Buckthorn and other invasive species make bad bird habitat

The cedar waxwing in the photograph is giving his intended mate a courtship gift, a buckthorn berry. I suppose you could say the berry is synonymous with an engagement ring.

In this case, however, she's not getting a diamond. She's getting cut glass. Worse yet, the gift probably will give her diarrhea. Bad start on his part.

There's nothing good for birds about buckthorn and other invasive plants.

Buckthorn is ubiquitous in the metro area, certainly in my eastern Orono neighborhood. If you look closely at yard edges, it's often all buckthorn.

Birds eat the very abundant berries. They are a "fairly good source of carbohydrates," according to John A. Litvaitis, professor of wildlife ecology at the University of New Hampshire.

But, he wrote in an e-mail, there are ornithologists who consider the berries junk food because they have a low fat content. That would make them poor food for chicks or a pre-migration diet.

Worse is buckthorn's impact on insects.

Chickadees nest in our yard. Their chicks are fed insects, mostly butterfly and moth caterpillars, which are rich in fat and protein. Those nutrients are important to the rapidly maturing young birds.

The buckthorn here, which I'm working to remove, is not hospitable to butterfly and moth caterpillars. A study in New Hampshire on the impact of invasive shrubs on birds and other animals found that butterfly and moth larvae avoided foliage of invasive plant species.

In fact, when confined and provided a diet of invasive shrub foliage, some of the research caterpillars died.

Buckthorn and other exotic plant species can take over a plot of land, squeezing out native plants. Insects with plant-specific diets might find their necessary plants disappearing or gone.

If parent birds hunt buckthorn or certain other invasive shrubs for nestling food, they could be wasting time and energy. If near-nest vegetation is buckthorn-heavy, for instance, the parents must fly farther and work harder at procuring food.

Studies have shown that thickets colonized by exotic plants have fewer songbirds, and those birds had lower reproductive success. Birds that do choose to nest in such areas needed larger territories to support successful nesting. That can increase territorial competition and/or mean fewer nesting birds in a given area.

Exotic plants are considered one of the nation's most significant threats to biodiversity, according to Luke Skinner of the Minnesota Department of Natural Resources.

If your yard has buckthorn or garlic mustard (another nasty and prolific exotic in the metro area), get rid of it. Buckthorn work can be done now. You might also volunteer to help remove those plants from parks and nature reserves.

Information on buckthorn control can be found on the DNR website: www.dnr.state.mn.us/invasives/terrestrialplants/woody/buckthorn/control.html.

A final note concerning the high diuretic content of buckthorn berries: Keep in mind that they're also not good for jam or jelly.

Jim Williams

http://www.startribune.com/lifestyle/homegarden/blogs/Wingnut.html