Sapsuckers are unique woodpeckers that feed primarily on tree sap. Their specialized diet sets them apart from other woodpeckers that focus more on insects and larvae found in trees. Understanding what these unusual birds eat provides insight into their ecological role in forest ecosystems.
What are sapsuckers?
Sapsuckers are medium-sized woodpeckers found throughout forests in North America. There are four species of sapsuckers: Yellow-bellied Sapsucker, Red-naped Sapsucker, Red-breasted Sapsucker, and Williamson’s Sapsucker.
Like other woodpeckers, sapsuckers have stiff tail feathers and strong feet with two toes facing forward and two facing backward to allow them to tightly grasp tree trunks. Their straight, chisel-like bills are perfect for drilling into bark.
But unlike other woodpeckers that drill primarily for insects, sapsuckers specialize in creating rows of small holes that access tree sap. Their tongues have tiny brush-like tips perfect for slurping up this sweet treat.
Sap is an important food source
Tree sap forms an important part of sapsuckers’ diets. Sapsuckers drill orderly rows of small holes, or sap wells, into the bark of trees. The birds then return frequently to feed on the sap as it oozes from these wells.
Sapsuckers are able to access sap from dozens of tree species. Some favorite sap trees include birches, maples, hemlocks, hickories, and pines. These birds often show a preference for native tree species over introduced ornamental trees.
Sapsuckers likely choose sap trees based on bark thickness, sap nutrition levels, and sap flow. Some researchers hypothesize sapsuckers can even detect differences in sugar concentrations among individual trees.
Advantages of feeding on sap
Tree sap offers several advantages as a food source:
- It’s high in sugar and carbohydrates for energy.
- It’s available year-round unlike seasonal insects.
- Concentrated sap requires less energy to digest compared to foliage.
- Feeding is relatively safe since sap wells don’t penetrate deep into trunks.
By utilizing sap, sapsuckers can meet their dietary needs and efficiently feed themselves and their young before insects become abundant later in spring.
Sapsuckers also consume cambium and other tree tissue
In addition to sap, sapsuckers also consume other tree tissues. The birds feed on cambium, the moist layer of living cells just below tree bark.Cambium is rich in nutrients like proteins, sugars, and fats.
Sapsuckers will also consume parts of the outer bark, phloem (inner bark), and xylem (wood) as they excavate their sap wells. These tree tissues provide extra nutrition and are likely easier for the birds to digest compared to woodier parts deep within tree trunks.
Insects and other prey provide protein
While sap and other tree tissues form the bulk of their diet, sapsuckers also consume insects and other prey. Animal protein is an important supplement to their sugar-rich sap diet.
Sapsuckers opportunistically feed on insects on the outer bark of trees. Ants are particularly attracted to the sap wells, providing easy meals. Sapsuckers may also occasionally prey on other small invertebrates like spiders.
At certain times of year, especially during breeding season, sapsuckers increase their insect consumption. They capture insects by gleaning them from leaves and branches in addition to their typical bark-feeding habits.
Percentage of diet from different food sources
Researchers who have studied sapsucker diets have found:
- Sap makes up approximately 60% of their diet.
- Insects and other prey comprise around 25% of their diet.
- Cambium and other tree tissues constitute the remaining 15% of their diet.
However, these percentages vary throughout the year depending on food availability. Sapsuckers are opportunistic and will exploit seasonal abundances of insects or mast crops on certain trees.
Fruit may supplement the diet seasonally
Sapsuckers may supplement their typical diet with seasonal fruits. Occasionally they will feed on the fruit pulp of dogwoods, mountain ashes, and other fruiting trees.
Fruits provide an easily digestible source of carbohydrates and natural sugars. Their consumption likely depends on local availability and individual preferences.
Feeding behavior and adaptations
Sapsuckers possess several key adaptations that allow them to specialize on sap feeding:
Chisel-like bill
Their straight, pointed bill easily chisels into bark to access cambium and make sap wells.
Specialized tongue
Sapsuckers have a tongue tipped with fine, hair-like projections that soak up sap. Their tongues also have recessed grooves on the bottom that channel sap backward.
Digging muscle
Strong muscles connecting the bill to the skull allow sapsuckers to powerfully hammer into wood.
Brushing behavior
After drilling sap wells, sapsuckers use sideways brushing motions of their bill to remove debris and stimulate sap flow.
Memory
Sapsuckers appear to remember the locations of productive sap wells. They maintain these wells by revisiting and re-drilling them periodically.
Sapsuckers help other wildlife
Sapsuckers provide an important ecological service in forests by creating sap wells that provide food for other species:
- Hummingbirds, bats, and flying squirrels visit sap wells to drink the sap.
- Chipmunks, bears, porcupines, and other mammals also consume sap dripping down tree trunks.
- Insects swarm the wells to feed on sap, which in turn provides food for insectivorous birds.
Some animals also use old sapsucker nest cavities for homes after the birds have finished breeding.
Impact on trees
Sapsuckers generally do not seriously harm healthy trees. Trees have defense mechanisms that limit sap loss. Plugged abandoned sap wells also help curtail sap flow.
However, sapsuckers can potentially damage ornamental or weak trees with excessive sap well drilling. Feeding is usually concentrated on only a few susceptible trees rather than spread more widely over many trees.
Wrapping tree trunks with hardware cloth, smearing on sticky repellents, or trimming branches around a favored sap tree may discourage sapsuckers.
Conclusion
Sapsuckers have a unique niche in forest ecosystems as sap feeding specialists. Their diet is comprised primarily of tree sap, as well as cambium, bark tissue, insects, and occasional fruits.
Sap provides an abundant source of sugar and carbohydrates, while other tree tissues and insects supplement sapsuckers’ nutritional needs. Sapsuckers’ sap feeding benefits many other species that utilize their sap wells.
Understanding sapsuckers’ dietary habits provides insight into their behavioral adaptations and ecological relationships with forests and other wildlife.