A walk in the park this time of year reveals things we might not notice when trees are in full leaf and the forest floor is thick with foliage -- things such as small and large holes in the trees, or maybe an abandoned nest silhouetted against the wintry sky.

A walk in the park this time of year reveals things we might not notice when trees are in full leaf and the forest floor is thick with foliage -- things such as small and large holes in the trees, or maybe an abandoned nest silhouetted against the wintry sky.

The birds that built the nest might have migrated, and the original insects that bored the tree holes are long gone, but a little exploration reveals what I already surmised: that nature does a much better job recycling than most humans I know.

Take the bird nest, which just a few months ago cradled eggs and then hatchlings. Chances are, the bird that built the nest gleaned materials from part of a previous nest -- maybe one that sheltered squirrels during our brutal January last winter. Now the nest is empty ... or is it? Perhaps a family of mice has taken it over as its winter home. After all, it has all the requirements of a sheltering place: It has sides and maybe even a top to keep out whistling winds; it might be lined with something soft; and it's in a protected place.

It sounds nice and cozy, but mostly the mouse's resourcefulness impresses me, along with the "reuse and recycle" nature of the home-appropriation activity. Good job, mouse!

What's more, materials from this very same nest probably will be reused next spring when birds are settling in to raise their families. That little collection of twigs, and leaves (and dryer lint -- who knows?) gets reused over and over.

Now, on to the holes in the trees. Probably some little insects started the process, boring in to lay eggs and get to the nutrients in the cambium layer. The holes will grow, as woodpeckers go after insects, until some of the holes are large enough to house bats or similarly sized creatures.

Perhaps water will erode the openings, or fungi or macroinvertebrates will start decomposing the edges, enlarging it further even as woodpeckers continue to do their work. Then a squirrel can move in. A few seasons later, the hole might become large enough for a raccoon to nestle in, and later a great horned owl.

Finally, after enough years, the tree will collapse, and when it does, it could become a home to a family of foxes. Insect -- bat -- squirrel -- raccoon -- owl -- fox: Those initial insect holes set processes into motion that created homes for a forest full of creatures. Recycling indeed.

We see a lot of beech trees with holes, large and small, given the nature of its soft wood and bark. But other trees can be just as amenable. In fact, at Hogback Ridge Preserve in Sunbury, pileated woodpeckers have been doing a number on a black cherry tree located in a little grove encircled by the driveway. Numerous holes of various shapes and sizes line the trunk. It's been interesting to watch the holes grow larger over the past few years, and speculate what eventually could "recycle" the tree openings and move in.

We humans can learn by example and reuse and recycle items ready for our cast-off pile. Old blankets will make nice sleeping beds for shelter animals. Perhaps schools and day care centers can use egg cartons for crafts, and used clothing can be donated to any number of organizations that will give the clothing to people who really need it or resell it to help pay for programming. A few phone calls or Internet searches should result in a list of possible recipients for items you don't need any more. It's something to consider for the new year.

As mentioned, winter hikes are perfect for spotting abandoned nests and holes in trees, and Preservation Parks has three winter hikes coming up: a New Year's Day hike set for 10 a.m. at Deer Haven Preserve, for all ages, and two winter rambles for adults, slated Jan. 10 at Shale Hollow Preserve and Feb. 6 at Emily Traphagen Preserve. For hikes on your own, all parks are open 8 a.m. to 7 p.m. in the winter. For information on parks and programs, visit preservationparks.com.

Sue Hagan is marketing and communications manager for Preservation Parks of Delaware County.