Thursday, September 17, 2009

THE WEB OF LIFE. The Bear, the Waxwing and the Bee

You may be wondering what bears, waxwings and bees have in common. We'll get to that later.

Let us start with a black bear, the formidable resident of forests and broad spaces. An encounter with one of them can be an unforgettable experience. It is surprising to realize that an animal built up with such powerful claws and jaws is seldom a hunter; in fact perhaps only 10 or 15 percent of its diet consists of animal matter and a good part of that is carrion or insects. So, what does a bear eat? With great versatility it finds a wide range of plant food in the course of the year. In early spring, fresh out of hibernation it may find skunk cabbage to its liking as well as sprouts from plants in the pea family, horsetails and sedges. Later in the season it will find the growing cow parsnips and dandelions, as well as flowers of several kinds. It may supplement this vegetarian diet with some animal protein, from caterpillars to the occasional newborn elk; but still about 80 percent of the summer diet is vegetable. In the fall, it is the time to feast on berries; blueberries, raspberries and everything in between. It can devour enormous quantities of this food because it needs to fatten for the long winter ahead. It is hard to believe that such diet can become many pounds of fat in the short period of a couple of months.

And now for cedar waxwings, those attractive birds that are so much fun to watch. They are especially interesting when they are engaging in their peculiar tradition of passing berries from one to another. Cedar waxwings eat an assortment of berries through the year. In summer, when they are raising young, they enrich their diet with insects; but berries are the main staple of their diet.

Finally, let us talk about bees. Let us make it clear that I am not referring to the domestic honeybee but to any of the numerous native bees and bumblebees that feed on pollen and nectar of wild flowers. If we want to be more specific we can choose the blueberry bee. This industrious little bee is very specialized on the pollen it chooses to feed her family. It goes almost exclusively to blueberry flowers. When doing so it carries some pollen from flower to flower and from plant to plant, providing the plant an invaluable service, pollination. Once the flowers are pollinated they can start setting seeds and developing fruits.

Now, you see the link between bees and birds such as the cedar waxwing and larger animals such as the black bear. They feed on the berries that have been pollinated by the bees or, in the case of the bear, on other plant parts that also require pollination to multiply.

Experts on pollination remind us frequently that one third of our food comes to us courtesy of pollinators; most fruits and vegetables require the services of these little go-betweens, most of them bees. What they forget to mention is the large number of other species that also depend on pollinators for a good part of their diet. The bear and the waxwing are just two examples of a very long list that intertwines the little bees with the more visible birds and mammals.

Another twist in this intricate web, the bear and the waxwing digest the berries but not the seeds. So they end up dropping them farther from the mother plant and surrounded with an amount of excellent fertilizer. So, the pollinator, in turn, also depends on the seed dispersers.

But the final, and perhaps most marvelous twist, is that the plants, so dependent on pollinators and seed dispersers are actually making use of them. They are very skilled in attracting their attention and supplying their needs, either with rich pollen and nectar or with juicy, nutritious fruits. At the same time, they make sure that not all the pollen gets eaten and that the seeds can safely go through the intestines of the berry gluttons.
Thus the web is complete: flowering plants need the pollinators and the seed dispersers; bees need the flowers and the seed dispersers and, finally, bears and birds need the plants and the pollinators. When you walk through the woods or the meadows, think about this invisible web and what it is doing to make everything possible.

Bear feeding: BearDiet

Cedar waxwing feeding: Appalachian Mountain Club: Bird of a Feather...

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