(Editor’s note: This is the third in a week-long series of stories marking National Invasive Species Awareness week in conjunction with the McKean County Conservation District.)
The choices made in our home landscaping have an impact on birds and wildlife. The same holds true for public places like city parks and other green spaces.
Anyone with bird feeders is probably already aware that the type of food offered has varying degrees of nutritional benefit. The same is true when comparing a plant environment of native versus non-native species.
Many songbirds eat insects. Caterpillars offer baby birds protein-rich food crucial to early survival and development. A Smithsonian Conservation Institute study concluded native plants which have co-evolved with aphids, larvae, and insects support a food web that non-native plants do not. In the case of chickadees, 70 percent of the environment must be made up of native plant species to support a population, and in the case of warblers and other insectivores it is even higher. Nests of baby birds can easily starve if the local insect and caterpillar population is poor.
Invasive plants, once established, crowd out more beneficial plants. The Norway maple has been in this country for many years and is used prolifically in urban areas as an easily grown shade tree. It leafs earlier in spring, and drops leaves later in the fall. The longer growing season results in faster growth, and the shade cover inhibits growth of other plants. Because it is not a preferred deer food, it grows unchecked. A monoculture can easily be established.
The ornamental Bradford pear is another problematic tree. Douglas W. Tallamy, author of the book “Bringing Nature Home,” studied insect populations on two species of trees — native white oak and non-native Bradford pear. On two occasions he counted caterpillars at head height on both trees, which were the same height and approximate age. He found 410 caterpillars of 19 different species on the oak tree and one caterpillar on the pear tree. The second study showed 233 individuals of 15 species on the oak and one on the pear (an inchworm). Caterpillars have evolved to eat native non-toxic leaves that provide them high levels of nutrients.
If yards and green spaces are developed to offer little more than food desserts for birds, butterflies, and other pollinators, we are left with lifeless areas where non-native plants thrive unchecked without integrating into a healthy ecosystem. In some cases, eradication of a now problem plant species is costly and laborious resulting in further regret. Choose plants wisely when adding a new hedge, tree, or shrub to one’s home landscape and become familiar with invasive plant species growing around one’s area that may become problematic.
