The three bills

Mana Pools has several oxbow lagoons that occupy the old course the Zambezi carved in the valley a very long time ago. There are four larger pools that give the name Mana (four) in the Shona language. Of the four I can name only name two: Long and Chini. I am still trying to name the others!

Long pool and hippos.

Long pool and hippos.

Long Pool is perhaps the better known of the four. It is a sizeable body of water where several animals are resident, including a large number of hippos and crocodiles, some of the latter really humongous, often spotted basking on its edge. With the exception of a grey heron that enjoys “hippo surfing”, most water birds are found in the shallows. The species and numbers present clearly depend on the season but Goliath and Grey herons, Hammerkop, and Stilts are normally present.

Obviously the bills of the birds are suited to different feeding strategies. On this occasion we found three different ones that actually give the names to the birds: the African Open-billed and Yellow-billed storks and the African spoonbill. They were sharing the same feeding ground at Long pool so we stopped and watched.

The three bills.

The three bills.

The Spoonbill, the less common of the three, waded through shallow water sweeping from side-to-side with bill open and inside the water. Occasionally it dashed around, chasing fish(?) like an egret does. When something edible was found, the bill snapped shut and the victim was swallowed.

A rare pause in the wadding.

A rare pause in the wadding.

The Yellow-billed stork fed walking slowly with half-submerged and slightly open bill. As the later is very sensitive to contact with potential prey, it also snapped closed when that happened.

Typical African yellow billed stork feeding pose.

Typical African yellow billed stork feeding pose.

While the two bills from the birds above are odd, they make sense from the feeding technique point of view.

It caught something small and muddy!

It caught something small and muddy!

Feeding with your bill open and shut it when catching prey is one thing, feeding with your bill open and keep it open when shutting it is another! “A priori” it seems to be pushing nature’s ingenuity to extremes! However, the African open-bill stork was also wading and catching prey, though a bit muddy!

Further reading indicated that its bill is a highly specialized tool to perform an almost surgical intervention on its main prey: snails. It has several uses, depending on the size and type of snail: it either cracks it (large ones), removes its body by shaking its head or it cuts the snail’s columellar muscle[1] with its sharp tip.

Feeding together.

Feeding together.

Although the three birds feeding paths often crisscrossed, they were respectful of each other as if benefiting from each other’s presence. The say “when the river is dirty the fisherman benefits” is likely to apply here!

Mana Pools, Zimbabwe, September 2015.

[1] The columellar (shell) muscles of gastropods join the foot and other parts of the body with the shell. (Basically, keeping the animal together!)

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