The maximum width of the strait is 14km (c. 9 miles) and that makes this area especially important for soaring birds (storks, vultures, eagles, etc.), which, during autumn migration, concentrate in hundreds of thousands waiting for suitable winds to cross the Strait.   The Regional Government of Andalucía (Consejería de Medio Ambiente, Junta de Andalucía) is funding, from 1997 onwards, the monitoring of the autumn migration of soaring birds, the first phase of which is a long term scheme at the Strait of Gibraltar (Programa Migres).  Coordination of the field work is done by the Spanish partner of BirdLife International, SEO/BirdLife (Sociedad Española de Ornitología). EGMASA and Fundación Migres also provide support for the project. During four months (mid July-mid October) of each year, several observatories are placed along the Spanish migration front of the Strait of Gibraltar and volunteers cover them, together with the specialists responsible for the project. 

Volunteers carry out bird counts from predetermined watch-points, with a flexible timetable (but no less than 11 hours daily) depending on the migration conditions.  Every day, once the observation work is over, all the volunteers meet with field work co-ordinators to check the data obtained and resolve any questions regarding bird behaviour and counts.  

Click the images to watch the graph for each species in the 2005 season