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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] 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
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Global geographic patterns in the colours and sizes of animal dispersed fruits

Global geographic patterns in the colours and sizes of animal dispersed fruits

Fruit colours attract animal seed dispersers, yet the causes of fruit colour diversity remain controversial. The lack of knowledge of large?scale spatial patterns in fruit colours has limited our ability to formulate and test alternative hypotheses to explain fruit colour, fruit size and fruit colour diversity. Spatial (especially latitudinal) variation in fruit colour, colour diversity and length has been described, and tested for correlations between fruit colour, length and plant habit, assembling a database of fruit traits for 13,178 fleshy fruited plant species spanning 136 sites around the world. Fruit length (both mean and variance) increases towards the tropics. Tropical communities tend to have diverse fruit colours, including many mammal?associated fruit colours (green, orange, brown and yellow), while high latitude communities contain a higher percentage of red?fruited species. The correlation between colour and size is strong, and some latitudinal patterns may be partly driven by changes in fruit size. Fruits may be larger in the tropics than at high latitudes because dispersers in the tropics tend to be larger, but there are other possible explanations. The Northern and Southern Hemispheres differ in the diversity of fruit colours across latitude, with the Southern Hemisphere having higher colour diversity, similar to the tropics. Differences in geography and in the history of plant lineages in the Southern versus the Northern Hemisphere may help to explain some biogeographic patterns, but alternative hypotheses related to fruit defence, development and metabolic costs are plausible. informacion[at] Sinnott-Armstrong et al (2018) Global geographic patterns in the colours and sizes of animal-dispersed fruits. Glob. Ecol. Biogeography