Acorn Woodpeckers

February 28, 2018  •  1 Comment

This clown-like bird, called an Acorn Woodpecker,  is a mighty interesting species!  It practices some social and feeding behaviors that are very unusual as well as being a fun, colorful bird to observe. 

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Unlike most woodpeckers, when you find one you will usually find a flock made up of a small group of mating birds and other younger non-reproducing birds. All of their activity will be centered around a few trees that are vital to their existence.  A family unit drills thousands of holes into each tree, which they then fill with acorns and other nuts. These trees are call "granary" trees and according to the Cornell Lab, can contain 50,000 nuts in one tree. 

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The Acorn Woodpecker harvests an acorn and flies to a granary tree where it searches for a pre-drilled hole that is the perfect size for the acorn so it fits snuggly and won't fall out.  As the acorn dries, it might loosen, so the Acorn Woodpecker are constantly tending the tree, moving acorns around to appropriate-sized holes. Basically, they are farmers tending their crops. 

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Why do they do this unique food-fathering behavior?  Acorns are rich in fat and will help the family survive cold winters. By having a granary tree the loss due to pillage by other birds and animals is minimal as they are guarded carefully by the flock. Because they are tended they are eaten before they become moldy. Loss is minimal.  If some hatch worms, then the worms are eaten. 

The Cornell Lab of Ornithology reports that this behavior sometimes leads to acorns stowed in places they can’t reach them. In one instance, researchers found 485 pounds of acorns in an Arizona water tank.

Acorn Woodpeckers also eat a variety of other foods and like many woodpeckers that includes insects often caught while in the air like a Flycatcher. 

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The social lives of these woodpeckers may be even more fascinating than their "farming" behavior. Researchers at Cornell has been studying them since 1974; this long-term study continues to reveal the intricacies of an acorn woodpecker family unit.

“The mating system of this species is one of the most complex of any vertebrate, with social units consisting of up to seven related males competing for matings with up to three related females, all laying eggs in a single nest, and up to 10 nonbreeding helpers of both sexes (offspring from prior years).” Young birds stay in the family for several years before dispersing which helps reduce inbreeding.   

Sometimes this family unit behavior becomes very interesting........and really weird!  Multiple females lay eggs in the same nest.  When one of the females, who has not laid eggs yet, discovers eggs in the nest she removes them and all family members dine on them.  More eggs are laid and the process of removing and eating eggs is repeated.  What's going on?  The first hatched has the best chance at survival and each female wants her eggs to the first to hatch so she removes eggs laid before hers. Over several seeks they get on the same scheduler and lay their eggs on the same day and all are happy and no more canibalism takes place.  

Who knew how interesting and complex one species could be?  

 

 


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Pamela Graber(non-registered)
yikes
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