The mistery of the route to the Cantabric Sea solved!

Tracking data offered a first breakthrough to solve the mystery of the route to the Cantabric Sea.   
Yellow-legged gulls from the Balearic islands have been regularly seen in the Cantabric coast, but the route to Northern Spain was a mystery. Do they fly around the Iberian peninsula or throught the Ebro valley ? Do they use the Ebro river as a landmark? Do they reach the Cantabric sea from France? 
Last year preliminary data provided a first piece of the puzzle when a gull moved North following the Ebro river to Zaragoza. However the radio failed at the end of the summer and the route to the Cantabric sea along the Ebro river was not proved. This summer tracking data deliver the solution to the mystery, showing what is likely to be the main route to the Cantabric Sea: the Ebro valley. Interestingly, the route seems to pass north of the river and through the Basque Mountains at Estella. To be continued....

Yellow Legged Gulls: new tracks !

A Yellow Legged gull marked as a breeder in Dragonera Island (Balearic archipelago) moved North to Barcelona. It continued the journey to Narbonne. Will it move up the Canal Du Midi or move to Camargue ? Place your bet.

To be continued....

Summering in Eastern Spain

The three Yellow Legged Gulls equipped with GPS-GSM in Mallorca at the beginning of this summer decided to spend the summer in different places. As many tourists, however, they chose to spend the summer in North-Eastern Spain. One (green cyrcle) moved up to Zaragoza, a second one stayed in Mallorca (blue cyrcle) and a third spent the summer near Barcelona (red cyrcle). 

Soon will be time to decide where to spend the winter ..?! 

First long tracks from Dragonera

The GSM/GPS devices are sending interesting information on bird movements. Marked gulls seem to have moved their core area northward, between the delta of the river Llobregat and the landfill, north of Barcelona city.

New Publication !

Sergio, F., Taferna A., De Stephanis, R., López Jiménez, L., Blas, J., Tavecchia, G., Preatoni, D., and Hiraldo, F., 2014: 'Individual improvements and selective mortality shape lifelong migratory performance'. Nature. doi:10.1038/nature13696

Billions of organisms, from bacteria to humans, migrate each year and research on their migration biology is expanding rapidly through ever more sophisticated remote sensing technologies. However, little is known about how migratory performance develops through life for any organism. To date, age variation has been almost systematically simplified into . These comparisons have regularly highlighted better migratory performance by adults compared with juveniles, but it is unknown whether such variation is gradual or abrupt and whether it is driven by improvements within the individual, by selective mortality of poor performers, or both.

Here we exploit the opportunity offered by long-term monitoring of individuals through Global Positioning System (GPS) satellite tracking to combine within-individual and cross-sectional data on 364 migration episodes from 92 individuals of a raptorial bird, aged 1–27 years old. We show that the development of migratory behaviour follows a consistent trajectory, more gradual and prolonged than previously appreciated, and that this is promoted by both individual improvements and selective mortality, mainly operating in early life and during the pre-breeding migration. Individuals of different age used different travelling tactics and varied in their ability to exploit tailwinds or to cope with wind drift. All individuals seemed aligned along a race with their contemporary peers, whose outcome was largely determined by the ability to depart early, affecting their subsequent recruitment, reproduction and survival. Understanding how climate change and human action can affect the migration of younger animals may be the key to managing and forecasting the declines of many threatened migrants.

See also at IMEDEA (CSIC-UIB) and IMEDEA Divulga here