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Tiny Birds Play a Tit-for-Tat Game

By Ross Pomeroy

We humans are well versed with the concept of reciprocity. You help me; I help you. But, if you don't help me, I may not be so inclined to lend assistance when you're in need. Well, it appears a chirpy little passerine bird may play a similar same tit-for-tat game.

European pied flycatchers are commonly found in Europe and western Asia. They mate in pairs, and one of the parents' primary concerns is protecting their brood from predators, usually owls.

To examine whether or not flycatchers employed reciprocity for predator defense, a team of biologists set up numerous pairs of nest boxes in a forest in southeastern Latvia. Some of the pairs were installed near to each other, between 20 and 24 meters away (close). Other pairs were separated by longer distances of 69 to 84 meters (far).

First, in two control experiments, the researchers sought to determine if mating pairs of flycatchers would help their neighbors if they came under attack from an owl. In nest box pairs, when a stuffed owl was presented at nest box #1, the flycatchers located in nest box #2 would come to their aid to fight off the owl. In turn, when a stuffed owl was presented at nest box #2 one hour later, the neighbor flycatchers from nest box #1 would come to help out. This occurred in all 12 experiments that were conducted for "close pairs," as well as in all 12 experiments for "far" pairs.

Next, the researchers sought to determine what would happen if neighbor birds weren't so helpful. A stuffed owl was presented at nest box #1, but birds from nest box #2 were kept in captivity. Alarm calls were played from box #2, within earshot of their neighbors. Thus, nest box #1 birds in phase one had to fend off the fake owl on their own, presumably knowing that their neighbors didn't show up to help out.

When the owl was presented an hour later at nest box #2, "close" neighbors aided the no-shows from nest box #2 in 12 of 12 experiments, while only 2 out of 14 "distant" neighbors aided the no-shows. Upon hearing their neighbors' alarm calls, the other 12 flycatcher pairs from the "distant" experimental subgroup interrupted their feeding and gave alarm calls of their own, yet they didn't come to their neighbors' aid.

In light of the results, it appears that flycatchers take into account distance when deciding whether or not to help their neighbors fend off predators. But more intriguingly, flycatchers will come to the aid of neighbors that previously helped them, regardless of distance, and will spurn neighbors that didn't.

The study was published Nov. 12th in Scientific Reports.

Source: Tatjana Krama, Jolanta Vrublevska, Todd M. Freeberg, Cecilia Kullberg, Markus J. Rantala, & Indrikis Krams (2012) You mob my owl, I’ll mob yours: birds play tit-for-tat game.Scientific Reports 2, Article number: 800, doi:10.1038/srep00800


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