Cuckoo head shades
I've seen Oriental Cuckoo (singing) with head clearly paler than mantle/wings.
Indeed, came to believe this was a useful identification feature - till I saw one on migration (Happy Island) - saw head clearly paler than dark looking wings/mantle, thought "Oriental": and it started singing. (Oops!)
"oriental cuckoo" shot from Taiwan showing pale head:
http://flickr.com/groups/taiwanbird/discuss/72057594094686938/