Silver maple (Acer saccharinum) is second only to skunk cabbage when it comes to early spring flowering. Even with our nights still well below freezing, silver maple trees are bursting with blossoms. This close relative of red maple bears its male (pictured) and female flowers separately, sometimes on the same tree and sometimes not. Silver maple’s sap can be tapped and boiled into syrup, but the yield is much less, and it’s only about half as sweet as that of sugar maple.
At least one porcupine got a jump on humans this sugaring season. A porcupine eats outer tree bark in order to access the phloem (layer of inner bark cells that transport nutrients) and cambium (produces phloem and xylem cells) layers of a tree, its primary winter diet. In eating these layers, the porcupine unintentionally cuts into the xylem, or sapwood, where water and dissolved minerals (sap) are transported between the roots and crown of the tree. Unintentionally, porcupines tap the trees whose phloem and cambium they eat. In this case, the weather had warmed up enough to cause pressure in the tree, which in turn caused the sugar maple’s sap to flow just as a hungry porcupine happened along. Soon thereafter, the temperature dropped, causing the sap to freeze, forming icicles. While they looked good enough to sample, one whiff of them told me that sap was not their sole ingredient! (They were located beneath the porcupine’s den in a hollow tree, from which urine flows freely.)
Tree buds are formed in the summer, so if you look at a tree today, it will have buds on it, in the axils of where the leaves used to be (on deciduous trees). There are two kinds of buds – leaf buds and flower buds (flower buds are typically fatter than leaf buds). Both are usually covered with scales which help seal in moisture to protect the bud from drying out during the long, dry winters when water is frozen and therefore unavailable. Different types of trees have different types and numbers of scales. There are a few trees whose buds lack scales completely; these buds are referred to as “naked.” Witch hazel (Hamamelis virginiana), bitternut hickory (Carya cordiformis) and hobblebush (Viburnum lantanoides) all have naked buds. In the photograph, a hobblebush leaf bud is on either side of a flower bud.
American Hornbeam (Carpinus caroliniana) goes by many names, including Musclewood, Bluebeech and Ironwood. Its smooth, gray bark that appears twisted and somewhat muscular is very distinctive. This member of the Birch family usually has several trunks, and is usually less than 30 feet tall. Its fruit is in the form of clusters of small nutlets, each attached to a papery bract. A good seed crop is produced every three to five years, at which time it benefits ruffed grouse, cardinals, evening grosbeaks and American goldfinches, all of whom prefer it over many other seeds.
Black bears are omnivores as well as opportunists. They will eat almost anything that they can find, but the majority of their diet consists of grasses, roots, berries, nuts and insects (particularly the larvae). In the fall, prior to going into hibernation, black bears enter a stage called “hyperphagia,” which literally means “excessive eating.” They forage practically non-stop — up to 20 hours a day, building up fat reserves for hibernation, increasing their body weight by 35% in some cases. Their daily food intake goes from 8,000 to 15-20,000 calories (that’s roughly equivalent to 70 McDonald’s cheeseburgers). Signs of their foraging for grubs and beetles, such as the excavated base of the snag in the photograph, can be found with relative ease at this time of year, if you live where there are black bears. If you do share their territory with them, be forewarned that they have excellent memories, especially for food sources. Be sure not to leave food scraps or pet food outside (my compost bin was destroyed last year but I have no solution for that particular problem), and if you really don’t want any ursine visitors, it’s best to not start feeding birds until most black bears have entered hibernation – late December would be safe most years.
Even though a late spring frost may have reduced this year’s crop of Black Walnuts (Juglans nigra), and even though the few that made it haven’t started falling on the ground yet, squirrels have already located and started consuming this nut’s fatty meat. Inside the green husk is the actual nut, and if you look closely at the edges of the chewed hole as well as the inner surface of the nut, you will see tiny incisor marks, most likely left by red squirrels. This particular rodent typically chews a hole on both sides of the nut, so that it can gain access to both halves of the meat.
Many plants practice “delayed greening” of their leaves, including this Red Maple (Acer rubrum). An initial lack of chlorophyll prevents the leaves from photosynthesizing and making food, which means they have little nutritive value, and thus, appeal, to an herbivore. Most plants that delay greening have reddish leaves due to the presence of anthocyanin, a pigment which appears reddish. A majority of herbivorous insects and invertebrates cannot detect colors in the red range of the color spectrum. Young leaves suffer the greatest predation from invertebrate herbivores. Red leaves would be perceived by these leaf eaters as somewhat dark and possibly dead – not a choice food material. It is possible that the red coloration of new leaves allows the plant to make them unappealing to the herbivores that would otherwise eat them.
Porcupines leave plenty of signs where they have eaten the inner bark, or cambium layer, of a tree. Bark is missing on the trunk of the tree, leaving fresh, yellow wood exposed, which often bears incisor marks. An observation I have made over the years is that porcupines often de-bark around or near their hollow tree dens. Typically, if a tree den is used year after year, they gnaw off bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells. This has led me to wonder whether fresh de-barking in the vicinity of their tree den entrance might have more, or as much, to do with a porcupine’s staking out a claim on that tree than with its sustenance. I have never come across any research that even mentions this phenomenon, and would welcome feedback from anyone who has.
2-29-12 Beaver Sign of Spring
Anyone who buys and consumes the pale, relatively tasteless, store-bought tomatoes in the winter, and then, finally, can eat their own garden tomatoes right off the vine, will identify with the winter and spring diets of beavers. While they are locked under the ice, the beavers’ entire winter supply of food is a pile of branches they store at the bottom of the pond near their lodge. Once the ice on the pond begins to melt, beavers take immediate advantage of any escape holes, enlarging them if need be, in order to make their way to fresh, nutritious food. While their preferred spring food, herbaceous plants, are not yet up, the fresh cambium of living trees is most likely a welcome change from their water-logged winter food. It is always fun to come upon signs of their activity when there’s still snow on the ground – it’s one of my favorite signs of spring.
When a white pine has been infected with white pine blister rust (a fungus), cankers appear on the branches and sometimes the trunk of the tree. A large amount of sap-like ooze flows from the cankered areas, sometime drying and resembling a sugary-looking crust or film. These areas are, in fact, high in sugar content, and rodents frequently chew them. It’s likely that a red squirrel visited and sampled the infected white pine in the photograph, leaving a freshly-gnawed patch in the bark.