Invasive honeysuckles and birds

 

A western Ohio woodland, its understory utterly dominated by Amur Honeysuckle (Lonicera maackii). While there are other species of Asiatic honeysuckles running amok in the Midwest, this one is by far the worst culprit in most areas I visit. It is firmly entrenched in our flora, much to the detriment of the indigenous plants.

As always, click the image to enlarge

It wasn't always so. The nonnative bush honeysuckles like Amur Honeysuckle weren't a major problem until fairly recently. In Lucy Braun's The Woody Plants of Ohio (1961), she devotes a scant two sentences to it. Braun knew it only in the wild from the far southwestern corner of Ohio (Hamilton County) but did note that it was "becoming abundant".

This map is from Tom Cooperrider's decidedly unsexily titled The Dicotyledoneae of Ohio: Part 2: Linaceae through Campanulaceae. The book was published in 1995 and gives a snapshot of the progress of Amur Honeysuckle in Ohio. Twenty counties have been added since Braun's publication 34 years prior. It should be noted that botanical works such as these rely on vouchered specimens as evidence, and there are relatively few botanists that collect and archive material in herbaria. By 1995, Amur Honeysuckle was undoubtedly in counties beyond those depicted on this map but was definitely not the scourge it is now.

Cut to today, and documentation of the horror show that Amur Honeysuckle has become. The orange squares representing reports congeal into blobs, so frequent are the observations. This is part of the iNaturalist map, which relies on peer-reviewed photos submitted by observers. Ohio is smack in the middle of this snippet of the map, and honeysuckle pretty well blankets the state. Good old Lonicera maackii is certainly in all 88 counties, and at least locally abundant in many or most of them.

How did it get here? Apparently, the original escapes came from the New York Botanical Garden, which began promoting Amur Honeysuckle as an ornamental in 1898. By the 1930's and '40's, wildlife agencies greatly exacerbated the problem-to-be by widely promoting honeysuckle as a ground cover, soil stabilizer, and wildlife food plant. As often seems to happen with invasives, there was a few decades long gestation period where the plant did not run amok, but probably largely stayed where it was put. In Ohio and this region of the Midwest, the spread probably began in earnest in the 1980's and the trajectory was obvious by the time of Cooperider's 1995 book. One need only glance at the iNaturalist map to see what has happened since.

Small wonder people were smitten with Amur Honeysuckle. It is pleasing in form, and sports abundant showy white flowers.

Alas, those flowers later become equally showy fruit, also abundant. Brightly colored berries probably evolved to lure agents of dispersal, especially birds. Birds are drawn to bright fruit, and it is to the honeysuckle's advantage to have its berries eaten by highly mobile winged creatures. A frugivorous (fruit-eating) bird might expel the seeds a long distance away, effectively playing the unwitting role of avian Johnny Appleseeds. Birds are surely the primary reason for the remarkably rapid invasion across a broad swath of eastern North America.

An American Robin (Turdus migratorius) sits among a sea of Amur Honeysuckle fruit. It is akin to a kid in a bowl of M & M's. The 50-acre preserve where I made this shot is in Columbus, and I visited last Sunday. The site was thoroughly infested with honeysuckle, and dozens if not hundreds of robins gorged themselves on the fruit.

A first-year White-throated Sparrow (Zonotrichia albicollis) caught in the act, berry in beak. This species is probably our most abundant migratory sparrow, and many were present here - same site as the robin above.

With abundant frugivores such as the American Robin and White-throated Sparrow (not a major frugivore but nonetheless they have a taste for honeysuckle berries) eating this stuff, it's small wonder that honeysuckle has spread so rapidly and continues to do so. Many other bird species eat it as well including a hyper-abundant nonnative, the European Starling (Sturnis vulgaris). What is curious to me is the apparent lag time from when Amur Honeysuckle began to be planted commonly (1930's-40's), to when it became an obvious and worsening invasive plant (1980's). I wonder if birds, confronted rather abruptly with a completely foreign plant, basically ignore it for a while, not recognizing a potential food source. Maybe it takes a few decades for the feathered crowd to develop a taste for the stuff and begin ravishing it in earnest. But once they do, the game is over.

Amur Honeysuckle is so thoroughly entrenched now that there is no way to eliminate the overwhelming majority of it. Localized control in targeted parks and natural areas can be successful but constant vigilance is necessary as new seed sources will be introduced annually.

We can hope that Amur Honeysuckle eventually runs its course, and fades out, as some invasive species seem to do. But there's no sign of that happening yet.

A trip to Slate Run Metro Park: Botanical highs and lows

Part of a large wetland complex at Slate Run Metro Park in Pickaway County, Ohio. A section of the westernmost part of this 1,705 acre park is a mosaic of meadows, ponds, and wetlands.

It's sometimes easy to overlook the jewels in one's own backyard. Even though Slate Run is only a bit over a half-hour's drive, and it's been there for a while, I had never been to the place. That situation got remedied with two visits in the past few days, and I was impressed with what I found.

Immediately upon arrival, it was birds galore, and since finding and imaging the feathered crowd was the foremost priority of these expeditions, I was pleased indeed. Columbus and Franklin County Metro Parks (wish they'd shorten that name! "Franklin County Metroparks") has long been a leader in ecological restoration and it shows at this park. Lots of native plant diversity in the wetlands and fields, and a logical blend of uplands and lowlands.

The Kokomo Wetland Trail winds for about 1.5 miles through meadow and along wetlands. At one point, a boardwalk crosses a pond/wetland. I found lots of birds along this trail, including many Swamp Sparrows. This is a hardy species, and many try to overwinter here, especially in sites with thick cattail stands.

Slate Run was rich in sparrows during my visit, and their ranks included American Tree Sparrow, Song Sparrow, White-crowned Sparrow, White-throated Sparrow, Fox Sparrow, Field Sparrow, Dark-eyed Junco, and Eastern Towhee.

One honey hole was a photographer's dream. As soon as I got out of the car, I saw and heard numerous American Robins and Cedar Waxwings. It didn't take long to figure out that many of the birds were venturing to a small pond buffered by woods, and drinking and bathing.

I crept into a good situation, and after a while the birds acclimated to my presence and carried on with their activities. This robin is perched on a perfectly sited log, which many of the birds used as a stop before or after a visit to the nearby water. While I like robins - one of the handsomest birds in North America, we're just jaded because they are so common - I've got scores of photos of them, and really hoped that a waxwing would tee up in this same spot.

Voila! Before long, a Cedar Waxwing did just that. Few of the world's birds can rival this elegant species for suave sophistication.

After a while, waxwings began coming so close that I couldn't even focus - they were inside my minimum focus range. Such problems!

The birds' close proximity allowed me to create portraiture shots such as this. This adult waxwing is impeccably groomed, as is typical.

In a minute, I'll discuss the abundant food source that had so many birds concentrated in this area. But with the waxwings, what I really wanted was to make some photos of them eating their botanical namesake: the fruit (cones) of eastern red cedar, Juniperus virginiana. This native conifer provides an important winter food source. There were a few cedar very close at hand, and eventually several of the birds flew in and began plundering the fruit. One cedar was so close that I would have needed my 70-200mm lens to capture the birds in its boughs - the 500mm plus 1.4x teleconverter was overkill.

A waxwing poses, briefly, with berry in bill. A second later it was down the hatch.

The new norm for many Ohio woodlands is this nasty plant, Amur honeysuckle, Lonicera maackii. A native of Eurasia, it was intentionally introduced in eastern North America long ago, partly for its ornamental value, and partly for its "wildlife value".

Even this late in the year, the leaves of this understory plant remain green, and its branches drip with bright red berries. And the birds love 'em.

Amazingly, the various bush honeysuckles (there are a few invasive species) were still formally recommended as a wildlife planting by wildlife agencies into the 1990's - long after botanists and ecologists could have told them that this was a bad idea. The nursery trade must be implicated in this infestation, too, although I think by now virtually everyone has wised up and stopped selling the stuff.

But honeysuckle is here to stay, at least for the foreseeable future. Even in a managed park such as Slate Run, there is far too much of it to eradicate.

A Northern Cardinal plows through a honeysuckle berry, one of many that I watched it eat. And he, and all of the other birds feeding on the stuff, will spread the plants about. Some of the seeds survive the rough ride through the digestive tract and emerge from the other end scarified and ready to grow.


I was pleased to hear the loud smacking CHAK! calls of a Fox Sparrow, and eventually saw 5 or 6 of the large handsome sparrows. I was not so pleased to see them succumbing to the honeysuckle addiction shared by many of their feathered companions. Note the evidence on the tip of this bird's bill.

Dozens of American Robins were in the area, and all of them were feeding heavily on the honeysuckle. These thrushes are one of the major consumers of honeysuckle fruit, and the plant is a primary reason why we in the north see so many robins around in winter. The Cedar Wawings were also consuming honeysuckle fruit en masse, but I preferred to use my shots of them eating the native cedar fruit.

Even the White-throated Sparrows were in on the act. This handsome white-striped morph ate many of the berries while I watched, as did many of his companions.

So, if honeysuckle is such an abundant and rich source of bird food, what's the problem?

For one, the berries themselves. They are high in sugar and low in fat and protein - exactly the opposite of what birds need in winter. Native berry-producing shrubs produce far less fruit, but it provides much better nutritional needs for birds that might be subjected to severe cold snaps and ice storms which might largely lock the birds out of many food sources for days on end.

Too, the absolutely enormous berry crops lure many species to overwinter in much greater numbers far to the north of where they normally would. Like all those robins. This creates the potential for large winter die-off's, as has happened conspicuously with American Robins, should extended severe weather strike.

Honeysuckle also forms extensive tangles that choke out many/most native shrubs and other plants. It has been shown to be allelopathic as well - the roots exude enzymes which inhibit the growth of competing plant species. Botanical chemical warfare, if you will.

Perhaps most insidiously, the nonnative honeysuckles are unsuitable hosts for nearly all of our (in Ohio) 2,500+ moth and butterfly species. Their caterpillars cannot eat the stuff, because they share no evolutionary history. This means vast swaths of honeysuckle infestations that do not produce the caterpillars that are so essential to fueling our nesting and migrant songbirds.

On its face, the honeysuckle might seem a great thing for birds. But there is a much darker side to this story.