Such dramatic group displays frequently happen during territorial encounters and boundary disputes. At the other end of the spectrum, though, are what one researcher termed “ waka gatherings” in which several group members converge on the same spot, all displaying noisily, thereby attracting the attention of others until the whole group has assembled. In its mildest form, the call occurs with the wings held only slightly open. It is commonly seen when group members land near each other, in which case it probably acts as a greeting. This behavior occurs in a number of contexts and at various levels of intensity. The most dramatic is the “ waka display” in which the bird stridently calls waka-waka-waka while spreading its wings to show its bold white wing patches. Furthermore, each youngster might have been related to him differently.Īs one might expect from such a socially complex species, the Acorn Woodpecker uses a wide array of calls and displays to communicate with the members of its group. In a monogamous species, he undoubtedly would have been their father, but in this case, he might have been their father, uncle, or older brother. Late one summer, I photographed two fledgling Acorn Woodpeckers begging for food from an adult male. Several (up to 7) co-breeding males (often a coalition of brothers) breed with 1 to 3 joint-nesting females (often sisters), which lay their eggs in the same nest hole.įurthermore, there are nonbreeding helpers, often the breeders’ grown offspring from previous years, which join in to feed the young, thereby helping raise their own younger siblings. Research in Central California by Cornell Lab senior scientist Walter Koenig shows that same-sex breeders are usually closely related. First, in any group there may be more than one breeder of each sex, in a mating system known as polygynandry. Acorn Woodpecker society has a double layer of complexity. These elaborate interactions reflect the species’ complicated social structure. Just as the kitchen tends to be the hub of our own family lives, the granary is the place for regular Acorn Woodpecker get-togethers, typically noisy affairs with dramatic displays. They also eat insects, including many flying insects that they catch on the wing during sally-flights from a high perch, like a flycatcher. Is something affecting their populations?ĭuring winter, the stored acorns form much of the birds’ diet, but at other times of year Acorn Woodpeckers also feed on tree sap, oak catkins and other tree flowers, and fruit. An entire family group may rally to defend against such potential acorn thieves as squirrels and jays, as well as against other Acorn Woodpeckers from outside their group. The Acorn Woodpecker is unique in having a centralized food store constructed and defended communally. Almost every square inch of the tree’s trunk and limbs may be covered with acorn-filled holes, the cumulative result of multiple generations of individuals each drilling more and more every year. A typical granary tree contains hundreds or even thousands of acorns-the largest on record contained around 50,000. But no bird gets into hoarding on such a grand scale as the Acorn Woodpecker. The Acorn Woodpecker is not alone in stocking up on food for the winter-a number of other birds, including various species of jays, chickadees, nuthatches, and several other woodpeckers, also do it. I’m intently focused on a large tree trunk riddled with hundreds of holes, each containing an acorn-a typical Acorn Woodpecker granary tree. That explains why you might find me skulking around with my camera behind the restrooms of a certain California park that I’ve visited several times over the years. Living in close proximity to people, the bird is often unsuspicious and easily observed. It is relatively common in urban or suburban areas if oak trees are available. The species is found in western oak and pine-oak woodlands, preferring higher elevations, especially in Southern California where dense live-oak woodlands and oak savannahs are widespread. The most gregarious of all North American woodpeckers, throughout much of its range it lives in extended families of a dozen or more individuals, meaning that if you find one, you’re likely to find others nearby. What fascinates me more than its appearance, though, is the Acorn Woodpecker’s behavior-both its habit of hoarding numerous acorns as a winter food as well as its sometimes-dramatic social interactions. See more videos on the Lab’s Youtube channel.
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