Bird Profile

Acorn Woodpecker

A loud, white-eyed woodpecker that drills a dead limb full of holes and wedges an acorn into every one of them, then defends the whole thing with its extended family.

The Acorn Woodpecker (Melanerpes formicivorus) has a face that looks designed by committee: a red cap, a white forehead running into white cheeks, black around the bill, and a staring whitish eye that gives the whole arrangement a fixed, slightly manic expression. Groups of them yell at each other from oak snags in a raucous, laughing waka waka waka that carries across a whole canyon.

Two things make this bird genuinely unusual, and both matter to anyone hoping to see one in a yard. The first is the granary: a dead limb, snag, utility pole or wooden wall drilled full of individual holes, each holding one acorn wedged in tight. A single well-used granary can carry tens of thousands of stored acorns, and counts running to around 50,000 holes have been reported in long-established trees.

The second is that they live in groups. An Acorn Woodpecker territory is held by an extended family, often somewhere between three and fifteen birds, with several breeding males, one to three breeding females, and grown offspring from earlier years staying on as helpers. The granary belongs to the group, is defended by the group, and is passed down across generations.

The practical consequence is blunt and worth saying up front. This is one of the few common feeder-visiting woodpeckers you cannot attract with food. Whether you get Acorn Woodpeckers is decided by whether your neighborhood has oaks and a granary site, not by what you hang up.

How to identify an Acorn Woodpecker#

Medium-sized and boldly patterned: black above and across the chest, white belly, and in flight a white rump and a white patch at the base of the primaries that flashes hard against the black wing. On the head, a white forehead and chin, black around the eye and bill, red on the crown, and a pale, staring iris.

• Male: the red crown runs forward and meets the white of the forehead directly.
• Female: a black band separates the white forehead from the red at the back of the crown.
• Juvenile: dark eyes rather than whitish, and a mostly red crown regardless of sex.

In its range the confusion species are few. Northern Flicker is brown and barred with a spotted belly. Downy and Hairy Woodpeckers are black and white with a white back stripe and no red on the crown except a small nape patch on males. The Red-headed Woodpecker of the East has a completely red head with no white face pattern, and the two ranges barely meet. The wider sorting exercise is in the woodpecker identification guide.

The granary, and why the whole bird depends on it#

Acorn Woodpeckers store food in a way no other North American bird does. Rather than scattering caches, the group drills a dense array of shallow holes into thick bark or dead wood and hammers a single acorn into each one, pointed end in, so tightly that squirrels and jays cannot pull them out easily. Favored substrates are dead limbs, snags, thick-barked pines, sycamores, utility poles, fence posts and, unfortunately for some homeowners, wooden siding.

Maintenance is constant. As acorns dry they shrink and loosen, so birds pull them out and move them to smaller holes, and much of a group's autumn and winter work is this shuffling. Members take turns guarding the granary against Steller's Jays, California Scrub-Jays, squirrels and other Acorn Woodpecker groups.

A granary is a long-term investment. Because it takes years of drilling to build, groups defend theirs fiercely and stay on the same territory for generations. It also explains why acorn crop failures are serious for this species: a poor mast year across the local oaks can push a whole group to abandon a territory it has held for decades.

Living in groups: who breeds and who helps#

Cooperative breeding in this species has been studied in California for decades, and the arrangement is genuinely strange. A group typically contains several co-breeding males, usually brothers, and one to three co-breeding females, usually sisters, all sharing a single nest cavity. Offspring from previous years often stay on for a year or more as non-breeding helpers, feeding nestlings and maintaining the granary rather than dispersing.

Where two or three females share a nest, each removes and destroys eggs laid by the others until they begin laying in synchrony, after which the destruction stops and all the surviving eggs are incubated together. It is a costly-looking system that appears to resolve into a workable compromise, and it is one of the better-documented cases of joint nesting in birds.

For a yard observer, the visible result is that Acorn Woodpeckers arrive in company. A single bird at a suet feeder usually means several more within earshot, and the noise level is the giveaway long before you see them.

Why suet alone will not bring them in#

Most feeder woodpeckers can be recruited. Put up a suet cage in the right region and downies, flickers and red-bellies will generally find it, as set out in attracting woodpeckers. Acorn Woodpeckers do not work that way, for three reasons.

1. They are habitat specialists. They need oaks, and they need enough of them across a defended territory to carry the group through winter.
2. They need a granary substrate. Standing dead wood, thick-barked pines or old snags are effectively required infrastructure, and a suburb that removes every dead limb removes the housing stock.
3. They are territorial residents, not wanderers. Groups hold ground year-round and rarely prospect widely, so there is no floating population to recruit with a feeder.

So the honest answer to whether you can attract them is: if you already live inside or beside occupied oak woodland, yes, easily. If you do not, no amount of suet will change it. What you can do is make an occupied territory better, mainly by leaving dead wood standing, as argued in snags and dead wood, and by keeping or planting oaks per native plants for birds.

What they will take at a feeder#

Where a group is present, Acorn Woodpeckers use feeders readily and noisily. Their natural diet is broader than the name suggests: stored acorns are winter food, but they also spend a great deal of the warm season flycatching from exposed perches, drinking sap from wells they drill themselves, and taking fruit.

Suet selection matters less than mounting. A cage screwed flat to a trunk or a post suits a bird that habitually clings to vertical bark, and the options are compared in suet feeders and the suet guide. For nuts, a platform is easier for a bird this size than a small mesh tube, and the choices are in peanut feeders and platform feeders.

Sap wells, flycatching and the rest of the diet#

Calling this bird an acorn specialist undersells it. Stored acorns are the winter bank, but through spring and summer Acorn Woodpeckers spend much of the day flycatching, launching from a bare branch to snatch flying insects and returning to the same perch, more like a large clumsy flycatcher than a woodpecker. Ants, beetles and other insects are taken off bark and from the ground as well.

They also drill neat rows of shallow sap wells in the bark of oaks, willows and other trees and return to drink the sap, along with any insects the sap traps. Fruit gets used heavily in late summer, and in some areas they take grass seed and even the odd bird egg. Acorns dominate the storage economy because they keep, not because they are the only thing on the menu.

When they drill your house#

Acorn Woodpeckers do sometimes turn wooden siding, trim, eaves and utility poles into granaries, and a wall packed with acorns is an expensive problem that also draws rodents. It usually happens where natural granary substrate has been removed and a house offers the nearest equivalent.

A realistic plan#

1. First establish whether the birds are already local. Listen for the laughing waka waka calls and look for a limb or pole peppered with holes.
2. If they are present, mount a suet cage flat against a trunk and add shelled nuts on a platform.
3. Expect a group rather than a bird, and expect them to be loud.
4. Leave dead limbs and snags standing wherever it is safe to do so.
5. Protect and plant oaks, ideally more than one species.
6. Keep an eye on the nectar feeder, and add a second for the hummingbirds if needed.
7. If they start on the house, exclude and repair rather than trying to remove birds.

If they are not local, this is a bird to travel for rather than to wait for. Oak woodland across California and the Southwest holds them in numbers, and the same woodland is where you will find Oak Titmice and scrub-jays working the same acorn crop from a different angle.