Notes sobre la fenologia i selecció de l'hàbitat de la baldritja de les Balears Puffinus mauretanicus

La baldritja de les Balears Puffinus mauretanicus és present en nombres importants a la costa catalana. Aquesta presència coincideix amb l'època de màxima productivitat biològica del mar Balear. Es distribueix principalment per les aigües de la plataforma continental, on pesca de manera activa a poca distància de la costa. Sovint forma grans estols sobre moles de peix, principalment a la tardor i a l'hivern. A mesura que avança la temporada, l'aliment esdevé més localitzat i les baldritges es concentren en les poques zones més riques. A finals de juny, pràcticament tot el contingent abandona la Mediterrània i es desplaça fins a la costa atlàntica francesa. L'hàbitat i la fenologia d'aquesta espècie coincideixen més amb la d'altres ocells marins, d'origen atlàntic, que amb els de la baldriga cendrosa o virot Calonectris diomedea. Les zones d'alimentació a la costa catalana poden tenir rellevància per a la conservació de l'espècie.Notes on Balearic Shearwater Puffinus mauretanicus phenology and habitat selection. Balearic Shearwater Puffinus mauretanicus is found in important numbers in the coast of Catalonia coinciding with Balearic Sea highest biological productivity period. Balearic Shearwater is mainly distributed on continent shelf waters, where it forages off the coast. It often forms flocks over shoals of fish mainly in autumm and winter. As the season advances, food gets scarce and the Shearwaters concentrate on the few richer areas. By the end of June, all the Balearic Shearwaters leave the Mediterranean and move to the French Atlantic coast. This species habitat and phenology are closer to the rest of Atlantic seabirds than to Cory's Shearwater Calonectris diomedea. Foraging areas on the Catalonian coast might be outstanding for Balearic Shearwater conservation

Bird population dynamics in the wintering season: the case of the mediterranean Gull Larus melanodephalus = Dinàmiques poblacionals en ocells durant la hivernada: el cas de la Gavina Capnegra Larus melanocephalus

Des de la perspectiva d’una àrea d’hivernada, el meu estudi es centra en l’ecologia de poblacions d’una espècie migratòria, a partir de la hipòtesi que els agrupaments hivernals d’ocells constitueixen veritables poblacions. Investigo la composició, estructura i dinàmiques de la població a diverses escales espacials, i el lligam entre les àrees de reproducció i hivernada connectades mitjançant les rutes migratòries. El meu model d’estudi és una població hivernant de Gavines Capnegres Larus melanocephalus formada per individus provinents de diversos orígens, una fracció dels quals han estat marcats individualment amb anelles de colors. El sistema d’estudi a la costa catalana constitueix la principal àrea d’hivernada de l’espècie a nivell mundial. Mitjançant anàlisis de captura-recaptura, estimo alts nivells de supervivència interanual local (0,81), indicatius d’una alta fidelitat a l’àrea d’hivernada que no canvia amb l’edat individual. La població s’estructura espacialment com a metapoblació, amb subpoblacions independents demogràficament. Un model probabilístic permet inferir la ruta migratòria dels ocells joves en llur primera migració; aquesta és una combinació de rutes fluvials i costaneres, cercant la mínima distància sobre terreny favorable. A escala local, l’espècie mostra alts nivells de rotació d’individus i freqüents moviments entre localitats, sense destí concret, i una baixa probabilitat de residència local (0,56). Les necessitats espacials de la població, superiors a una sola localitat, demostren la falta d’adequació amb la distribució de les àrees protegides per a espècies amb alta mobilitat. Comparant els darrers 60 anys, la distribució reproductora ha experimentat una espectacular expansió (increment areal, 750%) mentre que la distribució hivernal ha augmentat de manera moderada (25%). La població mundial ha romàs estable, indicant que el seu creixement pot estar limitat per esdeveniments de l’època hivernal. Allà on entren en contacte les poblacions reproductora en expansió i la hivernant, interactuen poc i mantenen dinàmiques independents. Aquest treball contribueix a millorar la comprensió de les dinàmiques poblacionals durant l’hivern i demostra com l’estudi de l’ecologia durant una part del cicle anual pot ajudar a comprendre el que succeeix la resta de l’any. La ‘visió des dels quarters d’hivernada’ pot aportar una informació important i complementària als estudis durant l’època reproductora.The winter period is typically associated with harsh weather conditions and reduced food availability, which may lead to increased mortality. In birds, a common strategy to avoid such risks is to migrate to more favourable grounds, but its demographic costs are largely unknown. The wintering season remains a black box in our knowledge of the life cycle of birds. From the perspective of a wintering area, I study the population ecology of a migratory species, based on the hypothesis that winter aggregations of birds constitute true populations, instead of random aggregations of individuals. I look at the population composition, structure and dynamics across several spatial scales, and the link between the wintering and breeding areas through connecting migratory routes. My study model is a population of wintering Mediterranean Gulls Larus melanocephalus made of birds from multiple origins, a significant proportion of which have been individually marked with individually-coded colour-rings in their natal or breeding colonies. The study system constitutes the species’ main winter quarters globally and is situated on the Mediterranean coast of E-NE Spain. Capture-recapture analyses reveal high estimates of apparent local interannual survival after the first year (0.81 on average), indicating a high individual winter site-fidelity that does not vary with age. This attachment to the wintering area models the distribution of individuals, shaping them into a spatially structured population with metapopulation dynamics, as each subpopulation has independent demography, determined by area-specific survival and low levels of dispersal. Using a probability model, I infer the migratory route followed by first-winter birds; the most likely path is a combination of fluvial and coastal routes, seeking minimal distance along favourable terrain. In the focus species, wintering populations are made of individuals from different sex and age classes, in one of the few documented cases of nondifferential migration. Exceptionally, the species also exhibits synheimy (the population in each distinct wintering area is made of birds from all the breeding populations), possibly as a result of its recent history. Individual choice of wintering area is made in the first migration according to a probability rule determined by distance, and is maintained through life. On a local scale, I find a very high turnover of individuals and a frequent movement, in no particular direction, among sites. The low monthly probability of local residency (0.56) contrasts with the species’ strong site-fidelity to the general wintering area. Individual turnover shows that a single site may be visited by a large proportion of the regional (43%) and global (18%) populations every season. Thus, the population home range extends over an area much larger than a single locality or a protected area, showing evidence of a mismatch between the distribution of protected areas and the spatial needs of the population. Compared with data from 60 years ago, Mediterranean Gulls have undergone a huge expansion of their breeding distribution range (750% area increase) while the wintering distribution has increased only moderately (25%). The global population size has remained stable, indicating that its growth may be limited by events taking place in the wintering season. As the breeding distribution continues to expand, where breeding and wintering populations come in contact, they interact little and follow independent dynamics. This work contributes to a better understanding of bird population dynamics in the wintering season and shows how the detailed study of a species’ ecology during one part of the annual cycle can help comprehend what happens during the rest of the year. The ‘view from the winter quarters’ can bring important and complementary information to the study of birds during the breeding period

El uso de GPS identifica nuevas rutas migratorias para las tórtolas europeas en España

Resumen del trabajo presentado al XXIV Congreso Español y VII Ibérico de Ornitología, celebrado en Cadiz del 13 al 17 de noviembre de 2019.Peer reviewe

Dinàmiques poblacionals en ocells durant la hivernada: el cas de la Gavina Capnegra Larus melanocephalus

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European Turtle-dove. Streptopelia turtur

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A new breeding population of Mediterranean Gulls Larus melanocephalus in the species' main wintering area maintains independent spatial dynamics

We studied a newly established breeding population of the range-expanding Mediterranean Gull Larus melanocephalus in eastern Spain, situated in close proximity to the species' main wintering area. By investigating the origin, population composition and wintering area of the new breeders, we found that recruitment from locally wintering birds was unlikely and that the emerging colonies were probably attracting birds from populations wintering 700–1200 km away in Portugal and southern Spain. Our findings reveal that expanding populations may follow their own dynamics, independently of other populations of the same species, and may consist of different individuals altogether.Peer Reviewe

Die Turteltaube im Übergangsbereich zwischen Wald und Ackerland: Zusammentreffen verschiedener Habitate und die Bedeutung für geeignete Managementmaßnahmen

[EN] The European Turtle Dove (turtle dove) is globally threatened after undergoing a sustained and generalised decline across its breeding range, with habitat loss suggested as the main driver. Here, we reviewed the scientific literature on habitat associations across its European breeding range, in relation to distribution, breeding numbers, nesting substrates, food and foraging habitats, to identify optimal habitat management measures. Large-scale distribution seemed related to the availability, but not dominance, of woodland landscapes; abundance was generally higher in woodland than on farmland. However, abundance in woodland increased with additional structural diversity and proximity to farmland, and abundance on farmland increased with greater availability of non-farmland features. Nesting occurred most frequently on trees (secondarily on bushes) but we found geographical differences in the type of nesting substrate, with thorny bushes being used more frequently in the north, and open canopy trees in the south. Turtle doves fed on a wide spectrum of seeds with a predominance of wild, particularly early-flowering, plants; but we could not identify a single plant species whose abundance determined turtle dove numbers. Across the distribution range, a shift from wild to cultivated seeds occurred as the season progressed. However, interventions should favour the availability and access to wild seeds. Efficient management interventions depend on the dominant habitat; overall, interventions should seek to augment landscape heterogeneity by increasing the mixing of farmland and woodland. Combined forestry and agricultural policies must provide the right conditions for ecotone species like the Turtle dove. Zusammenfassu[DE] Die Turteltaube (Streptopelia turtur) ist weltweit bedroht, seitdem sie in ihrem gesamten Brutgebiet einen anhaltenden und allgemeinen Rückgang erlebt, vermutlich in erster Linie wegen des Verlusts von Lebensraum. Um optimale Maßnahmen für ein Habitat-Management herauszufinden, werteten wir die wissenschaftliche Literatur über die Lebensräume in ihren europäischen Brutgebieten in Hinblick auf Verbreitung, Anzahl Bruten, Nistmaterial, Nahrungs- und Ernährungshabitate aus. Die großräumige Verbreitung schien mit dem Vorhandensein von Waldlandschaften zusammenzuhängen, ohne dass dies aber eine vorherrschende Bedingung war. Die Turteltauben kamen im Allgemeinen in Wäldern häufiger vor als auf landwirtschaftlich genutzten Flächen. Aber die Häufigkeit nahm mit zusätzlicher Strukturvielfalt und der Nähe zu landwirtschaftlich genutzten Flächen zu und stieg auf diesen Flächen an, wenn sie mehr Charakteristika einer geringeren landwirtschaftlichen Nutzung zeigten. Am häufigsten nisteten sie auf Bäumen (an zweiter Stelle auf Sträuchern), aber beim Nistmaterial fanden wir geographische Unterschiede, laut denen im Norden häufiger dornige Sträucher und im Süden eher offene Baumkronen genutzt wurden. Die Turteltauben ernährten sich von einer großen Auswahl an Samen, bei denen Wildpflanzen, insbesondere Frühblüher, überwogen; wir konnten aber nicht eine einzelne Pflanzenart feststellen, deren Vorkommen die Anzahl der Turteltauben bestimmte. Im gesamten Verbreitungsgebiet zeigte sich mit fortschreitender Jahreszeit eine Verschiebung von Wildsamen zu Kultursamen. Management-Maßnahmen sollten aber jedenfalls die Verfügbarkeit von und den Zugang zu Wildsamen fördern. Effiziente Maßnahmen hängen davon ab, welcher Habitattyp vorherrscht; generell sollten sie darauf abzielen, die Vielfalt der Landschaft durch einen stärkeren Mix von landwirtschaftlich genutzten Flächen und Wäldern zu erhöhen. Eine kombinierte Forst- und Agrarpolitik muss die richtigen Bedingungen für ökotone Arten wie die Turteltaube schaffen.This work was funded by the European Commission through contract ENV.D.3/SER /2019/0021 “Development of a population model and adaptive harvest mechanism for Turtle Dove (Streptopelia turtur)”.Peer reviewe