This is a sound effect that can be found on the Freesound website. It was uploaded to the site on June 5, 2010 by user "justkiddink".
Not only can seagulls be heard as implied, but a crow can also be heard.
Sound Effect Description
Seagulls flying 15-30 meters directly above me.Hard to count how many but using the local fishermans formula of 10 seagulls for each bird-dropping left on jacket gives 100 birds.