Rosy Bee-eaters return to the Ogooué's low-water sandbanks

Two Rosy Bee-eaters (Merops malimbicus) were seen on 7 August at Lambaréné, along the Ogooué near the Schweitzer hospital.¹ Once in view the bird is hard to confuse with anything else on the river: slate-grey above, deep rose-pink from throat to belly, a clean white stripe running back beneath a red eye, and a squared tail without the long central streamers most bee-eaters carry. It is a little bigger than a starling and seldom alone; a rolling, chattering call usually gives a flock away before the pink does.

The bird's tie to the Ogooué is where it nests. Rosy Bee-eaters dig their nest tunnels into flat, bare river sand, and they do it together, in colonies that on the big rivers of Central and West Africa have run to thousands of pairs and in the largest cases tens of thousands, each burrow a hand's width from the next. A colony on that scale can only exist on a sandbank, and a sandbank only exists when the river is low. Early August at Lambaréné is the heart of Gabon's long dry season, which runs roughly June through September, when the Ogooué drops to its lowest stage of the year and its bars and islands come out of the water. That is the window. The birds arrive, excavate, lay and raise young while the sand is dry and firm, and the colony has to be finished before the October rains bring the river back over it.

Between breeding seasons the species does not sit still. It moves in nomadic flocks across the forest-savanna mosaic, hawking insects on the wing, and two things pull it in particular: the leading edge of a grass fire, where the heat flushes insects into the air, and the clouds of winged termites and ants that pour out of the ground after rain. Those emergences are rain-triggered, so as the dry season breaks the flocks have something to follow.

A pair on the riverbank at Lambaréné in the first week of August is the bird exactly where and when it belongs. Anyone on the Ogooué in August or September who finds a low, bare sandbar pocked with holes, with grey-and-pink birds streaming in and out over the water, has found the reason this species lives here.