Martins Briedis

Barrier crossing in small avian migrants: individual tracking reveals prolonged nocturnal flights into the day as a common migratory strategy

Over decades it has been unclear how individual migratory songbirds cross large ecological barriers such as seas or deserts. By deploying light-level geolocators on four songbird species weighing only about 12u2009g, we found that these otherwise mainly nocturnal migrants seem to regularly extend their nocturnal flights into the day when crossing the Sahara Desert and the Mediterranean Sea. The proportion of the proposed diurnally flying birds gradually declined over the day with similar landing patterns in autumn and spring. The prolonged flights were slightly more frequent in spring than in autumn, suggesting tighter migratory schedules when returning to breeding sites. Often we found several patterns for barrier crossing for the same individual in autumn compared to the spring journey. As only a small proportion of the birds flew strictly during the night and even some individuals might have flown non-stop, we suggest that prolonged endurance flights are not an exception even in small migratory species. We emphasise an individual’s ability to perform both diurnal and nocturnal migration when facing the challenge of crossing a large ecological barrier to successfully complete a migratory journey.

Cold spell en route delays spring arrival and decreases apparent survival in a long-distance migratory songbird

BackgroundAdjusting the timing of annual events to gradual changes in environmental conditions is necessary for population viability. However, adaptations to weather extremes are poorly documented in migratory species. Due to their vast seasonal movements, long-distance migrants face unique challenges in responding to changes as they rely on an endogenous circannual rhythm to cue the timing of their migration. Furthermore, the exact mechanisms that explain how environmental factors shape the migration schedules of long-distance migrants are often unknown.ResultsHere we show that long-distance migrating semi-collared flycatchers Ficedula semitorquata delayed the last phase of their spring migration and the population suffered low return rates to breeding sites while enduring a severe cold spell en route. We found that the onset of spring migration in Africa and the timing of Sahara crossing were consistent between early and late springs while the arrival at the breeding site depended on spring phenology at stopover areas in each particular year.ConclusionUnderstanding how environmental stimuli and endogenous circannual rhythms interact can improve predictions of the consequences of climate changes on migratory animals.

Year-round spatiotemporal distribution of the enigmatic Semi-collared Flycatcher Ficedula semitorquata

AbstractWe examined migration routes and non-breeding sites of a poorly studied long-distance migrant, the Semi-collared Flycatcher Ficedula semitorquata, by tracking adult birds with geolocators from an eastern European breeding population across two subsequent years. All 11 birds migrated in a clockwise loop fashion where autumn migration routes lay east from the spring migration routes. Non-breeding sites were located in Eastern-Central Africa, i.e. Uganda, Tanzania, Burundi, Rwanda, and east DR Congo, where birds spent on average 128xa0days. Non-breeding sites of two birds were located outside of the currently estimated species’ non-breeding range.ZusammenfassungRäumlich-zeitliche Verbreitung des wenig bekannten HalbringschnäppersFicedula semitorquataim Jahresgangn Wir bestimmten Zugwege und Überwinterungsgebiete eines wenig bekannten Langstreckenziehers, des Halbringschnäppers Ficedula semitorquata. Mit Hilfe von Geolokatoren verfolgten wir adulte Vögel einer osteuropäischen Population während zweier aufeinanderfolgender Jahre. Alle 11 Halbringschnäpper zogen schleifenförmig im Uhrzeigersinn mit einer östlicheren Herbstzugroute und einer mehr westlichen Frühlingszugroute. Die Überwinterungsgebiete lagen im östlichen Zentralafrika (östlicher Teil der Republik Kongo) und Ostafrika (Uganda, Tansania, Burundi, Ruanda). Die Vögel verbrachten durchschnittlich 128xa0Tage im Überwinterungsgebiet. Zwei Vögel überwinterten ausserhalb des bisher angenommen Verbreitungsgebietes der Art.

Annual cycle and migration strategies of a habitat specialist, the Tawny Pipit Anthus campestris, revealed by geolocators

AbstractHabitat specialist species occupy narrow ecological niches, typically utilizing similar habitat types throughout the annual cycle. Their strict requirements for specific habitats may make them vulnerable to environmental changes, especially in small, local populations. Therefore, detailed knowledge of the species’ ecology is crucial for conservation purposes. In this study, we used light-level geolocators to identify migration routes and non-breeding areas of a distinct specialist for dry habitats, the Tawny Pipit Anthus campestris, from a currently declining central European breeding population. During autumn and spring migration, the majority of the birds followed a route along the northwest of the Alps and via the Iberian Peninsula, with stopover sites mainly in northern Africa. In each migration season, however, one of two different individuals took a detour around the eastern side of the Alps. When crossing the main ecological barrier, the Sahara Desert, three of six birds followed the Atlantic coastline in autumn, whereas all five birds migrated near the coast in spring. Non-breeding areas of all tracked pipits were uniformly located in the Western Sahel, with five of six birds utilizing two main non-breeding sites, the second of which was always located west of the first. On average, the tracked birds spent 48xa0% of the year at the non-breeding areas, 27xa0% on migration, and 25xa0% at the breeding site. Our findings demonstrate strong migratory connectivity in Tawny Pipits which may have future implications for conservation of this long-distance migrant.ZusammenfassungJahreszyklus und Zugstrategien des Brachpiepers als Habitatspezialisten mit Hilfe von Geolokatoren offengelegtn Habitatspezialisten weisen enge ökologische Nischen auf und nutzen während des gesamten Jahres weitestgehend ähnliche Habitate. Solch ein enger Anspruch an einen Habitattyp könnte die betreffende Art, insbesondere kleine, lokale Populationen, angreifbar für Umweltveränderung machen. Ein fundiertes Wissen zur Ökologie solcher Arten ist demnach ausschlaggebend für gezielte Schutzmassnahmen. In der vorliegenden Studie verwendeten wir Geolokatoren, um die Zugrouten und Aufenthaltsgebiete außerhalb der Brutzeit des an Trockenhabitate gebundenen Brachpiepers Anthus campestrisxa0zu identifizieren, die aus einer rückläufigen mitteleuropäischen Brutpopulation stammten. Die Mehrzahl der Vögel nutzte auf dem Herbst- und Frühlingszug eine Flugroute nordwestlich der Alpen über die Iberische Halbinsel mit Rastplätzen in Nordafrika. Jedoch flog in jeder Zugsaison ein jeweils anderes Individuum einen Umweg um die Alpen östlich zu umgehen. Die Sahara als grosse ökologische Barriere wurde im Herbst von drei der sechs Vögel entlang der Atlantik-Küste überquert, während im Frühling alle Vögel diesen Weg nahmen. Alle untersuchten Pieper überwinterten in der westlichen Sahelzone. Fünf der sechs Vögel nutzten dabei zwei getrennte Überwinterungsplätze, wobei der zweite Aufenthaltsort jeweils westlich vom ersten lag. Die untersuchten Pieper verbrachten 48xa0% des Jahres in ihrem Überwinterungsquartier, 27xa0% auf dem Zug und 25xa0% der Zeit am Brutplatz. Unsere Ergebnisse belegen für den Brachpieper eine starke Zugkonnektivität, die Konsequenzen für zukünftige Schutzmaßnahmen haben könnte.

Red-spotted Bluethroats Luscinia s. svecica migrate along the Indo-European flyway: a geolocator study

Capsule Red-spotted Bluethroats Luscinia s. svecica from two European breeding populations spent the boreal winter on the Indian sub-continent. Aim Tracking the migration of Red-spotted Bluethroats from Europe to the hitherto unknown non-breeding areas and back. Methods Light-level geolocators were deployed on male Bluethroats at breeding sites in the Czech Republic (nu2009=u200910) and in Norway (nu2009=u200930). Recorded light intensity data were used to estimate the locations of non-breeding sites and migration phenology during the annual cycle. Results Bluethroats spent the boreal winter in India (nu2009=u20093) and Pakistan (nu2009=u20091), on average more than 6000u2005km from their breeding areas. Autumn migration started in August (nu2009=u20091) or early September (nu2009=u20092), and lasted for 26–74 days. Spring migration commenced on 8 and 9 April (nu2009=u20092) and lasted for about a month. During both autumn and spring migration, birds stopped over two or three times for more than 3 days. Conclusion This study for the first time showed where Red-spotted Bluethroats from European breeding populations stay during the boreal winter. This seems to be the first time that a passerine bird has been tracked along the Indo-European flyway.

Linking events throughout the annual cycle in a migratory bird—non-breeding period buffers accumulation of carry-over effects

Annual cycles of animals consist of distinct life history phases linked in a unified sequence, and processes taking place in one season can influence an individual’s performance in subsequent seasons via carry-over effects. Here, using a long-distance migratory bird, the collared flycatcher Ficedula albicollis, we link events throughout the annual cycle by integrating breeding data, individual-based tracking, and stable-carbon isotopes to unravel the connections between different annual phases. To disentangle true carry-over effects from an individuals’ intrinsic quality, we experimentally manipulated the brood size of geolocator-tracked males prior to tracking. We did not find unambiguous differences in annual schedules between individuals of reduced and increased broods; however, in the following spring, the latter crossed the Sahara and arrived at the breeding grounds earlier. Individuals with higher absolute parental investment delayed their autumn migration, had shorter non-breeding residency period but advanced spring migration compared to individuals with lower breeding effort. Neither the local non-breeding conditions (as inferred from δ13C values) nor the previous breeding effort was linked to the timing of the following breeding period. Furthermore, while on migration, collared flycatchers showed a pronounced “domino effect” but it did not carry over across different migration seasons. Thus, the non-breeding period buffered further accumulation of carry-over effects from the previous breeding season and autumn migration. Our results demonstrate tight links between spatially and temporally distinct phases of the annual cycles of migrants which can have significant implications for population dynamics.Significance statementTiming is everything! This holds true also for migratory animals which must time their annual movements, breeding and non-breeding seasons according to the environment they live in. However, perfect timing of a particular event can be hampered by past events. We studied connections between spatially and temporarily distinct annual phases in collared flycatchers, a small bodied bird which twice a year migrates between Europe and sub-Saharan Africa. We found tight links between individual’s parental investment and timing of autumn migration, but not spring migration. Similarly, the timing of autumn migration did not translate to influence the timing of spring migration. Thus, our results demonstrate that the non-breeding period may serve as a buffer to overcome high energy expenditure during the previous breeding season and prevent further accumulation of carry-over effects in migratory birds.

Extracting historical population trends using archival ringing data—an example: the globally threatened Aquatic Warbler

Understanding how animal population size changes over time is one of the key means to identify threats and facilitate the successful implementation of conservation measures. The globally endangered Aquatic Warbler has undergone a major decline throughout its range. While in the first half of the 20th century, it was still an abundant species across major parts of Central and Western Europe, over the last century the size of its European population is considered to have declined by more than 90xa0%. However, little is known of the historical changes in its population size. Here we model the past population size of the Aquatic Warbler using historical ringing records of European ringing schemes and population monitoring software (TRends for Indices and Monitoring). We found that during the short 30-year period between 1950 and 1980 the European Aquatic Warbler population underwent a dramatic 95xa0% decline. According to this model, the population has recently been stable, no further decline was observed between 1980 and the late 1990s.ZusammenfassungRekonstruktion früherer Populations-Trends anhand archivierter Beringungsdaten am Beispiel des weltweit bedrohten Seggenrohrsängers (Acrocephalus paludicola) Zu wissen, wie sich die Größen von Populationen über die Zeit verändern, ist im Naturschutz entscheidend wichtig für das Verstehen zukünftiger Bedrohungen und für Entscheidungen, mit welchen Maßnahmen man erfolgreich gegen sie vorgehen kann. Die Bestände des weltweit bedrohten Seggenrohrsängers gehen auf breiter Front zurück. In der ersten Hälfte des 20. Jahrhunderts gab es noch Populationen in weiten Bereichen Zentral- und Westeuropas, aber im letzten Jahrhundert sind die Populationen um mehr als 90xa0% zurückgegangen, wobei über die früheren, historischen Veränderungen der Populationsgrößen jedoch nur sehr wenig bekannt ist. In unserer Untersuchung modellierten wir frühere Populationsgrößen des Seggenrohrsängers mit Hilfe alter Beringungsdaten europäischer Beringungsprojekte und einer für Populationsuntersuchungen erstellten Software (TRends for Indices and Moniotoring—TRIM). Wir haben festgestellt, dass die europäische Population des Seggenrohrsängers nur allein in den 30 Jahren von 1950 bis 1980 um dramatische 95xa0% zurückgegangen ist. Das Modell zeigt ferner, dass sich die Population in letzter Zeit stabilisiert hat; zwischen 1980 und den späten 1990er Jahren konnte kein weiterer Rückgang mehr beobachtet werden.

Loop migration, induced by seasonally different flyway use, in Northern European Barn Swallows

AbstractSeasonal variation in migratory routes seems to be a common trait among many Afro-Palearctic migrants, but there are only few examples of species or populations which shift between entirely different flyways in autumn and spring. To identify non-breeding regions and seasonal differences in migration strategies we tracked Barn Swallows (Hirundo rustica) from a Baltic breeding population by light-level geolocators. Using novel analytical tools, we provide the first full annual tracks for European swallows. The main non-breeding residency sites of the tracked individuals were located in Southern Africa and all birds followed a distinct counterclockwise loop migration pattern shifting from the central Afro-Palearctic flyway in autumn to the eastern Afro-Palearctic flyway in spring. Despite the elongated detour through the Arabian Peninsula and the Caucasus Mountains, spring migration was faster than autumn migration in all of the tracked males and one out of two females, implying favorable conditions en route that allow for more efficient and faster traveling.ZusammenfassungSchleifenzug nordeuropäischer Rauchschwalben, hervorgerufen durch jahreszeitlich unterschiedliche Zugroutenn Saisonal unterschiedliche Migrationsrouten scheinen bei vielen afro-paläarktischen Zugvögeln aufzutreten. Es gibt jedoch nur wenige Beispiele, bei denen eine Art oder eine Population völlig verschiedene Flugrouten im Herbst und im Frühjahr nutzt. Wir untersuchten baltische Rauchschwalben (Hirundo rustica) mittels Geolokatoren, um ihre Überwinterungsgebiete und saisonale Zugstrategien zu identifizieren. Die Hauptüberwinterungsorte der untersuchten Schwalben lagen im südlichen Afrika. Alle Vögel zeigten ein gegen den Uhrzeigersinn gerichtetes Zugmuster mit einer zentralen paläarktisch-afrikanischen Zugroute im Herbst und einer östlichen afro-paläarktischen Route im darauffolgenden Frühjahr. Der Frühjahrszug war trotz des langgezogenen Umwegs über die Arabische Halbinsel und den Kaukasus bei allen untersuchten Männchen und bei einem der beiden Weibchen schneller als der Herbstzug. Dies deutet auf sehr günstige Umweltbedingungen hin, die einen effizienteren und schnelleren Zugablauf ermöglichten.

Haemosporidian blood parasite diversity and prevalence in the semi-collared flycatcher (Ficedula semitorquata) from the eastern Balkans.

We present the first survey on prevalence and diversity of haemosporidian parasites of the genera Plasmodium and Haemoproteus in a poorly studied migratory passerine, the semi-collared flycatcher (Ficedula semitorquata). In total, 110 individuals were sampled during two breeding seasons in Eastern Bulgaria. We collected both blood samples for PCR identification and blood films for microscopic identification of haemosporidians. We found six distinctive parasite cyt b lineages present in the blood of the semi-collared flycatcher (three Haemoproteus and three Plasmodium). Two of the lineages, i.e. pWW3 of Plasmodium sp. and hCCF2 of Haemoproteus sp., are recorded for the first time in the family Muscicapidae. The overall prevalence ranged between 12.2 and 15.9% and we did not find co-infections. We hypothesize that the low prevalence of haemosporidians in this species might be linked to its small population size and relatively restricted geographical range.

Migration, wing morphometry and wing moult in Spanish and House Sparrows from the eastern Balkan Peninsula

AbstractOn the Balkan Peninsula, migratory Spanish Sparrows breed sympatrically with resident House Sparrows. While the two species share many biological and ecological traits, migratory patterns and adaptions to migratory lifestyle of the Spanish Sparrow are unknown. We tracked a Spanish Sparrow across its 1800xa0km long migration from Bulgaria to the nonbreeding sites in the Nile Delta. Stopovers were situated in western Turkey, before and after the 12xa0h-nonstop flights across the Mediterranean Sea. We show similar wing morphology in Spanish and House Sparrows indicating little adaptation to migration. However, Spanish Sparrows moult primaries earlier and faster allowing for timely migratory departure.ZusammenfassungZug, Flügelmorphometrie und Flügelmauser von Weiden- und Haussperlingen der östlichen Balkan-Halbinseln Auf der Balkanhalbinsel brüten Weidensperlinge sympatrisch mit residenten Haussperlingen. Beide Arten teilen viele biologische und ökologische Merkmale; Zugmuster und Anpassungen an das Zugverhalten sind für den Weidensperling jedoch noch weitgehend unbekannt. Wir beschreiben hier die 1800xa0km lange Wanderung eines Weidensperlings von Bulgarien bis in das ägyptische Winterquartier im Nildelta. Der Vogel rastete im Herbst und im Frühling in der Westtürkei, vor bzw. nach seinem 12-stündigen Nonstop-Flug über das Mittelmeer. Weidensperlinge der Balkanhalbinsel hatten die gleiche Flügelmorphologie wie Haussperlinge und zeigten somit eine geringe Anpassung an den Zug. Sie mauserten ihre Flügelfedern jedoch zeitiger und schneller als diexa0lokalen Haussperlinge und können somit zeitig im Herbst abwandern.