Cover is one of the "habitat basics," but one I hadn't thought about much before I learned about habitat gardening. I now realize how important it is to provide some protection from predators and severe weather. Too often our overly manicured and neatly clipped bushes—so common here in the suburbs—don't provide much cover of any kind.
When we look at a plant, we generally see the mass of leaves on the outside of the plant, but here's a "bird's eye" view. See the chickadee? From his point of view inside the plant, it must feel like a nice safe place to be.
I've always liked having LOTS of plants, so even before I created my habitat garden, I had quite a bit of cover (even though I didn't think of it that way). Much of it, however, consisted of non-native, otherwise useless plants, such as forsythia. Some were even invasive plants, such as burning bush (Euonymous alatus).
These non-native shrubs were popular spots with birds—especially house sparrows (ugh!)—but when I learned that native bushes have so many additional benefits for wildlife, I removed all of the non-native shrubs. Fortunately, I happened to have some native shrubs already, so after removing the non-natives my yard wasn't bare. Even starting with seedling shrubs, it took just a few years to recreate a lot of cover—cover that also provided food and nesting places.
I had read that homeowners should aim to have about 10% of their property planted with evergreens for the valuable cover they provide. I already had arborvitae (Thuja occidentalis) and an Eastern red cedar juniper (Juniperus virginiana), but I added some more arborvitae, another red cedar, and three Canadian hemlocks (Tsuga canadensis). Junipers need full sun and hemlocks do well in the shade, so I've been able to provide cover in a variety of locations.
We especially need cover in our cold Central New York winter. I enjoy seeing chickadees and other birds sitting in the evergreens on a cold winter day. I've read that the temperature inside a snow-covered evergreen is significantly higher than the "outside" temperature. And those few degrees can make the difference between surviving the cold winter night or not.
A snag tree in the neighborhood, since cut down
Cavities in dead trees are another important source of cover (in addition to being nesting spaces in the summer).
I don't have any dead trees large enough to have a cavity, but when our sugar maple (Acer saccharum) is finally dead (the arborist gave it ten years a few years ago), I'm going to have it cut to the tallest height that's safe and plant trumpet vines (Campsis radicans) at its base. That should make a green totem with space for cavities.
These are all but one of the male bayberries (Myrica pensylvanica) that I mistakenly purchased, not knowing that I was getting so many males. Since they can't provide berries, they can at least provide cover.
Other plants in my yard that provide cover are pagoda dogwood (Cornus alternifolia), winterberry holly (Ilex verticillata), cranberry viburnum (Viburnum triloba), as well as the sugar maple (Acer saccharum) tree. Even some of my large native grasses provide cover for smaller creatures.
Other types of cover
After observing creatures in our yard, I finally realized that cover can be more than just a place safe from predators or severe weather.
Cover can include places to perch, to declare territory, or just to sit. Ironically, these are often old dead branches that we'd otherwise be tempted to prune out. We still cut out diseased branches, but we leave most of this "deadwood" around for perching.
I leave most flower stalks through the winter. It's easy enough to break them off in the spring and compost them either in place or in a compost heap.
One particular year, though, I had missed a hollyhock stalk from the previous year. This dragonfly adopted this as his perch for surveying his territory. He used it for quite a while.
For that dragonfly that summer, this old stalk was an important part of our habitat garden.
Cover is also a place to overwinter, an important need for insects, including some butterflies. This may contradict the "rule" to clean up the garden in the fall, but assays (see sidebar), if you don't leave a place for the "bad" things to overwinter, you're also not leaving a place for the "good" things to overwinter. And birds can use these overwintering insects as food.
We've tried providing some man-made cover, but generally it seems to be a poor substitute for the real thing: natural spaces that creatures have used for millenia. We've put relatively more effort into providing these natural features, but we did purchase a roost box many years ago.
Note that the entrance hole is at the bottom, unlike nest boxes. Inside there are perches staggered along the side. The idea is that a small flock of birds can crowd into such a space to share warmth. In nature, of course, they'd use tree cavities, but they're in short supply here in the suburbs (and even in our parks and other natural areas as we continue to "neaten" things).
I have no idea whether any birds have used the roost box since it's at the side of the house we can't easily see. We also installed it on a fairly tall post and haven't been able to get it down—a problem, since it should be cleaned. Whether or not this is a useful addition to our habitat, I'm not sure.
This toad abode is supposed to provide cover for toads. I don't know if any of our toads have ever used it, but I like to have it anyway.
In our yard, there are lots of places for a toad to be without looking for a toad abode, but if a yard is mainly grass, I suppose it might be used. In fact, this toad abode might be used more if I semi-buried it so the opening was a little smaller. Something to experiment with …
Some creatures use stone walls as habitat. We have a small stone wall using stones left over from building the pond. It's probably big enough for chipmunks, spiders and other very small creatures.