Common birds: Red-billed Quelea, commonest bird in the world?

1000s of quelea at a dam on Manyara Ranch

I've been struggling to think of the next common bird to do something interesting with, until the obvious solution came to me, possibly the world's most abundant bird, the red-billed quelea.

So, first the identification. The most obvious thing about red-billed queleas are, as the name suggests, a large red beak! Apart from that feature, females and non-breeding males are rather nondescript, small sparrow-like birds. Breeding males are rather brighter, with the red bill surrounded by a black face and variable amounts of orange on the top of the head and breast, with otherwise sparrow-like brown streaks on the back and wings. Perhaps the most useful identification feature though is the fact that you almost never see just one, but flocks of tens, hundreds or thousands of busy quelea all searching for grass seeds or drinking at waterholes.