11/17/20 SUGAR IN THE TREETOPS

I tasted some hackberries yesterday. Like the other hackberries I’ve tried they were very dry but remarkably sweet, like figs. Finding them helped solve a puzzle I’ve been mulling over, and relieved my guilty conscience.

I’d been hoping to find some hackberries, which is not easy at this season since they reside in the tops of female trees only. That they are still available when most of the juicy, desirable berries are long eaten means they’re an important winter staple for frugivorous birds.

Which brings us to the guilty conscience part. For several weeks flocks of Cedar waxwings (the “whistle birds”) have been hanging out in this little forest. During non-breeding season they wander, often in big flocks, seeking fruit. And in the not too distant past, the fruit of invasive plants like Bush honeysuckle, Privet, and Wintercreeper was everywhere in this forest. No longer, thanks to our removal efforts, though these plants are still abundant in surrounding areas.

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Bush honeysuckle berries are produced in huge quantities on mature shrubs.

This massive, rapid change in a “novel” ecosystem is bound to have effects, and hopefully in the long run they will be positive. But there is no doubt the reason avian frugivores are thriving, and their populations are increasing, is from feeding on and dispersing the fruits of invasive shrubs and vines.

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Cedar waxwings feeding on Greenbriar berries

So my first thought, when I see waxwings, is what are they finding to eat. In the understory, berries (except for Coralberry which seems to be survival fare only) are extremely scarce. But there was a clue – for the most part the Waxwings were moving about high in the treetops. Thinking about which tall trees might still have fruit at this season, I settled on Hackberry, Celtis occidentalis. And in the in Missouri Dept. of Conservation entry for Hackberry was this – “Flocks of cedar waxwings congregate to devour the fruits.” Ha, mystery solved! Hackberry is an abundant tree in this forest; the many tall, older ones spread their branches widely above the canopy.

The largest Hackberry in the forest has a hollow on one side, with enough rich humus to support a huge Spotted jewelweed plant.

The fact that the fruits are so dry means they preserve well despite their high sugar content. A more southerly species of Celtis is actually called Sugarberry (Celtis laevigata); in addition to being so valuable for wildlife the berries of all species have been utilized by native peoples. (In fact, these unassuming little fruits may be one of the oldest known foraged foods.) Though the thin outer layer of pulp is the only part utilized by birds, it’s relatively rich in protein and fat as well. Compared to the abundant but nutritionally insipid Bush honeysuckle fruits, hackberries are a much better deal.

So now I will rest easier, knowing that waxwings can still find winter food in this little forest, as they always did. And they’ll be planting plenty of Hackberry trees while they’re at it.

Sometimes I was lucky enough to see them foraging down

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