Sunday, December 14, 2008

Bushes of M & M's

(Footnote: I understand the role of a paragraph in writing, really, I do. They're great. Paragraphs break up long blocks of text and make things oh so much more readable. But those of us that are longtime users of Blogger, the wondrous machine that enables us to make these posts, know of its foibles. And one of those is the occasional inability to insert a space between paragraphs. I tried, but the Blogger Gods kept scrunching everything back together. Maybe it's some act of stupidity on my part. Maybe a more knowledgeable Blogger Pilot can tell me what is going wrong and how to fix it. In any event, I apologize for the run-on paragraphs)

I was afield today, helping find birds as part of the annual Columbus Christmas Bird Count. The south side of town is my domain, and I get into some spots that I normally don't frequent. The above is one of them. We are looking west down Hart Rd., which runs off of Harmon Avenue. This year, the extreme fruit production of the Amur Honeysuckle, Lonicera maackii, really caught my eye. That's what all of those shrubs lining the roadway are, and so copiously loaded with berries are they that their collective masses created a reddish bloom to the shrubscape.

A closeup view of Amur Honeysuckle berries. Kind of showy, I suppose, and you can see why misguided landscapers might wish to grow it. But like The Blob, bush honeysuckle has gotten totally out of hand and now ravages the landscape. In a season of plentiful fruit, like this one, there must be literally millions of berries on bushes in Franklin County alone!
And those berries are bad news, as we shall see. But so is the physical structure and density of the shrubs themselves. So prolific are the honeysuckle that it utterly displaces native flora in many areas. Some think that the plant is also allelopathic; that is, it produces enzymes from the roots that inhibit the growth of other plants. I am a believer in the allelopathic theory, as the understory of a honeysuckle thicket is mostly barren earth. In native stands of shrubs, such as Spicebush, Lindera benzoin, one finds many other native plants. The massive underground root systems of large honeysuckle stands also drain moisture from the soil, drying the habitat and making it even more inhospitable for the plants that should be there.
The structure of honeysuckle shrubs does not lend itself to successful nesting, either. Studies have shown that the open habit of the shrubs offer less concealment to predators, and once a nest has been spotted, it is easier for predatory animals to climb and pillage.
There were hundreds of American Robins along Hart Road, feasting on the honeysuckle fruit. I caught some in the act, such as this female robin. Nearly everywhere I went today, robins were in evidence, feasting on this nasty invasive. So were lots of White-throated Sparrows.
Interestingly, the few Cedar Waxwings that I found were eating the fruit of a native tree, Hackberry, Celtis occidentalis. But in general waxwings prefer feeding higher off the ground, while white-throats and robins occupy niches on or near the ground. That's not to say waxwings won't eat this stuff, because they will.

Beautiful male American Robin, scarfing down oodles of berries. Ironically, native birds like robins are major vectors in the spread of invasive honeysuckles, and other non-native berry producing plants. But just like the native flora displaced by the honeysuckle, these birds too can pay a price.
And now to the M & M analogy. Honeysuckle fruit certainly look good, and judging by the way the hordes of robins wolf them down, they must be tasty. Had I had my choice between eating bags of M & M's as a kid, or spinach, liver, and broccoli, it would have been the little round confections every time. And my health would have suffered greatly for it.
Same with the birds. The honeysuckle fruit are primarily mostly made up of carbohydrates, and lack the important fats and nutrients that are often abundant in native shrub and tree fruit. So, this artificial bounty of berries entices huge numbers of robins and some other species to winter well north of where they normally would. All may be fine, until they got socked with a spell of brutal winter weather, with extended subzero temps, frozen ground, and ice. Then, the energy provided by honeysuckle is quickly depleted and mortality spikes sharply.
We saw this here in Columbus a few winters back, when a severe winter storm triggered the death of probably thousands of robins.
The web of ecological consequences spawned by invaders such as bush honeysuckle is often far-reaching and insidious, and generally not foreseen when these invasives are first touted as landscaping gems.
Do the world a favor - destroy a bush honeysuckle!


Anonymous said...

I love finding and watching robins feeding in berry bushes. They can be so acrobatic in the process of getting their snacks and meals.

Happy Holidays

Anonymous said...

The focus of my work revolves around how migrants birds use these non-native species. From hundreds of seeds collected in fecal samples so far, it looks like honeysuckles are preferred by migrants even when native species are available. Recent research also indicates that the physiology of migrants actually changes during migration, so that their nutritional needs are different, and they can assimilate nutrients in a different way. At least for migrants, it looks like it's not so simple as "carbs bad, fats good."

I'm certainly not a proponent of invasive species, but these plants do serve an ecological function. If native plants are not available it may not be wise to rip out all honeysuckles if alternatives aren't in place.

John Lennon said...

About ten years ago I replaced half of my honeysuckle with spicebush, and was going to replace the rest of it once the spicebush got established. But the honeysuckle produced so much more food than the natives, that I decided to leave it in. Plus, my bees absolutely love the honeysuckle. I've heard the native berries are more nutritious, but I've never been able to find any peer reviewed research on the matter, and at least in my back yard, I'd have to be shown that 1 native berry is better than 5-10 of the honeysuckle berries, because that's the ratio I get. Carolina wrens and cardinals have been succesfully breeding in the invasives for years.

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