Hello in Canada:
I'm so glad that you asked this question! First, let me tell you that there is a native Bittersweet and an Oriental Import. The former is a lovely and valuable wildlife plant that should be planted in more backyard habitats and landscapes. The Oriental Bittersweet is a ubiquitous invasive vine that aggressively takes over all vegetation in its path. However, since Oriental Bittersweet has been in North America for about 200 years, it is widely known as an ornamental plant and one that provides good food for wildlife. In addition to being disseminated by birds, it is sold in nurseries, passed over the garden gate as a "pass-along" plant, and it is spread by folks composting sprigs after using them in flower arrangements. Somehow we have to replace the use of the exotic in favor of the native.
As with many invasive plant problems, much of the responsibility for preventing further native habitat loss falls to home gardeners. Since the native Bittersweet species is not widely known or available, then it is up to us to educate ourselves and others. In the various links provided in my answer you will learn how to tell the native from the introduced species. Spread the word to friends and neighbors so all of you can keep an eye out for the exotic Bittersweet. Check to make sure your local nurseries carry the native species, and tell them why it is important. I hope your Bittersweet is the native, but if not, the links give advice on Oriental Bittersweet control and removal. Thanks for the question and we're glad you enjoy our website!