Naturespeak A naturalist's view of the world

May 9, 2011

Black Flies Are Good (Tasting)

Filed under: Uncategorized — wykes @ 9:01 pm

The spillway at Crosswinds Marsh was a hub of activity the other day. The running waters – tumbling over the rocky bottom – were bubbling with life. That life came in two forms. Millions of Black Flies were hatching from the moving water and dozens of birds were there to eat them.  It was a pretty simple bird-eat-bug scenario and one in which the Black Flies played a positive role for a change.

It might seem odd to mention Black Flies as a good thing. For residents of Northern Michigan, these blood-thirsty little demons are not a cause for celebration. The spring hatch means clouds of misery as these tiny flies seek out all patches of unprotected skin in numbers akin to the biblical Egyptian plagues. No, they are a reason to avoid Northern Michigan at certain times of the year. All of this ignores the simple fact that Black flies are found in these places because they can only breed in unpolluted streams and waterways. In other words, they are indicators of good water quality.   Should the Pure Michigan campaign get a hold of this idea they might want to do an ad touting Black Flies as symbols of the pure crystalline waters of our state. “Get bitten by the spirit of the north – come to Michigan.” Well, maybe this wouldn’t go over so well but nothing ventured nothing gained, right?

Fortunately (or is it unfortunately?) Black Flies are not a regular feature of southern Michigan life. It was, therefore, both a surprise and a delight to see them at Crosswinds in such huge numbers. The larvae not only require clean water but they require moving water as well. Attached to the bottom rocks, the bowling pin shaped larvae filter food out of the current. The only moving water at this marsh complex is at the spillway where there is a consistent flow that drains off into a canal.

After a brief pupation, the insects emerge from the water as winged adults (see above). Due to their dark color they are easily identified as Black Flies, but their hump-backed appearance is equally diagnostic. Upon emergence, the adults participate in a mass orgy where males and females pile up in shameless mounds of sexuality. Clumps of flies drift along on the moving water surface. Individuals scampered about like fleas and clambered onto the streamside vegetation and spillway walls (see below).  Their nervous energy certainly charged the air on the day I came upon them and I was not the only one affected.

Dozens of green and white Tree Swallows were feeding on the masses of living chow. There were a few Barn Swallows in the mix, but most were of the Tree persuasion. The birds were swirling about like wind-whipped leaves over the insect studded waters. Their motions were almost mesmerizing – maybe even Zen-like (whatever that means). Watch this little video short here and see what I mean. They were plucking the floating insects off the surface without leaving as much as a ripple in their path.

After a bout of feeding, the birds would perch on a nearby fence to preen and meditate. Their iridescent blue-green backs glittered in the mid-day sun. It was, I’m sure, a banner day to be a swallow. When a bird called a swallow is given the opportunity to do nothing but swallow that is swell thing.

A half dozen Yellow-rumped Warblers also joined in the Black Fly feast. As opposed to the swirling flight tactics of the swallows, the warblers chose to hunt and peck for their daily bread. These brightly colored little birds were driven to near mental collapse by the sheer mass of moving life about them.  I videoed one fellow attempting to make sense of the situation (see here and photo below). It would have made human sense to just sit in one place and peck away as the insect horde moved toward you, but to a bird brain it made better sense to jump about and select at random. I watched them literally gorge themselves on the Black Flies and have little doubt that they’ll be pooping out wings and legs for quite some time.

Considering that I was in the midst of a million Black Flies, I came away from the situation relatively unscathed. I did find a nasty little bite on my hand afterward, but only one. I guess being in the center of the target was the safest place to be – under the diligent protection of the swallows and warblers.

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