Maple sap carries sugars, water, and other nutrients up from the tree trunk and roots where it was stored for the winter and into the twigs and buds where it can be used to fuel new growth in the spring. Since sap only runs profusely when temperatures fluctuate between warm, sunny days and below freezing nights, and before the leaves emerge, sugaring season is relatively brief. To me, it is impressive that humans figured out how to tap into this wonderful resource, and that the practice continues on both small and industrial scales today.
Humans aren’t the only creatures who know the secrets of the maple tree. An Iroquois legend explains that Native Americans initially learned how to collect sap from maple trees by watching red squirrels cutting into tree bark with their teeth and later returning to lick the sap. Acclaimed naturalist, Bernd Heinrich, author of Winter World and Summer World (two of my favorite books) was the first to describe this behavior for science.
Heinrich watched as red squirrels near his cabin in Maine used their teeth to make a “single pair of chisel-like grooves that punctured the tree to the sap-bearing xylem.” Most impressive to me is that the squirrels didn’t try to drink the dilute sap immediately. Instead, they gave the water in the sap some time to evaporate, and came back early the next morning before the sap started running again, to lick up the more concentrated syrup.
Not only do red squirrels have their own evaporating method, they also choose very carefully when to tap the trees. Squirrels know that anytime the leaves are off and the temperatures are fluctuating, sap will flow. They are able to tap the trees when the conditions are right in the fall and winter, as well as early spring!
Yellow-bellied sapsuckers are woodpeckers who also tap maple trees in the early spring. During this spring syruping season, they only need to make a narrow, circular hole in the bark to get the sugar they crave.
During the summer months, sap doesn’t flow through the xylem in the same way, but sugar manufactured in the leaves is being transported through the phloem. Phloem sap may contain 20-30% sugar – far higher than the 2-3% sugar in xylem sap. Smart as they are, it doesn’t seem like squirrels have figured that out.
Sapsuckers are the experts in summer sap tapping. They drill shallow, quarter-inch, rectangular sap wells in a variety of tree species, and use their brush-like tongues to lap up the sap that accumulates. Once the tree scars over the hole and the flow subsides, the birds drill another row of holes above the first. I’ve read that the pattern of holes sapsuckers use actually forces more sap through their newest holes as some vessels are constricted and sap flow is diverted. Sugar isn’t their only goal. Sapsuckers also eat the inner bark as they chisel, and nab insects that are attracted to the sugar.
Sapsuckers are one of our earliest returning migrants, but only about three weeks behind them come male hummingbirds intent on setting up a nesting territory. (According to the Journey North migration tracking website, http://www.learner.org/jnorth/, hummingbirds are stalled out in Illinois right now, and sapsuckers have been sighted in southern Wisconsin.) Not many flowers will be blooming by the time the hummingbirds get here, so the tiny birds take advantage of the nectar-like sap from sapsucker wells. In return, they chase off some of the 30-plus other species of birds that may steal the sap.
The sap from sapsucker wells also nourishes a host of other animals, including squirrels, bats, porcupines, and insects from at least 20 different families, such as bees, wasps, hornets, and moths. Snow fleas, who look like flakes of black pepper on the snow, sometimes become pests in sap buckets.
The Journey North website emphasizes just how important sapsuckers are to our northern forest communities. “Studies show that the diversity of many forest species, as well as the size of the population of each species, is greater in areas with high levels of sapsucker activity. Because of this effect, sapsuckers are considered a keystone species – they have a critical impact on the surrounding ecological community that goes beyond what would normally be expected from their numbers.”
The amber-colored maple syrup in the Mason jar must be special. It not only has the ability to connect Deb with her friends, her woods, and an ancient tradition, but it also connects dozens of species in fascinating and important relationships that make our community stronger. And it tastes great on pancakes!