This ambient sound effect was recorded with high quality sound equipment and comes from a sound library called Cormorants which is pack of 32 audio files with a total length of 119 minutes. It's a library recorded in the colony of the Cormorant birds. Recordings in this library features sound of more than 1000 birds singing at the same time, including recording from nests of the nestlings and seagulls. You can use this sound for free, and if you need a whole package of ambients you can support my work and get it for 40$ here: http://soundholder.com/product/sound-library-cormorants/
Also here's a 10% discount code for all freesound users, just type : freesound in discount window.