Get robbed ... eat better?
This is Sandra Tsing Loh with the Loh Down on Science.
The African drongo habitually steals food from another bird species, the pied babbler. The drongo perches above the ground-foraging babblers and waits. When ready to rob, it whistles "predator!" in bird language. The babblers scatter, fumbling their findings, and the clever klepto swoops in and nabs the easy pickins.
Turns out, though, it's the babblers that make out like bandits. Andrew Radford, from the University of Bristol, noticed that drongos mutter to themselves, producing so-called “twanks” every few seconds. Every time babblers heard these sounds they foraged harder. They moved out from under bushes, expanded their hunting grounds, and ultimately ate twice as much prey as normal.
Why? Because drongos also produce true predator-warning calls, to keep victims guessing. So when a drongo's near, but not sounding an alarm, its continuous muttering is an all-clear signal. The babblers keep their heads down and gobble up everything in sight. Could call it ... twitter feeding. This more than offsets any stolen snacks.
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