A single pelican is seen among the winged beasts (a cockatrice, an eagle, a Pegasus, a winged panther, and a gryphon) in Aslan's army. They first appeared when the Pevensies and the Beavers arrive at the Stone Table.
The pelican and the other flying creatures were also near Susan when she blew her horn to warn everyone that 2 wolves (1 of them being Maugrim) were coming, which they also saw coming. After Peter defeated Maugrim, they were ordered by Aslan to follow the other wolf and rescue Edmund. When they swooped in that night on the White Witch to attack, the pelican pecked at Ginarrbrik with its bill. Once they succeeded on their mission, they flew back to the Stone Table with Edmund.
When the White Witch came to the Stone Table the next day, the pelican and the other winged animals flapped their wings and squawked/roared/whinnied at her.
When the battle began, the flying beasts (including the pelican) began flapping their wings and squawking as the White Witch's Army approached, starting the battle. During the battle it, the eagle, and the cockatrice, swooped at the White Witch (first the eagle, then the pelican, and finally the cockatrice) before Ginarrbrik shooed them off with his whip. Upon the Witch's defeat, the pelican helped the cockatrice drive some of the ghosts and demons in her army away into a crack in a cliff.
The pelican and the other winged creatures were last seen flying to the castle for the Pevensies' coordination.