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The Aquatic Warbler (Acrocephalus paludicola) in the Djoudj National Park area - Aspects of its wintering ecology
Get PDFThe globally threatened Aquatic Warbler (Acrocephalus paludicola) is the rarest migratory songbird in Europe. Before the population declined dramatically after 1960, the Aquatic Warbler was a common species in European mires and river flood¬plains. Today, the global population is estimated to count 27 600 individuals, of which approx. 90 % are concentrated in only three countries during the breeding season: Belarus, Poland and Ukraine. Despite numerous conservation efforts mainly under¬taken in European countries, the population decline has not been stopped. Although the Aquatic Warbler is considered a “European” bird species because of the location of its breeding grounds, it spends up to six months on migration and on the wintering grounds on the African continent. A comprehensive species conservation strategy must therefore include the preservation of African resting and wintering grounds. This study analyses the ecol¬ogy of Aquatic Warbler in its wintering grounds using the example of the Djoudj National Park area in north-western Senegal. The study aims, first, to close knowledge gaps regarding the behaviour and the habitat requirements of Aquatic Warblers during their stay on the wintering grounds to provide a scientific base for long-term species conservation management; second, to assess the importance of the wintering site in the Djoudj area is in a global perspec¬tive; and third, to identify threats to the Djoudj area as a suitable Aquatic Warbler habitat. In a fourth step, science-based management recommendations are formu¬lated to support the ongoing practical conservation work of the Djoudj National Park administration with regard to the Aquatic Warbler. The main outcomes of the study are the following: (I) We confirmed the presence of Aquatic Warblers in the Djoudj area between mid-December and the end of March. (II) The connection between the wintering ground “Djoudj National Park area” and the breeding ground “Biebrza valley” (eastern Poland) was confirmed by the resighting of a ringed Aquatic Warbler individual. (III) The remiges moult of the species was observed under natural conditions for the first time. We confirmed that the Aquatic Warbler undergoes a complete moult on its wintering grounds, following the typical sequence of passerine moult. (IV) Aquatic Warblers occur in shallowly inundated vegetation with dominant stands of Oryza longistaminata, Eleocharis mutata, Scirpus maritimus, Scirpus litto¬ralis and Sporobulus robustus interspersed with small (1–2 m²) areas of open water. The afore mentioned herbaceous species form a homogenous wetland vegetation of approximately 0.6–1.5 m height, with a coverage of 80 % to 100 %. Wild rice (Oryza longistaminata) may provide the most suitable habitat conditions as suggested by the very high density of Aquatic Warblers at sites dominated by this species. Preferential habitat may include a few solitary trees, but open woodland or scrublands are unsuit-able for Aquatic Warbler. Pure stands of cattail (Typha australis) are avoided. The water level in the habitat areas varies between 0 (humid soil) and 40 cm above the ground. Constant inundation seems to be essential, as Aquatic Warblers were never encountered in dry parts of the study area. All known Aquatic Warbler habitats in the study area are influenced by brackish or salty water. (V) During winter Aquatic Warblers use a home range of 3.9 ha (± 1.9) in aver¬age, which is shared with other individuals and species. No territorial behaviour was observed in the winter quarters. (VI) The vegetation and land cover map prepared distinguishes six classes of her¬baceous vegetation and five general land cover classes. (VII) There are 4 729 ha of potential Aquatic Warbler habitat within the study area. (VIII) We estimate the density of the Aquatic Warbler population in the study area to range between 0 and 2.26 individuals per hectare with a total population size of 776 individuals, or 260–4 057 individuals in a 95 % credibility interval. Hence we conclude that 1.1–3.8 % (0.37–19.8 % within the 95 % credibility interval) of the global Aquatic Warbler wintering population are found in the Djoudj area. (VIII) The Aquatic Warbler habitats in the Djoudj area are affected by the inun¬dation regime, water circulation, changes in salinity, grazing, the spread of cattail (Typha australis), the encrustation of vegetation, the protection status of passerine migrator habitats and the expansion of rice cultivation a. Our management proposals for the preservation of existing and the development of new Aquatic Warbler habitats were formulated and incorporated into the Management Plan of the Djoudj National Park 2014–2018.Der weltweit bedrohte Seggenrohrsänger (Acrocephalus paludicola) ist der seltenste ziehende Singvogel Europas. Vor dem Einbrechen der Population nach 1960 war der Seggenrohrsänger eine häufige Art in europäischen Niedermooren. Heute wird die Gesamtpopulation auf 27 600 Individuen geschätzt, wovon circa 90 % während der Brutzeit in dem Länderdreieck Weißrussland, Polen und Ukraine konzentriert sind. Trotz zahlreicher Schutzbemühungen in den europäischen Brut- und Rastgebieten konnte der kontinuierliche Populationsrückgang der Art bisher nicht gestoppt werden. Obwohl der Seggenrohrsänger auf Grund der geographischen Lage seiner Brutgebiete als eine "europäische" Vogelart gilt, verbringt er während des Zuges und in den Winterquartieren bis zu sechs Monate des Jahres auf dem afrikanischen Kontinent. Für einen umfassenden Schutz der Art ist es daher ebenso wichtig, die afrikanischen Rast- und Überwinterungsgebiete zu erhalten. Die vorliegende Arbeit soll Wissenslücken über das Verhalten und die Lebensraumansprüche des Seggenrohrsängers während seines Aufenthalts in den Überwinterungsgebieten schließen, um eine wissenschaftliche Grundlage für seinen langfristigen Erhalt zu schaffen. Des Weiteren soll die globale Bedeutung des Djoudj Nationalparks als Überwinterungsgebiet der Art ermittelt sowie die eventuelle Bedrohung seiner Habitate abgeschätzt werden. Ausgehend von den Ergebnissen werden Managementempfehlungen für die laufende praktische Naturschutzarbeit im Djoudj-Nationalpark vor allem hinsichtlich des Seggenrohrsänger formuliert. Die wichtigsten Ergebnisse der Arbeit sind die folgenden: (I) Die Anwesenheit von Seggenrohrsängern im Djoudj-Gebiet zwischen Mitte Dezember und Ende März wurde bestätigt. (II) Die Beobachtung eines im Djoudj-Gebiet beringten Seggenrohrsängers im Brutgebiet „Biebrza“ in Ostpolen bestätigte die Verbindung zwischen dem jeweiligen Brut- und Überwinterungsgebiet. (III) Die Großgefiedermauser des Seggenrohrsängers wurde zum ersten Mal unter natürlichen Bedingungen beobachtet. Es konnte bestätigt werden, dass der Seggenrohrsänger eine vollständige Mauser im Anschluss an den Herbstzug im Winterquartier durchführt; diese folgt der typischen Abfolge der Großgefiedermauser von Singvögeln. (IV) Seggenrohrsänger treten in flach überfluteten Habitaten mit dominanten Beständen von Oryza longistaminata, Elecharis mutata, Scirpus maritimus, Scirpus littoralis und Sporobulus robustus auf, die mit kleinen (1–2 m²) offenen Wassersflächen durchsetzt sind. Die krautigen Arten bilden eine homogene Feuchtgebietsvegetation von ca. 0,6–1,5 m Höhe mit einer optimalen Deckung von 80 % bis 100 %. Die hohe Dichte von Seggenrohrsängern in Habitaten mit dominanten Beständen von Wildem Reis (Oryza longistaminata) zeigt, dass diese Pflanzenart bevorzugt wird und sehr geeignete Lebensbedingungen gewährt. Solitärbäume treten in geeigneten Habitaten auf, jedoch sind Offenwälder oder Gebüsche ungeeignet für den Seggenrohrsänger. Reinbestände von Rohrkolben (Typha australis) werden gemieden. Der Wasserstand in den Habitaten variiert zwischen 0 (feuchter Boden) und 40 cm über der Geländeoberfläche. Eine dauerhafte Überflutung der Flächen ist eine Voraussetzung für die Eignung der Habitate, da Seggenrohrsänger nie in ausgetrockneten Teilen des Untersuchungsgebietes angetroffen wurden. Alle bekannten Lebensräume des Seggenrohrsängers im Untersuchungsgebiet sind durch Brack- oder Salzwasser beeinflusst. (V) Im Überwinterungsgebiet nutzt der Seggenrohrsänger Home Ranges von durchschnittlich 3.9 ha (± 1.9) Größe, welche mit anderen Individuen und Arten geteilt werden. Während des Winters zeigt die Art kein revierverteidigendes Verhalten. (VI) Die erstellte Vegetations- und Landnutzungskarte unterscheidet sechs Klassen von krautiger Vegetation und fünf allgemeine Landnutzungsklassen. (VII) Es konnten 4 729 ha geeignetes Seggenrohrsängerhabitat im Untersuchungsgebiet festgestellt werden. (VIII) Die Dichte der Seggenrohrsänger im Untersuchungsgebiet betrug 0 bis 2,26 Individuen pro Hektar bei einer Populationsgröße von 776 Individuen bzw. 260–4 057 Individuen in einem 95 % Glaubwürdigkeitsintervall (credibility interval). Daraus läßt sich ableiten, dass 1,1 bis 3,8 % (0,37–19,8 % innerhalb des 95 %-Glaubwürdigkeitsintervalls) der globalen Population im Gebiet des Djoudj-Nationalparks überwintern. (VIII) Das Überschwemmungsregime, die Wasserzirkulation im Überschwemmungsgebiet, Änderungen der Salinität, Beweidung, Ausbreitung von Rohrkolben, das Verkrusten der Vegetation, der Schutzstatus einzelner Lebensräume und die Ausweitung des Reisanbau im Untersuchungsgebiet beeinflussen die Lebensräume des Seggenrohrsängers. Managementvorschläge für den Erhalt bestehender und die Entwicklung neuer Seggenrohrsängerhabitate wurden formuliert und in den Managementplan des Djoudj-Nationalparks für den Zeitraum 2014–2018 integriert
Home range and habitat use by aquatic warblers acrocephalus paludicola on their wintering grounds in Northwestern Senegal
No full textThe Aquatic Warbler Acrocephalus paludicola was once a common breeding bird in mesotrophic fen mires all over Central and Western Europe. In the last century large parts of its habitat have been destroyed by wetland drainage and agricultural intensification. Besides protecting the remaining breeding habitats, it is of great importance to preserve suitable migration stopover habitats and wintering grounds to avert the extinction of the species.
We determined home-range size and the use of vegetation associations of Aquatic Warblers on the wintering grounds in a flooded plain north of the Djoudj National Park in Senegal. Individual birds (11) were caught in mist nets and equipped with radio transmitters. Locations were assessed by radiotelemetry and a compositional analysis was conducted to determine which vegetation types were preferred within home ranges.
Similar to their behaviour on the breeding grounds, the Aquatic Warblers showed no territorial behaviour in their winter quarters. They used home ranges that averaged 4 ha in size, which they shared with conspecifics and other warblers. The home ranges overlapped 54% on average, with a maximum of 90% in an area used by four individuals. The vegetation structure of the wintering habitat is similar to breeding grounds and stopover sites of the species. Preferential vegetation had 80% to 100% cover and consisted of 60 to 90 cm high stands of Oryza longistaminata, Scirpus maritimus or Eleocharis mutata. Most birds stayed more often near the edge of open water, probably for foraging. A constant inundation seems essential, because Aquatic Warblers never occurred in desiccated parts of the study site
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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