Would you believe me if I told you that acorn woodpeckers get married, change their kids’ diapers, use day care and can predict the weather?

I’d love to tell you I just made all that up. But it’s true, all of it.

Acorn woodpeckers have some of the most complex social behavior recorded of any vertebrate species (animals with backbones) in the world – including humans. Considering there are over 64,000 vertebrate species on the planet…that’s really saying something.

(If your jaw just dropped that’s ok – it happened to me too.)

Who knew, right? Some of the most sophisticated creatures in the animal kingdom are flying through our open spaces, slamming their heads against big oaks and nearby telephone poles.

Skeptical? Let’s break it down. What is it about these birds that makes their social structures so complex?

For starters, they all live under one roof. Unlike most birds, acorn woodpeckers live in family groups called “clans” that consist of 2-16 members. These clans are broken into three groups: breeding females, breeding males and nonbreeding adult children.

This is where it starts getting really complicated. They call it “polygynandry” (say that ten times fast), which means that breeding females mate with any of the breeding males, and vice versa. To add to the intimacy, the females all lay their eggs in the same nest and the whole family helps raise the youngsters. As a father of two myself, it must be nice to have built-in daycare.

They get married too. Well, sort of. There’s no ceremony or fancy cake, but they commit to each other for life. Not just to other individuals, but to the entire clan. Males and females will wait until their partners have either died or disappeared before accepting new mates.

It’s gotta be tough for the non-breeders in the family. For them, it’s just a waiting game. They’ll stay with their family for up to five years while constantly looking for an open spot in a neighboring clan. It must be exhausting, especially if you’re helping raise the kids too.

You’re probably wondering about the diaper thing. I wasn’t kidding. When an acorn woodpecker chick eats food delivered by one of its parents, it conveniently produces a “fecal sac” a few seconds later. The adult bird just has to wait a few seconds for the sac to emerge and then, boom, out of the nest it goes. Talk about efficiency!

Ok, their ability to predict the weather might be a bit of a stretch.

The story goes that two or three days before a storm, acorn woodpeckers get busy hammering their acorns into the bark of nearby trees, probably making sure they are nice and secure before the storm arrives. Maybe there’s something to it? If you hear more hammering than normal, check the forecast. You might be surprised, there’s more to these birds than you might think.


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Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 87,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more

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