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Oversea migration of white storks through the water barriers of the straits of Gibraltar

Soaring landbirds typically exploit atmospheric uplift as they fly overland, displaying a highly effective energy-saving locomotion. However, large water bodies lack thermal updrafts, potentially becoming ecological barriers that hamper migration. The effects of a sea surface on the migratory performance of GPS-tagged white storks (Ciconia ciconia) were assessed before, during and after they crossed the straits of Gibraltar. Oversea movements involved only flapping and gliding and were faster, traversed in straighter, descending trajectories and resulted in higher movement-related energy expenditure levels than overland, supporting the water barrier hypothesis. Overland movements at both sides of the sea straits resulted in tortuous routes and ascending trajectories with pre-crossing flights showing higher elevations and more tortuous routes than post-crossing, thus supporting the barrier negotiation hypothesis. Individual positions at both ends of the sea narrow were predicted by zonal winds and storks´ location at entry in the European hinterland, and birds did not show compensational movements overland in anticipation to subsequent wind displacements oversea. The length of the water narrow at departure shore, the elevation therein and the winds on route affected major components of sea crossing performance (such as distances and times overwater, minimum elevations, climb angles, speeds and energy expenditure), supporting the departure position and oversea winds hypotheses. In summary, this study provides a prime example at high temporal resolution of how birds adjust their behavior and physiology as they interact with the changing conditions of the travelling medium, reallocating resources and modifying their movement to overcome an ecological barrier. informacion[at]ebd.csic.es: Blas et al (2020) Overland and oversea migration of white storks through the water barriers of the straits of Gibraltar. Scientific Reports 10: 20760. DOI 10.1038/s41598-020-77273-x. See Spanish press release


www.nature.com/articles/s41598-020-77273-x
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Angiosperm seeds lacking external flesh can be adapted for endozoochory

Angiosperm seeds lacking external flesh can be adapted for endozoochory

It is often assumed that only plants with a fleshy fruit disperse inside vertebrate guts, i.e. by "endozoochory". However, only 8% of European angiosperms have a fleshy fruit, and endozoochory of other plants by herbivorous or granivorous birds and mammals is widespread in nature. Many terrestrial and aquatic plants disperse via endozoochory by migratory waterbirds, providing long-dispersal dispersal. But how do they survive gut passage? Is the mechanical resistance to digestion different to that recorded in fleshy-fruited plants? Using SEM and 11 plants we compared seed morphology before and after gut passage through mallards. Diverse seed and dry fruit architecture provided multiple mechanisms to resist digestion and so enable seed survival. There are no fundamental differences in the way that these seeds, or those from fleshy-fruited plants, survive gut passage. Both plant types are pre-adapted for endozoochory and for seed dispersal mutualisms. informacion[at]ebd.csic.es: Costea et al (2019) The Effect of Gut Passage by Waterbirds on the Seed Coat and Pericarp of Diaspores Lacking "External Flesh": Evidence for Widespread Adaptation to Endozoochory in Angiosperms. PLoS ONE 14(12): e0226551


https://doi.org/10.1371/journal.pone.0226551