In areas where both the Great White Pelican and the Dalmatian Pelican occur (such as Romania), they are sometimes difficult to distinguish.
However, the Dalmatian Pelican has a light iris, whereas the Great White Pelican has a dark iris.
Furthermore, the throat pouch of the Dalmatian Pelican is orange-red; in the Great White Pelican, it is yellow.

First 4 photos: Mila 23 area, Danube Delta, Romania, 23 May 2018
Last photo: Jurilovca area, Tulcea County, Romania, 21 May 2018