- The Horsefield's bronze-cuckoo lays its eggs in the nests of other birds which most birds can usually identify as cuckoos before, but never after, the eggs hatch.
- However, superb fairy-wrens in Australia, who are bad at telling the eggs apart due to dark enclosed nests, have begun to adapt to recognize cuckoo hatchlings, and will leave them behind.
- To combat this, the Horsefield's bronze-cuckoos evolved to more perfectly match the calls of the fairy-wrens, rendering distinction almost impossible.
- With fairy-wrens unable to distinguish between egg type and hatchling call, it would seem that they would be doomed, but instead they just wait for the cuckoo to hatch.
- When the cuckoo hatches, it will push out all of the wren eggs,
and the parent wren will discover the true identity of the impostor, taking advantage of Australia's long hatching season and re-nesting.
I chose this story because it proved to be a good clear example of an evolutionary arms race. I also had never heard of birds tricking other birds into taking care of their young for them. Another thing i found interesting was how the hatched cuckoos instinctively pushed all of the other eggs out of the nest. How even innocent baby birds could turn out to be ruthless contenders in the arms race was quite amazing. What I learned from reading this was that an evolutionary arms race is not always just a battle between two traits in two organisms like with the salamanders and the snakes, but that the species in the race can employ a much sneakier and wider range of tactics too.
Sources:
- Owen, James. "Cuckoos, Wrens in Escalating Evolutionary Arms Race." Daily Nature and Science News and Headlines | National Geographic News. Web. 19 May 2010.
- Drew, Ray. "Birds of South Eastern Australia." Untitled Document. Web. 19 May 2010.
- "The Escalating Coevolutionary Arms Race between Cuckoos and Their Hosts : Living the Scientific Life (Scientist, Interrupted)." ScienceBlogs. Web. 19 May 2010.
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