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October 2019
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DID YOU KNOW...why Catalina's Acorn Woodpecker is not your average bird?
Just because you see them everywhere doesn’t mean they’re not cool. In fact, it’s all the more reason to tell your guests about them! Need another reason? Acorn Woodpeckers are actually one of the most interesting birds in North America. Why? Read on.
  • The Acorn Woodpecker has a very complicated social system. Family groups hold territories, and young woodpeckers stay with their parents for several years and help the parents raise more siblings. Most birds don’t engage in this kind of cooperative behavior.

  • Several different individuals of each sex may breed within one family, with up to seven breeding males and three breeding females in one group. Strange but true!

Issue #1 / All About Bison

History on Catalina
By the numbers
Secret sex lives
Fact or Fiction?
Did you know...

  • All members of an Acorn Woodpecker group spend large amounts of time storing acorns. Acorns typically are stored in holes drilled into a single tree, called a granary tree. One granary tree may have up to 50,000 holes in it, each of which is filled with an acorn in autumn.

  • The Acorn Woodpecker will use human-made structures to store acorns, drilling holes in fence posts, utility poles, buildings, and even automobile radiators. Occasionally woodpeckers will put acorns into places where it cannot get them out. Woodpeckers were once recorded putting 485 pounds of acorns into a wooden water tank in Arizona!

  • Acorn Woodpeckers rely on their stored acorns to survive (and thrive) in times when insects are unavailable.

  • There is no evidence that supports the idea that acorn woodpeckers “intentionally farm” granaries in order to cultivate insects for food. The acorns themselves are the crop.

  • Perhaps the most amazing thing about these birds? In groups with more than one breeding female, females put their eggs into a single nest cavity. A female usually destroys any eggs in the nest before she starts to lay. In fact, more than one third of all eggs laid in joint nests are destroyed. Once all the females start to lay at the same time, they stop removing eggs and begin incubating. Why on earth would they do that? It’s so the young will hatch at about the same time. Chicks of the same age are significantly easier to provide for than different aged birds that each might require different sized insects. On Catalina Acorn woodpeckers can be seen tending granaries in palms, dead pines and other trees. They are easily seen on Avalon Canyon Road on the walk from town to the Wrigley Memorial and Botanic Garden.

  • They nest in cavities, which are typically used for many years.

  • Acorn Woodpeckers eat mostly insects when available, but also rely on acorns that are in plentiful supply in the oak-covered wild lands of Catalina.

  • Though it’s rare, Acorn Woodpeckers are one of the few bird species that can nest in the fall! When this occurs it appears to be linked to “good acorn years.”

For the Science Minded
Acorn Woodpecker Taxonomy
Phylum: Chordata
Class: Aves
Order: Piciformes
Family: Picidae
Genus: Melanerpes
Species: Melanerpes formicivorus
Common name: Acorn Woodpecker
Habitat: oak woodlands
  • Acorn Woodpecker. (2009). In The Cornell Lab of Ornithology.
  • Ehrlich, P. R., Dobkin D. S., & Wheye, D. (1988). The Birder’s Handbook: A Field Guide to the Natural History of North American Birds. Ney York, NY: Simon and Schuster.

Did you enjoy this edition of The Island Naturalist, and think you know someone else who might also? Click here to schedule a Catalina Island Conservancy Naturalist Training so that you both can enjoy true stories from Catalina's wildlands each month.

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