TÉLÉCHARGER NO FLOCKING GRATUITEMENT

StructId : Hide details Abstract : Murmuration, i. It is now well accepted that this collective behavior emerges from individual ones and that no global control is involved. In other words, every starling has an equivalent status in the flock and there is no leader deciding how the murmuration evolves. Considering this phenomenon , Reynolds' individual-based rules have been investigated and implemented a number of times to create compelling computer-animated models of the aerial movement of swarm-like flocks of starlings. Still, it turns out that implementing Reynolds' model is not sufficient per se in the sense that all murmuration simulations use tricks to achieve a convincing animation of this phenomenon. Especially, virtual leaders or points of interest are used to orientate the starlings, which somehow contradicts the no-global-control perspective, and thus suggests that murmu-ration dynamics is not yet fully grasped.

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Search Menu Abstract Mixed-species flocks are ubiquitous in forest bird communities, yet the extent to which positive facilitative or negative competitive interactions structure these assemblages has been a subject of debate. Here, we describe the fine-scale foraging ecology and use network analysis to quantify mixed-species flocking interactions of an insectivorous bird community in hardwood forests of north-central Florida.

Our goal was to determine if similarly foraging species are more facilitation hypothesis or less competition hypothesis likely to associate in flocks, and if foraging ecology can explain intraspecific abundance patterns within flocks. We quantified attack maneuvers, foraging substrate, and foraging microhabitat of all 17 common insectivorous species in these forests and characterized the composition of 92 flocks encountered. Our results supported both hypothesized mechanisms structuring flock composition.

Species had distinct, well-defined foraging niches during the nonbreeding season, but foraging niche overlap among flocking species was greater than expected by chance. Consistent with the facilitation hypothesis, we found that similarly foraging species were significantly more likely to associate in flocks, a result driven by lower association strengths in large-bodied woodpeckers.

We found no evidence of assortment by foraging behavior, however, likely because foraging behavior and substrate use showed strong niche partitioning at the fine scale within our community.

Intraspecific abundance patterns were significantly linked to foraging substrate use, with live leaf use correlated with high within-flock abundance and relative abundance at study sites.

Species that specialized on comparatively less abundant substrates tree trunks, epiphytes, dead leaves joined flocks as singletons, showed lower relative abundance, and may exhibit nonbreeding territoriality. Our results highlight the importance of foraging substrate use and mixed-species flocks in structuring the nonbreeding ecology of migratory birds. Resumen Las bandadas de especies mixtas son muy conspicuas en las comunidades de aves de bosque; sin embargo, hasta qué punto las interacciones positivas facilitación o negativas competencia estructuran estos ensambles ha sido tema de debate.

Nuestros resultados apoyan los dos mecanismos que hipotetizamos que estructuran la composición de las bandadas. Las especies tuvieron nichos de forrajeo bien definidos durante la estación no reproductiva, pero la superposición del nicho de forrajeo entre las especies de las bandadas fue mayor que lo esperado por azar.

No encontramos evidencia de una separación por comportamiento de forrajeo, probablemente debido a que el comportamiento de forrajeo y el uso del substrato mostraron una fuerte partición del nicho a escala fina dentro de nuestra comunidad. Los patrones de abundancia intraespecífica estuvieron significativamente vinculados al uso del sustrato de forrajeo, con el uso de hojas vivas correlacionado con la alta abundancia dentro de la bandada y la abundancia relativa en los sitios de estudio.

Nuestros resultados destacan la importancia del uso del substrato de forrajeo y de las bandadas de especies mixtas en estructurar la ecología no reproductiva de las aves migratorias. All rights reserved. For permissions, e-mail: journals.

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