These birds turn trees into huge acorn stores.
The woodpecker is one of the hardest working bird. Image credit: Ingrid Taylar
Unlike other woodpeckers, which peck insects out of trees, the acorn woodpecker has a completely different way of getting by.
Hoarding food for winter is definitely not unheard of among birds, but the acorn woodpecker’s habit of thoughtfully drilling holes in trees and placing hundreds of acorns in them is quite unique. Its complex feeding and (sometimes dramatic) social behavior make this busy hoarder probably one of the most interesting birds out there.
Besides impressive hoarding habits, acorn woodpeckers have an amazing social life as well. Image credit: Becky Matsubara
The acorn woodpecker is one of the 239 species of woodpeckers that make up the family Picidae. It can be found from the coastal areas of Oregon and California, all the way to Mexico and Colombia.
These birds prefer western oak and pine-oak woodlands on higher elevations, but they are also relatively common in urban and suburban areas. It’s likely that if you see one, you’ll find others soon, since they are organized in families of up to 12 individuals.
The family units live within a particular territory, and they nest communally. Their nests are usually built in large cavities in dead trees. Therefore, the activities of acorn woodpeckers happen around their tree and within the territory the family holds.
On the lookout. Image credit: Allan Hack
In family groups that have more than one breeding female, all females lay their eggs into a single nest, which results in strange events. When a female acorn woodpecker finds any eggs in her nest, the family will start eating them before every breeding female starts to lay eggs at the same time. According to Bill Schutt, Professor of Biology at LIU Post and a research associate at the American Museum of Natural History, this is to ensure that not only the oldest eggs have a chance to survive. “Presumably this is because the oldest hatchling would be the most likely to survive. To eliminate this advantage, the birds will keep eating each other’s eggs until they both lay their eggs on the same day, a process that can take weeks.”
Once the younglings mature into adults, they will stick around with their family for a couple of years to help out with the newborns. Eventually, they will fly off to look for a new family. Usually, they take the place of an adult that recently died.
Image credit: flythebirdpath
Acorn woodpeckers begin storing acorns for the colder winter months once autumn is right around the corner. All members of the family spend a lot of time collecting and hoarding acorns. They store the collected seeds in little holes drilled in a tree, called a “granary tree”. Any kind of tree will do, as long as it has a thick bark, but woodpeckers that live in suburban areas are more than comfortable drilling holes and storing their acorns in wooden poles as well.
Drilling all those holes is a serious job that requires a lot of precise planning. If the holes are too wide, the acorns can fall out of their place, or even worse, other birds may steal the stored goods. Leaving the hole too narrow is risky as well, since the acorn can break or deteriorate. First, the bird gently pushes the acorn into one hole after another, trying to find the perfect fit for the given acorn. Once the acorn is secured, it goes to put another one into place; and so it goes.
The work doesn’t stop there, though. The granary trees require constant tending and the members of the family group need to be on the lookout to defend their stash against potential acorn thieves, such as squirrels or even other woodpeckers. Therefore, one member of the group is always guarding their tree.
This tree has definitely seen a lot of woodpecker action. Image credit: brewbooks
An average granary tree usually holds thousands of acorns. The woodpeckers use every little square inch on the tree, which can be covered in holes from the bottom to the top. The most holes ever recorded on a granary tree were 50.000, which is the result of work done by multiple generations of woodpeckers.
Their evolutionary strategy has seemed to pay off: acorns are perfect for the winter months due to their rich fat content. And although no other bird hoards food on such a grand scale as the woodpecker, this habit is indeed effective for surviving cold weather without having to migrate to warmer climates.
Sources: 1, 2, 3
