Pallid Swifts are generally quite common in Greece, especially in the coastal areas. However, their identification is always difficult, since most of the times the sun is not helping at all. The safest way is finding a small pool or river that attracts all swifts for drinking and getting a really close look when they approach.
Pallid Swifts tend to stay longer in their breeding grounds, usually until late September, while Common Swifts leave earlier.