Melanerpes formicivorus
Often dubbed the “clown-faced woodpecker”, acorn woodpeckers are distinctive red-crowned woodland birds found along the Pacific Coast of the United States. As well as their striking appearance, they are known for their intricate carpentry work to create “granaries” in trees for storing acorns.
Acorn Woodpecker
Female Acorn Woodpecker
Acorn Woodpecker pushing an acorn in to a tree trunk
Acorn Woodpecker perching on a broken branch
The plumage of acorn woodpeckers is unmistakable, and unlikely to be confused with other species.
Males have a solid red cap, a rich black and white face, white eyes surrounded by a black mask, a white forehead, chin, and cheeks, and black markings around the base of the bill.
Acorn woodpeckers have a solid black back and tails are solid black, with some greenish feathers. The wings are black with a rounded white wing patch. A white rump is visible in flight. The breast is white, heavily streaked with black, particularly the upper breast, which fades into a white belly and underparts.
The acorn woodpecker has a long, sharp, black bill and black legs and feet.
Male Acorn Woodpecker
Female Acorn Woodpecker
Female acorn woodpeckers are similar to males, although usually slightly smaller. The key difference between the sexes is in females, a black band separates the white forehead from the bright red cap. In females, a smaller area of red is present, towards the rear of the crown.
Juvenile acorn woodpeckers are duller in color than adult males but have similar markings, with dull red coloring visible on the crown. Their eyes are initially dark but gradually lighten to white within the first three months.
Portrait of a Male Acorn Woodpecker
Portrait of a Female Acorn Woodpecker
A medium-sized member of the woodpecker family, acorn woodpeckers are larger than downy woodpeckers but slightly smaller than northern flickers and hairy woodpeckers. Females are usually marginally smaller than males.
Acorn Woodpecker at nest cavity in Sycamore tree
As well as their “comical” appearance, acorn woodpeckers have a call that sounds a lot like cackling laughter. Other vocalizations include a loud ‘waka-waka-waka’ call, heard as a contact call or showing territorial boundaries. Noisy trilling and chattering notes from groups are also common.
Two Acorn Woodpeckers on a branch chattering
Despite its name, an acorn woodpecker’s chief food source is insects, particularly flying ants. A sallying technique to catch prey in mid-flight is used, with acorn woodpeckers watching for suitable flying insects from the upper branches of tall trees.
Acorns are eaten in large numbers, plucked directly from trees, and occasionally collected from the ground. These are stored in holes drilled in dead tree trunks and snags and used as a backup source of food throughout the year. Other foods include sap, catkins, sunflower seeds, mice, birds’ eggs and bats.
Acorn woodpeckers do depend on acorns as a source of food, although insects form a more important element of their diet. They drill acorn-sized holes in tree trunks, and post acorns into them, forming ‘granary’ stores. Once an acorn has dried out, it is then moved to a smaller hole, a considerably time-consuming process, but creates a valuable stash of food for times when insects and other foods are in shorter supply.
Young acorn woodpeckers are fed with small acorn pieces and insects, such as beetles, flying ants and wasps. As nestlings grow, their dependence on acorns increases, with adults raiding their granary stores to keep up with the feeding demands.
Acorn Woodpecker feeding in the forest
Oak woodlands meet all the habitat requirements of acorn woodpeckers for both their foraging and nesting needs. Mixed woodlands, with oaks alongside pine trees, are also a popular choice. Urban and suburban parks with oak trees are also increasingly common environments for sightings.
Acorn woodpeckers are present from sea level up to elevations of around 4,000 m (13,000 ft) in the Andes. Sightings are more prevalent in hilly or semi-mountainous terrain.
Acorn woodpeckers are only found in a limited geographical area on the west coast of the US, stretching along the coast of Washington, Oregon, and California. To the south, they spread throughout the oak forests of Central America, reaching Colombia in the south.
Check out this in-depth guide for more information on the Acorn Woodpeckers range and habitats.
The presence of oak trees is the key factor for acorn woodpeckers when establishing a territory, and because their yearly crops are subject to variation from year to year, populations are fairly fluid. California is said to be the heart of the range, where acorn woodpeckers are both a widespread and common resident species.
Within their range, acorn woodpeckers are considered widespread and abundant, and in regions where they are present, they are often the most common woodpecker species, especially in regions dominated by oak woodlands. The overall population is estimated to be around 7.5 million individuals.
Acorn Woodpecker in forest habiat
The only acorn woodpeckers in the US are isolated populations found in Washington, Oregon and California. Occasional reports are recorded of individual vagrants and small populations further inland, across the southwestern states of Arizona, New Mexico, Colorado, Nevada, Oklahoma, Texas and Utah.
Occasionally, acorn woodpeckers cross the border from Washington into British Columbia, but no major populations have been established in Canada yet.
Acorn Woodpecker in a forest
The average lifespan of an acorn woodpecker is estimated at around 9.5 years, with the oldest recorded individual reaching 17 years and 3 months.
Breeding is possible from one year of age, but due to the cooperative breeding seen in this species, it is not unusual for young birds not to breed until they reach 4 or 5 years of age, instead helping raise the young of other birds in their group.
Cooper’s hawks are thought to be the largest natural threat to acorn woodpeckers in the United States, with adult birds targeted as well as nestlings and juveniles. Bull and gopher snakes raid nest cavities, taking eggs, young and brooding adults.
Under the Migratory Bird Treaty Act of 1918, acorn woodpeckers are protected in the United States. It is a federal offense to deliberately kill, injure, trade, or trap an acorn woodpecker or to destroy, damage, or trade their eggs or young.
Globally, acorn woodpeckers are classed by the IUCN as a species of least concern. Loss of habitat and degradation of woodland landscapes is a concern for the future survival of the species.
Female Acorn Woodpecker foraging in natural habitat
Nest cavities are excavated in large, mature trees which are either already dead or beginning to decay. Both male and female acorn woodpeckers are involved in chiseling out the chambers, and multiple cavities are constructed in the same territory, so those not used for nesting can be used for overnight roosting.
It’s common for previously used nests to be chosen again in future seasons, with up to 50 percent of nests reused each year. Wood chips line the base of the chamber, but no additional nesting material is added.
Egg-laying for acorn woodpeckers begins in April (or on rare occasions, from as early as late March), and extends until June or July. May is the peak month for eggs to be laid. Occasionally, a second brood is laid later into the fall, in years where acorn crops are particularly abundant.
Incubation lasts for 11 days and is shared between the male and female.
Between 3 and 7 eggs are laid, each measuring 2.5 cm (1 in) by 1.9 cm (0.8 in). Eggs are whitish in color and lack any markings.
Mating and pairing habits of acorn woodpeckers are varied and complex, with some populations forming seasonally monogamous pairs, while in others, cooperative breeding is most common.
Acorn woodpeckers do not form lifelong pair bonds, but it is usual for them to remain in large social groups, with multiple individual birds involved in raising the young.
Typically, acorn Woodpecker communities contain between one and seven male breeders. These compete for matings with up to three different females, and several females may lay eggs in the same cavity. All non-breeding members of these social groups will take a role in incubating eggs and feeding and protecting the young.
Acorn woodpecker bringing food to the nest to feed its young
Acorn woodpeckers are cooperative breeders, living in close proximity to others of the same species, and working together to create vast caches of acorns in holes they drill in decaying tree trunks and branches.
Some competition may occur between breeding females, and the eggs of rivals may be destroyed before incubation starts.
Overnight roosting spots used by acorn woodpeckers are typically disused holes in tree trunks, where they can rest without the threat of being disturbed by predators and are safe from any weather damage.
Acorn woodpeckers are famous for their habit of creating granaries in which they can store dozens of acorns which they then use as emergency food supplies when the availability of insects runs low. Caching acorns ensures there is a plentiful and immediate supply of food when hungry nestlings need to be fed.
Acorn woodpeckers certainly make their mark when creating their granary holes in trees, drilling deep cavities in which to hide acorns. Up to 50,000 holes may be created in a single tree, and one report counted 700 lb of acorns that had been stashed in holes in the wall of a building.
As the trees used are most commonly already dead or dying, it might be argued that the granaries created by these hard-working woodpeckers shouldn’t really be classed as ‘damage’.
Two Acorn Woodpeckers storing emergency food supply
Acorn woodpeckers are non-migratory and remain in the same territories all year round. They may relocate short distances in search of a more plentiful supply of acorns if trees in the immediate locality have not had a fruitful year and they haven’t been able to build up a sufficient supply in their ‘granary’ stores.
Native to the extreme western regions of the US, acorn woodpeckers are only found in the Americas, with their usual range extending from Washington in the north southwards through Oregon and California, into Central America, and reaching the coast of Colombia in South America. They are not found in the wild in other parts of the world.
Acorn Woodpecker in woodland
The Migratory Bird Treaty Act of 1918 offers protection to acorn woodpeckers, their nest sites, eggs, and young. This legislation safeguards the species against being killed, injured, taken into captivity, or sold to the pet trade.
A rich supply of acorns and an availability of decaying or dead trees is the perfect combination for attracting acorn woodpeckers. Areas with oak trees alongside open land for foraging for insects are also important to allow acorn woodpeckers to catch prey in mid-air.
Acorn woodpeckers are so named for their unique behavior of storing acorns in tree trunks, by drilling a series of deep holes in rotten wood and creating caches as future food stores. Acorns are not their main food source, however: the second part of the species' Latin name “formicivorus” is possibly more accurate, as it means ‘ant-eating’.
Length:
19cm to 23cm
Wingspan:
35cm to 43cm
Weight:
65g to 90g
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