While going through my Flag Stamp collections, I found there are a number of Flag stamps which besides other symbols conspicuously have Dove - the International Symbol of Peace. As you know, the terms "dove" and "pigeon" are used somewhat as synonyms. In ornithological parlance, there is a tendency for "dove" to be used for smaller species and "pigeon" for larger ones, but this is in no way always applied. This bird family occurs worldwide and the whole world is their home.
Interestingly, most of the ‘Flag and Dove stamp' have more than one flag and have been issued to commemorate various International Peace Movements, Signing of Treaty, expressing solidarity with other nations on matter of common interests/causes – political, social and/or cultural, and many other myriad subjects.
Amongst many Peace Symbols used in various cultures and contexts, one of the most ancient being Dove. The symbols of the Dove and Olive branch as Peace Symbol was used by early Christians and was later adopted as a secular symbol.
Wall painting from the early Christian Catacombs of Marcellinus and Peter in Rome, showing Noah, in the Orante attitude of prayer, the dove and an olive branch.(Wikipedia) .