do birds eat buckthorn berries

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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, shes not getting a diamond. Shes getting cut glass. Worse yet, the gift probably will give her diarrhea. Bad start on his part.

Buckthorn is ubiquitous in the metro area, certainly in my eastern Orono neighborhood. If you look closely at yard edges, its 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.

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 Im 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 nations 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.

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

Are the birds truly being poisoned? Canada moonseed

I was curious about why a plant that needs birds to help spread its seeds would want to harm them. The pieces did not fit. A detailed 2011 blog post by Julie Craves, then at the University of Michigan-Dearborn, got me even more interested in buckthorn’s effects on birds. She noted how little peer-reviewed work existed regarding buckthorn poisoning of birds. Wild rosehips

She maintained that what could be regarded as buckthorn’s “laxative effect” is actually just what occurs when birds consume fruit that has a particular nutrient profile. Put another way, it is necessary to compare the laxative properties of buckthorn’s drupes (berries) to those of other fleshy fruits. Menispermum canadense (Canada moonseed), Vitis riparia (wild grapes), and Rosa spp. (wild roses) are a few examples. Like many buckthorns, these species can all produce fruit that lasts from late fall into winter.

Emodin, a substance found in buckthorn fruit, is commonly held responsible for harming birds. Emodin is found in the leaves of the native Minnesota buckthorn species, alder-leaved buckthorn (Rhamnus alnifolia), though I’m not sure if it’s also present in the berries. Thus, emodin predated the introduction of invasive common (Rhamnus cathartica) and glossy (Frangula alnus) buckthorn in the woodlands of our state.

We know emodin can cause laxative effects in mammals. However, very few studies have looked at how it affects birds. Unripe berries from buckthorn species often test high for emodin. However, as the fruit ripens, especially in common buckthorn, the concentration of emodin drastically decreases. Many bird species, particularly robins and cedar waxwings, feed on ripe buckthorn fruit.

The cedar waxwing in the picture is presenting a buckthorn berry as a courtship gift to his intended mate. One could argue that the berry and an engagement ring are interchangeable.

Parent birds may be wasting time and energy if they hunt buckthorn or certain other invasive shrubs for nestling food. For example, if there is a lot of buckthorn in the nearest vegetation, the parents have to fly farther and put in more effort to get food.

However, he noted in an email that some ornithologists view the berries as junk food due to their low fat content. That would make them inadequate for a pre-migration diet or as food for chicks.

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

Chickadees nest in our yard. Their chicks are fed insects, primarily the high-fat and high-protein caterpillars of butterflies and moths. Those nutrients are important to the rapidly maturing young birds.

Emodin’s effects on birds  A robin eating buckthorn fruit. Photo:

In contrast to Morrow’s honeysuckle (Lonicera morrowii) or chokecherry (Prunus virginiana) fruit, birds regularly avoided eating unripe buckthorn berries in a 1972 study that suggested they were sensitive to the amount of emodin present. In an effort to “trick” the birds, researchers also sprayed chokecherries with emodin, but the animals sensed something wasn’t quite right. The birds didn’t get sick until they were force-fed a lot of unripe buckthorn fruit. It makes sense that birds arent attracted to unripe fruit. Ripe plants yield sweeter fruit. These that depend on birds and other animals for pollination This prevents animals from dispersing immature seeds that have poor germination rates.

This 1972 study used lab-bred birds and may be the source of the myth surrounding emodin poisoning. This is significant because, in the wild, birds may find other, more favored food sources besides unripe buckthorn berries. Evidence suggests that the effects of emodin may also vary depending on the species of bird. For one Asian species, the yellow-vented bulbul, emodin actually slowed down rather than accelerated digestion.

FAQ

What birds eat buckthorn?

Wildlife: Mice and red squirrels as well as birds, like cedar waxwings and robins, eat and disperse the seeds. But Buckthorn berries are not particularly nutritious (they are mostly carbohydrates and low in protein), so few native animals rely on them as a food source.

Should I remove buckthorn from my yard?

By removing buckthorn plants on your own property you prevent the dispersal of seeds to other land. We need your help removing buckthorn from our community forest! Note: Common and Glossy Buckthorn are considered to be RESTRICTED NOXIOUS WEEDS by the Minnesota Department of Agriculture.

Are buckthorn berries poisonous to animals?

Berries are slightly toxic and act as a laxative when ingested by wildlife, which helps the plan spread spread easily. Emits a chemical called “Emodin” into the ground, which is toxic for plants and animals.

Do Robins eat buckthorn?

Ripe buckthorn fruit is fed upon by a variety of bird species, especially robins and cedar waxwings.