Almost more birds than leaves!

This afternoon I came home to see this neem tree (just opposite our door) full of big black birds I had never seen before:

My partner told me they had come with a herd of cattle and, indeed, some of the cows were still on our land when I drove in. What was surprising is that 1. we had never seen this bird before; and 2. we usually see the white cattle egrets with the herds.

Thanks to my very knowledgeable almost neighbour (don't be too litteral at that: he lives about 30km from here), I was able to put a name on this bird: it's a Piapiac / Ptilostomus afer / Piapiac africain.