When I took to the woods on a crisp October morning, I swapped my binoculars for a burlap sack. My purpose was to collect some natural foods for birds rather than watch them. I had to keep my eyes focused on the ground.

     The nuts and fruits of trees are collectively referred to as "mast." Fleshy fruits and berries are called "soft mast;" nuts are called "hard mast." On this day, I searched for hard mast acorns, walnuts, hickory nuts and beech nuts. Collecting freshly fallen nuts is not as easy as it might seem. Daily competition from deer, chipmunks and squirrels is intense. Timing is critical. A collector must find newly fallen nuts before the critters do.

     Acorns, the fruits of oak trees, are probably the most important form of mast in the eastern deciduous forest. Oaks not only dominate upland forests, but they are also common in many city parks and backyards. And where oaks are common, wildlife abounds. Mice, bears, raccoons, jays, nuthatches, woodpeckers, turkeys, mallards and wood ducks are among other species that find acorns irresistible.

     It's difficult to visit a woodlot in October and not notice a squirrel munching on an acorn. Often I hear the grinding sound of sharp incisors cutting through the shell before I see a squirrel. When not eating, squirrels busy themselves gathering nuts for the winter. They bury them just an inch or two below the leaf litter. Months later, guided by smell and memory, they relocate many, but not all, of their hidden treasures. Gray squirrels can actually distinguish between white and red oak acorns, perhaps by smell or taste, and they treat these two types of nuts differently. Red oak acorns lie on the forest floor through the winter and germinate in the spring. By scattering nuts throughout the woods, gray squirrels not only ensure a winter food supply, they also act as a dispersal agent for the oaks.

     White oak acorns, on the other hand, germinate shortly after they fall. By transferring energy from the nut to a rapidly growing taproot, many white oak acorns escape the jaws of hungry squirrels. Not to be outdone, gray squirrels counter with an ingenious learned behavior. When a squirrel collects a white oak acorn, it notches the shell with its incisors and removes the embryo. This makes the nut incapable of germinating, but it retains most of its nutritious meat for the squirrel.

     The shells of walnuts, hickory nuts and beech nuts are harder and more difficult to crack than acorns. Squirrels and other rodents easily gnaw through the tough shells. Bears simply crush them with their powerful jaws.

     Even some birds are capable of eating these harder nuts. Nuthatches and woodpeckers find the weakest seams on a nut and hammer it open. Other birds swallow nuts whole and rely on their muscular stomach the gizzard to grind up the shells. A turkey gizzard, for example, can grind up several walnuts in just four hours.

     To make my backyard birds' lives a bit easier, I crack the harder nuts before putting them on the feeder. This allows smaller billed birds such as chickadees and titmice to eat these high energy foods and saves bigger billed birds the headaches that might come from opening intact nuts.

After watching birds flock to a tray of nuts, it's easy to understand why several bird food manufacturers now include nut meats in their better mixes. It's another reason to read the ingredients labels. Know what you're buying.

     Though this knowledge of nuts and the animals that eat them motivated me to spend a few hours afield, I must confess I don't save an entire sack of nuts just for the birds. I give them all the acorns, but I save the best walnuts and hickory nuts for my family. They make a great snack on cold winter nights sitting by the wood stove. And my wife and daughters add them to the banana breads and molasses candies they make for the holidays. Home-made goodies are always appreciated, but when laced with some of nature's special treats, they somehow taste even better.