TANDEM FLIGHT BY GRIFFON VULTURES (GYPS-FULVUS)

Tandem flight is a formation that momentarily reunites two vultures fl ying one above the other at a very short distance. Our study adds the following points to our current knowledge of the subject: (i) the onse t of tandem flight is always initiated by only one of the two birds (b ird A) that positions itself above the other (tandem A/B), whereas its disruption can be initiated by either of the birds; (ii) the position of the wings in bird A makes its flight very unstable, which ensures maneuverability in dealing with the turbulence caused by bird B. The l atter has a more peaceful flight, apparently independent of bird A; (i ii) these tandem flights have a mean duration of about 10 s and always follow a straight course; (iv) most frequently, tandem flights reunit e birds that are mating partners, and the female usually occupies the top position. We hypothesize that this type of flight may enhance the aerodynamic performance of the united birds, further tightening the bo nds between pairs. This association seems to serve as a model to other vultures, which sometimes join the paired birds. The piling up that r esults often gives rise to aggressive behaviours that reflect the riva lry between all these birds.