Acorn woodpeckers are medium-sized birds found in oak woodlands of western North America. They get their name from their habit of storing acorns in holes they drill into trees. But acorns are not the only thing acorn woodpeckers eat. These social birds have a varied diet that includes insects like ants. In this article, we’ll take a closer look at the eating habits of acorn woodpeckers and whether ants factor into their diet.
Overview of acorn woodpeckers
Acorn woodpeckers (Melanerpes formicivorus) are black and white birds about 8-10 inches long. They have a black head, back, wings and tail, with a white forehead, throat, belly and rump. The males have a red cap on top of their head. Acorn woodpeckers live in small social groups that vigorously defend their territory. They are found in oak woodlands in parts of California, Oregon, Washington, Nevada, Arizona, New Mexico, Colorado, and Mexico.
Acorn woodpeckers are best known for their habit of making acorn granaries, which are holes drilled into dead trees or branches where they store acorns. Each acorn is precisely wedged into a hole to be eaten later in the year. A single tree can have thousands of acorn holes drilled by generations of acorn woodpeckers. The acorns provide an important winter food source for these birds.
Diet of acorn woodpeckers
Acorn woodpeckers are omnivorous, meaning they eat a varied diet of both plant and animal matter. Their diet includes:
– Acorns – One of their primary foods, stored in tree granaries for winter use.
– Other nuts and seeds – Such as pine nuts, almonds, hazelnuts, walnuts.
– Fruit – Berries, apples, cherries.
– Sap – They drill sap wells in trees to drink the sap.
– Insects – Including ants, beetles, caterpillars, grasshoppers, crickets, and others.
– Lizards and eggs – Small reptiles and eggs may supplement their diet.
Do acorn woodpeckers eat ants?
Yes, ants are part of the varied insect diet of acorn woodpeckers. They have been observed consuming both flying ants and ants found on the ground. Ants provide an important source of protein for acorn woodpeckers.
Some key points about acorn woodpeckers eating ants:
– Foraging on ground and trees – Acorn woodpeckers will forage both on the ground and in trees for ants and other insects. Their long sticky tongue helps them lap up ants on the ground.
– Variety of ant species – They have been noted eating different ant species, including carpenter ants, harvester ants, and honey ants.
– More ants in warmer months – Ant consumption may increase during warmer seasons when ants are more active and abundant.
– Not a primary food source – While ants are part of their diet, they do not depend on them as a primary food source like some other woodpecker species.
– Preference for ants with honeydew – Some observations indicate they favor ants that collect honeydew from aphids and scales because of the sweet honeydew coating on the ants.
Methods for finding and consuming ants
Acorn woodpeckers use several methods for finding and eating ants:
– Foraging on the ground – They will hop along the ground using their stiff tail feathers for support as they search for ants and other insect prey. Their long tongue helps collect ants.
– Probing in crevices – They will probe their bill into holes in trees and downed logs looking for carpenter ants and other wood-dwelling species.
– Flaking bark – Acorn woodpeckers can flake off pieces of bark to access ants underneath, using their chisel-like bill.
– Licking sap wells – Ants are attracted to the sap wells drilled by acorn woodpeckers. The birds will find ants gathered there looking for sap.
– Fly catching – When ants take flight, such as during mating flights, acorn woodpeckers will catch them in mid-air.
– Drilling into nests – They have been observed excavating into ant nests in dead trees to access the ants and larvae within.
– Rolling eggs – When raiding ant nests, they may roll eggs out of the nest chamber to access the ants trying to protect the eggs.
Ant defenses against woodpeckers
Ants have some defenses they can employ against predation by acorn woodpeckers and other insect-eating birds:
– Biting/stinging – Ants can inflict painful bites or stings as a deterrent. Some species like bulldog ants have powerful mandibles.
– Chemical sprays – Ants like carpenter ants can spray acids, sprays, or other chemicals at attackers.
– Nest defenses – Ants will fiercely defend the entrance to their nest from intruders. Some species have soldiers with large mandibles specifically for defense.
– Avoidance – Some ants are able to detect predators and flee to safety before being attacked. Fast-moving species are harder for birds to catch.
– Playing dead – Some ants display adaptive behaviors like thanatosis, where they curl up and feign death, to avoid being eaten.
– Tough exoskeleton – The external casing of ants provides protection from bird bills trying to crush them.
However, acorn woodpeckers and other birds have adapted to ant defenses with behavioral strategies like excavating into nests from the side or above, or rolling eggs away from nest entrances to access the ants inside.
Observations of acorn woodpeckers eating ants
There are many field observations that provide direct evidence of acorn woodpeckers eating ants as part of their varied diet:
Natural history accounts
Many natural history accounts describe acorn woodpeckers eating ants:
– Dawson (1923) noted their habit of breaking into the nests of carpenter ants to eat the ants.
– Bent (1939) wrote they are “very fond of ants” and will “break open ant hills” to access them.
– Beal (1911) observed them eating ants from the boughs of oak trees.
Studies of feeding behavior
Scientific studies analyzing the feeding behavior of acorn woodpeckers have revealed they consume ants:
– MacRoberts (1970) found they ate ants from five different genera, especially favoring honey ants.
– Bleitz (1957) found ants formed over 3% of their dietary intake from spring through fall in California oak groves.
– Tarvin (1999) filmed acorn woodpeckers disturbing carpenter ant nests and eating the ants flushed out.
First-hand accounts
There are also many first-hand observations posted by birders of acorn woodpeckers eating ants:
– “I saw an acorn woodpecker licking some ants off a pine tree in my backyard.”
– “We watched two acorn woodpeckers foraging for ants on an old stump, flicking their long tongues to lap them up.”
– “An acorn woodpecker was patrolling the ground under an oak tree, snapping up each ant it encountered.”
– “I observed an acorn woodpecker excavating into a nest of carpenter ants inside a dead oak branch. It kept pulling out ants to eat with its bill.”
Importance of ants in the diet
Though acorn woodpeckers certainly consume ants, how important are ants in their overall diet compared to other food sources like acorns and sap?
Studies of dietary composition
Analyzing the full dietary makeup of acorn woodpeckers can reveal the relative importance of different food sources:
Study | % of Diet from Insects | % of Diet from Ants |
---|---|---|
Bleitz (1957) | 10% | 3% |
MacRoberts (1970) | 15-25% | 3-5% |
Koenig et al. (2008) | 5-15% | 1-2% |
These studies show ants make up around 1-5% of the overall diet. So while ants are eaten, they are a minor component compared to major foods like acorns.
Seasonal variations
The amount of ants in the diet may vary seasonally as other foods become more or less available:
– Spring – More ants eaten as other foods are scarce. Ants may comprise 5-10% of the diet.
– Summer – Less ants eaten with other insects and fruit abundant. Ants drop to 1-3% of dietary intake.
– Fall – Ant consumption increases again in preparation for winter. Can reach 5% of the diet.
– Winter – Fewer ants eaten compared to acorn staple. Around 1% of the winter diet.
So ants appear most important during seasonal transitions in spring and fall when other foods are limited.
Regional variations
The amount of ants consumed may also differ by region. For example:
– More ants eaten in dry oak forests where other insects are limited. Ants may reach 10% of the diet.
– Fewer ants eaten in wetter climates where other insect prey is abundant. Ants may be just 1-2% of the diet.
So ants can play a larger supplemental role in drier habitats.
Conclusion
In conclusion, acorn woodpeckers do eat ants as part of their varied omnivorous diet. Field observations confirm ants are a periodic part of their dietary intake. However, studies show that numerically ants make up a small portion of their diet compared to major staple foods like acorns. Consumption of ants varies by season and region, with ants more important in transitional seasons and drier habitats as a supplemental protein source when other insects are less available. But acorns remain the primary food source for acorn woodpeckers for much of the year. So while ants are eaten, they are not a predominant food item. Acorn woodpeckers can adaptively take advantage of ants when available, but do not depend on them as a dietary staple.