On 31 October 2011 a 2-hour count (08:30 to 10:30) was made of southward passerine migration through Sierra de Gata. The counting site was the pass called Puerto Viejo de Robledillo de Gata (Cáceres) on the border with Salamanca Province. Most birds were flying in single-species flocks, though there were also some mixed-species flocks, especially multi-finch flocks and Chaffinches with Meadow Pipits. The total count came out as 161 flocks and 757 birds; 13 different species were identified. The commonest were Chaffinch (63% of the total), Meadow Pipit (9%) and Goldfinch (7%). On the days before and after the count there was also visible migration of Linnets, Crag Martins and Corn Buntings. On other dates intense migration of Bee-eater and Swift was observed. It should be stressed here that our lookout point was only one shoulder of land among many in Sierra de Gata, ostensibly without any characteristic that might favour passage. From this pass, and also from the neighbouring pass of La Ventanera just to the east, the passage is funnelled through the valley of River Árrago towards the Cáceres plains.
At the moment an Environmental Impact Statement is pending on the 60-generator windfarm that would be set up precisely on the Salamanca side of this part of Sierra de Gata. The mockup below shows how windpower generator AR17 would be sited on the lookout point used in this count, and the AP1 on the shoulder of land known as Collado de La Ventanera. The compulsory Environment Impact Study before the actual ruling included an ornithological study. This study omitted this important passage point and even downplayed the importance of Sierra de Gata as a whole for bird migration. The simple study we conducted has shown that the passage of certain species tends to be concentrated in a few days at specific times. They are therefore species that might well be underestimated if the counts are not made at the right point and time. This sizeable passage is yet another reason for conserving these exceptional though overlooked sierras in western Iberia.
