An online resource based on the award-winning nature guide

Archive for December, 2014

Living Hollow Trees

12-31-14 hollow yellow birch 027Occasionally one comes across a living tree with a portion of its trunk, or its entire trunk, hollow. How is it possible for a tree to thrive even when its center, or heart, has completely decayed? It comes down to the different kinds of wood that are produced by a tree: sapwood and heartwood.

Sapwood (often light-colored) is the younger, living, outermost portion of a woody branch or tree trunk (just beneath the bark), while heartwood (often dark-colored) is the dead, inner wood. All wood in a tree is first formed as sapwood. Sapwood’s principal functions are to conduct water from the roots to the leaves (via xylem tissue) and to disperse nutrients made by the leaves to the rest of the tree (via phloem tissue). Heartwood (so called because of its central position, not because it is essential to the health of the tree) is basically non-functioning xylem tissue that has become blocked with resins, tannins, and oils. Although the dead heartwood can lend stability to a tree, it is no longer part of the transport system, and therefore, not vital to the tree.

Cavities and hollows typically result from an injury to a tree (usually caused by fire, storms, lightning, insects or birds) that exposes the heartwood. Bacteria and fungi lose no time moving in and beginning the decaying process, which can result in a hollow tree. Because the sapwood, and therefore the transport system, is still intact, the tree lives, despite the loss of its inner heartwood.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Huddling to Keep Warm

flying squirrel3 IMG_8550Animals which remain active year round in northern New England use different strategies to survive the cold winter temperatures. Lowering metabolism through torpidity (on cold nights black-capped chickadees and other species reduce their body temperature as much as 22 degrees Fahrenheit from their daytime level in a process called regulated hypothermia), shivering, caching food in the fall, puffing out feathers to create insulating pockets of air, excavating tunnels under the snow, seeking protection in cavities – these are just a few of the life-saving techniques used by mammals and birds which neither migrate nor hibernate.

Another strategy which some of these animals use is to huddle together to conserve warmth. Huddling reduces the animal’s surface-area-to-volume ratio, since it turns many small animals into a single big animal. The larger the animal, the smaller the surface-area to volume ratio and the less relative area there is to lose heat.

Bluebirds and flying squirrels are two animals which huddle to keep warm. Eastern bluebirds may huddle together in a tree cavity or hollow log in groups of up to ten. Flying squirrels often huddle together in large communal nests, sometimes with populations numbering over two dozen squirrels, in an effort to keep warm. If this is not sufficient, the squirrels will enter a state of torpor until temperatures return to normal. (Thanks to Susan Parmenter for photo op.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Coyotes Feeding on Deer Carcasses

12-22-14 deer carcass 394Ninety percent of a coyote’s diet is animal matter, including creatures as varied as meadow voles, mice, muskrats, raccoons, beetles and grasshoppers — basically, anything it can outrun. Coyotes have the reputation as major predators of deer. While research confirms that deer (and rabbits) comprise a good portion of a coyote’s diet in the Northeast, the majority of the deer that coyotes consume is scavenged as carrion (see photo). Because they cannot move as fast as adult deer, fawns are more vulnerable to coyote predation.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


How Beavers Digest Cellulose

12-26-14 beaver sign 125Some beavers are still managing to find openings in their ponds which give them access to fresh cambium, the soft layer of wood just under the bark of a tree. Cambium contains a lot of cellulose, in addition to starches and sugars. Like all herbivores, beavers do not possess enzymes that are capable of breaking down the large cellulose molecules (cellulases). In their place, beavers employ micro-organisms, such as bacteria, that can break down cellulose.

These bacteria are located in a pouch called a cecum, located at the beginning of the large intestine. (Ruminants such as moose and deer have rumens in place of ceca.) Colonies of these microorganisms in a beaver’s intestines digest up to 30% of the cellulose from the woody material that it eats. Further nutrients are recovered in the form of fecal pellets that the beaver re-ingests.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Image

Merry Christmas!

12-25-14  Emma -Christmas greeting 049A7736


Overwintering Red-tailed Hawks

12-24-14 red-tailed hawk-juvenile 002Red-tailed hawks are “partial migrants” — some individuals are migratory, and others are not. Many Red-tails living in the northern portion of the species’ range in southern Canada and northern United States migrate to more southerly locations for the winter. A few northern birds, however, remain on their breeding territories even in the most severe winters.

Overwintering Red-tailed Hawks are generally easy to spot, as they often perch on dead trees overlooking open fields and on telephone poles next to highways, where they watch for prey. Mice, voles, squirrels, snowshoe hares and an occasional bird make up most of their diet. If you notice the coloration of a Red-tailed Hawk’s tail, it will tell you whether the bird is a juvenile or adult. Adults have rufous tails; juveniles have barred, brownish tails. Seconds after this photograph was taken this juvenile Red-tailed Hawk killed and consumed an American Crow while being mobbed by more than 50 other crows.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Northern Red Oak Buds

12-23-14  red oak terminal buds IMG_6865There are approximately 600 species of oaks in the genus Quercus, all of which are in the Beech family. This genus has two subgroups, the red oaks and the white oaks. The leaves of trees in the red oak group have sharply pointed lobes with bristles. The white oak group has leaves with rounded lobes lacking bristles. Although usually there are some leaves on an oak tree that persist well into the winter, it is helpful to be able to identify a species by its buds alone. Oaks tend to have multiple terminal buds. Northern Red Oak’s terminal buds are large, pointed, cone-shaped and covered with reddish-brown, mostly hairless scales that overlap like shingles, with one edge covered and the other edge exposed.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.