistically when approaching the Mediterranean Sea, and practically not at all in Israel. According to this observation and the comparison of body weights in Sachsen-Anhalt and Israel, it is likely that storks lose weight on the outward trip and do not regain it until they reach Africa. We call the migration mode of the White Stork, which travels predominantly in gliding flight, the MSOM type (from “mostly travelling every day”, “seldom inserting whole-day rests”, “opportunistically feeding” and “moderate or no fat depots developing”), and distinguish it from the types ILHB (for intermittently migrating) and NNHB (migrating non stop) (see Discussion). The results of this study, in particular regarding fat deposition and state of breast musculature, are based substantially on MRI and MRS; these methods, tested here in a pioneering long-term study of a bird species living in the wild, have proved extremely useful and show great promise (see following paper). Für ein umfassendes Schutzkonzept für den Weißstorch (Ciconia ciconia) im Rahmen der „Bonner Konvention“ entlang der Ostroute von den Brutgebieten über Israel bis in nordostafrikanische Zwischenziele war es erforderlich, den genauen Zugablauf, das Rastverhalten sowie Fragen der Zugenergetik und Zugökologie zu untersuchen. Wir bearbeiteten die Fragen mit Hilfe der Satelliten-Telemetrie (75 Individuen), der Untersuchung von Störchen in Volieren einschließlich der Magnet-Resonanz-(MR-)Tomographie und -Spektroskopie (MRS) (12 Vögel, über 15 Monate) sowie umfangreicher Freilandstudien. Das Hauptergebnis der Untersuchungen ist: Der Weißstorch zeigt — zumindest auf der Ostroute — einen eigenartigen, bisher von keiner anderen Vogelart in dieser Form beschriebenen Zugmodus mit folgenden Charakteristika: 1) sehr zügiges, normalerweise tagtägliches Wandern vom Brutgebiet bis in die nordafrikanischen Zwischenziele, wobei täglich etwa 8–10 Stunden gewandert und 14–16 Stunden gerastet wird. Die rund 4 600 km bis zum 18. Breitengrad werden von Jung- wie Altstörchen im Mittel in 18–19 Tagen bewältigt. 2) Ganz- oder gar mehrtägige Rast wird nur ausnahmsweise eingeschoben und scheint eher durch äußere Umstände erzwungen als im endogenen Zugprogramm vorgegeben zu sein. 3) Körpermasse und Fettdeposition sind während des Wegzugs (und des Heimzugs) niedrig und erreichen Gipfelwerte im Mittwinter, die als Anpassung an unvorhersagbare Bedingungen im Winterquartier gedeutet werden. 4) Zugzeitliche Hyperphagie ist nicht erkennbar, vielmehr nehmen Störche während des Wegzugs Nahrung in Osteuropa wohl v. a. zur Deckung des Unterhaltsbedarfs auf, zum Mittelmeer hin mehr opportunistisch und in Israel so gut wie gar nicht. Dadurch und aus dem Vergleich von Körpermassen in Sachsen-Anhalt und Israel wird wahrscheinlich, dass Störche auf dem Wegzug an Masse verlieren, die dann erst in Afrika wieder aufgefüllt wird. Wir bezeichnen den Zugmodus des überwiegend im Gleitflug wandernden Weißstorchs als MSOM-Typ (von „Meist täglich wandernd“, „Selten ganze Rasttage einlegend“, „Opportunistisch Nahrung aufnehmend“ und „Maximal Mittelmäßige Fettdepots bildend“) und stellen ihm die Typen ILHB (für intermittierend ziehend) sowie NNHB (nonstop wandernd) gegenüber (s. Diskussion). Die Ergebnisse dieser Arbeit, v. a. über Fettdeposition und Brustmuskelzustand, beruhen ganz wesentlich auf der MR-Tomographie und MR-Spektroskopie, die hier in einer Lang-zeit-Pilotstudie an einer wild lebenden Vogelart zum Einsatz kam und sich als sehr nützlich und vielversprechend erwies (s. die nachfolgende Arbeit).