Acorn Woodpeckers (Melanerpes formicivorus) are quite distinctive from other woodpecker species: They are communal. How did the cooperative behavior evolve? Biologists are working on answers for this curious question.
Evolution of cooperative behavior is a matter of game theory and has been encapsulated in a 1987 BBC documentary called “Nice Guys Finish First” by Richard Dawkins. One of the most ubiquitous example for cooperative behavior comes from ants. Why do certain individuals altruistically give up their reproduction and help others?
Acorn woodpeckers live in oak and mixed oak-conifer forests on slopes and mountains in the Southwest and West Coast of North America. They and can be watched easily since they’re tolerant of humans. They can be observed in places where there are acorns and suitable trees to store them. They store impressive numbers of acorns in what is called “granary” trees. A typical granary tree contains hundreds or even thousands of acorns. The largest on record contained around 50,000. Almost every square inch of the tree’s trunk and limbs may be covered with acorn-filled holes. Granaries are constructed by multiple generations of birds containing thousands of pecked holes to accommodate acorns for storage. These granaries are guarded at all times.
Just like other cooperatively breeding animals such as Meerkats, Acorn Woodpeckers’ family interactions are interesting as well. Acorn Woodpeckers live in busy family groups numbering up to 15 adults. They appear to work together and raise their chicks cooperatively one nest.
Biologist Walter Koenig of Cornell University, has been studying Acorn Woodpeckers at the Hastings Natural History Reservation in Carmel Valley, California for more than 40 years. Every summer, Koenig and his colleagues visit their study site and carry out census activities. They climb trees to capture and mark hundreds of new woodpecker chicks with colored leg bands. These bands allow identification of individuals and families year after year. They also take blood samples for parentage analysis to see mating patterns. Some individuals are fitted with radio transmitters (see the antenna swinging behind some birds in the featured film) that allow tracking movements.
They have discovered a waxing and weaning relationship between cooperation and conflict within these woodpecker families. The continuous dataset the researchers have gathered over four decades is beginning to produce answers to one of evolution of cooperation.
There’s more to add to the story of these birds. Cartoon animator Walter Lantz claimed that Woody Woodpecker, was inspired by Acorn Woodpeckers. In 1940, Lantz married actress Grace Stafford. According to Lantz’s account, during their honeymoon a particularly insistent individual wouldn’t stop pecking on the roof of their cabin! Grace suggested that Walter use the bird for inspiration as a cartoon character. Taking her advice, Lantz debuted Woody Woodpecker in a short, “Knock Knock”. Lantz liked the results and built a series around it. Mel Blanc supplied Woody’s voice for the first three cartoons. Blanc’s halmark laugh was used throughout the entire series.
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