Another two black & white birds I've spotted in Nigeria.
1. I don't think the image is a African Pied wagtail as beak is too thick (plus it wasn't wagging its tail much either). I've checked Wikipedia to no success.
2. The other black & white bird, similar size to that in the image but spotted in a tree. Similar patterns as the one photographed, but with the following. White breast, black beak, most noteable was a prominent red patch around the eyes.