How did shrikes learn to impale their prey?

Author Liz Kalaugher discusses how shrikes developed their signature skewering technique.

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Red-backed shrike

Shrikes (here a red-backed shrike) are the thorn in the side of many small mammals © Prisma Bildagentur / Getty

 

These hook-beaked birds are known for skewering their
insect and other small prey onto
spikes such
as thorns and
 barbed wire.

They may have
 developed the
 technique by
 accident, when
 prey they were
wedging into 
forks of branches to manipulate, perhaps 
because they lack strong 
talons, became stuck on
 thorns.

By repeatedly using 
the same spikes, the birds ended up with caches of food. Nowadays, males use these food stores, along with display items such as rags, snail shells and the membrane-coated faecal sacs produced by nestlings, to attract females.

Males with bigger caches tend to breed with the earliest-arriving females, producing more fledglings. They may even win two mates. By caching, a bird can mark his territory, hoard supplies for leaner times and store toxic prey, such as lubber grasshoppers, until the chemicals they contain decompose.

The development of this technique may also have been an accident, with males first impaling the vivid insects to attract mates before later discovering that they became safe to eat.

 

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