Acorn Woodpecker, Melanerpes formicivorus

Photo above: Acorn woodpecker in the Douglas Family Preserve, 11/6/22, 2:21pm, weather: cloudy.  This woodpecker was among several  that were drilling holes in this dead tree trunk, which is located outside of a small eucalyptus grove near the bluff.  It had a red head like most acorn woodpeckers, but this did not show in the picture.This tree has been active with woodpeckers for at least a decade, and is filled with holes and acorns all the way down to the ground.

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Species Profile

DIET: Acorns, nuts, insects, sap, fruit.

PREDATORS: Hawks

HABITAT/RANGE:  Mainly oak woodlands but also other environments where oaks exist nearby, including suburban areas.  Their range extends along Western North America from Oregon to Central America.

CONSERVATION STATUS: Least concern.  
WHERE TO OBSERVE IN SB: Douglas Family Preserve, Stow House (at Lake Los Carneros), Parma Park, oak woodlands

Source: All About Birds, Animalia, Collier et al.

If you've ever seen an array of acorn-containing holes in a dead tree or the wooden eaves of a building, you were probably looking at the work of acorn woodpeckers.  These birds are a native species here in Santa Barbara (and down the West Coast all the way through Central America) and commonly inhabit areas where oak trees dominate.

Appearance

Acorn woodpeckers are easily recognizable by their striking colors, loud screeching or nasal-sounding calls (listen here), and habit of drilling holes in wood.  They are about the size of a jay, and are mostly black with a white underside, cream-colored patch under their eyes, and red cap.   Their eyes, unlike other species of woodpecker, have a white iris.  They have a pointed, chisel-like beak that they use to make holes in trees for nesting and acorn storage. 

Source: Birdfact

Species History

Acorn woodpeckers are among the melanerpine woodpeckers (genus Melanerpes), a subgroup of the family Picidae, which includes all woodpecker species as well as similar birds like sapsuckers. Among the closest relatives of acorn woodpeckers are Lewis's woodpeckers (Melanerpes lewis), which are present but uncommon in Santa Barbara, and red-headed woodpeckers (Melanerpes erythrocephalus) in the Eastern US.

 

Acorn woodpeckers are currently increasing in population and are listed as Least Concern.  Their tendency to store acorns in manmade structures (such as Stow House in Goleta) is one demonstration of their adaptability to human presence. However, oak trees providing acorns are an essential part of their habitat, and when those are lost to urbanization, woodpeckers may be pushed out of areas.  Additionally, human-introduced birds like starlings can negatively impact them by competing for nest cavities.

Sources: AnimaliaKern Audubon SocietyiNaturalist

Behavior

Acorn woodpeckers are highly social birds, existing in family groups of 10-16 individuals that cooperatively forage and defend their territory.  When acorns are ripe in the fall, woodpeckers store them in granaries- collections of small holes that they drill in trees (or manmade wooden structures) with their sharp beaks.  All the woodpeckers within a flock will share the same granaries and defend them from jays, squirrels, and other potential acorn thieves. 

While acorns (and sometimes other nuts) make up about half of their food supply, coming in handy as backstock when other food sources are not as plentiful, acorn woodpeckers also feed on insects, fruit, and sap.  Woodpeckers mainly eat insects like ants that crawl on the outside of tree bark, and sometimes also catch insects mid-flight as a bat would.  The sap that they feed on comes from the holes they drill themselves, or also from holes previously made by sapsuckers.

Woodpeckers share nesting cavities as well as granaries within their group.  These cavities are usually made in dead wood.  Sometimes multiple females lay eggs around the same time, and the resulting 3-7 eggs in the nest will hatch chicks from different mothers.  In other cases, the most recent female to lay eggs will destroy all previously laid eggs in the nest before laying her own.  Regardless, all the woodpeckers in a colony will then help incubate the eggs and raise the chicks.  

 

Sources: Kern Audubon SocietyAudubon

Can Woodpeckers Damage Your Trees?

Just because you may have seen dead trees full of woodpecker holes during a stroll in a local open space doesn't mean your own backyard trees will die if used by woodpeckers as granaries.  Healthy trees can typically tolerate woodpecker activity just fine, and woodpeckers actually prefer trees that are already dead anyways because the wood is easier to drill holes in.  (That said, if you notice a particular tree in your yard being used by a lot of woodpeckers, this could be a sign that it is already weakened by other issues like disease or lack of water and you may want to consult an arborist.)

While woodpeckers drilling in trees is typically not harmful, what can cause damage is when they try to store their acorns in manmade structures, like the eaves of your house.  To discourage them from doing this, try filling the holes with putty so they can't use them, temporarily covering areas with burlap while woodpecker activity is high (e.g. during acorn season), or hanging reflective material like Mylar strips around the area.  Painting rather than staining wood has also been shown to reduce its appeal to woodpeckers.  

Never use sticky "bird repellent" products to manage woodpeckers or other birds.  While many of these are marketed as nonlethal repellents or deterrents, they run the risk of unintentionally trapping or fatally injuring the birds.

Sources: All About BirdsPenn State Extension

Ecological Roles

By collecting and storing acorns, acorn woodpeckers play an important role in seed dispersal of oak trees, as they lose some acorns while bringing them to their granaries.  Additionally, the tree cavities that they create for their nests may later provide homes for other species, known as secondary nesters (the woodpecker would be the primary nester).  These species may include other birds, such as nuthatches, as well as mammals like squirrels.

Sources: Lake Metro Parks, Drake et al.

How to Observe Woodpeckers

An oak woodland is the best type of habitat in which to observe acorn woodpeckers, and fall is the ideal season because the acorns are ripe and woodpeckers are stocking up their granaries.  Stow House in Goleta supports a very large woodpecker population, and the oak woodlands of the Douglas Family Preserve or the lowest part of Parma Park also provide good viewing opportunities.  Stand still in the midst of the oaks, with or without binoculars, and you may see a woodpecker climbing up the trunk of a tree or even upside down under a branch.  Listen for their screeching calls and the persistent drumming of their beaks on the wood.