HOLES IN MEADOW BROOKS AND STREAMS

     Many cow pastures of green grass in southeastern Pennsylvania farmland have a brook or stream flowing sparkling-clear through them.  Those pretty, little waterways provide fresh water for grazing livestock.  Currents of some of those brooks and streams gouge out mud and stones, here and there, from waterway bottoms, creating small, deeper "holes" in them.  The current is slower in those little holes, providing places where wildlife settles without having to battle stronger currents as they would in shallow water.  Green alga grows on some of the rocks in those holes and tall grass and other plants, including forget-me-nots, arrowheads, smartweeds, evening primrose, bur-marigolds, sneezeweeds and bittersweet nightshade, flourish on the edges of many holes.  

     Several kinds of aquatic creatures live in those small "holes" in meadow waterways.  But each hole harbors a unique community of critters; no two hole communities are alike.  

     Little schools of stream-lined black-nosed dace, blunt-nosed minnows, killifish and chubs constantly undulate into the currents of clear waterways while they watch for invertebrates to ingest.  All these small, mostly grey-brown fish are hard to see because they are camouflaged before the rocks and mud on the bottom.  Sometimes, I see their dark shadows on waterway bottoms before I see the fish themselves.  And all these kinds of little fish, except the killifish, have a black streak on each flank from nose to tail.  Those streaks break-up their shapes, which is another form of blending in.  Still, herons and water snakes catch and eat some of these small, freshwater fish.

     Crayfish, a kind of shelled crustacean like shrimp, lurk on the stony, muddy bottoms of holes.  Growing up to six inches long, they use their large, front claws to grab and scavenge any bits of plant and animal material to feast on, and they hide under rocks when at rest.  

     Each crayfish walks forward, but rapidly swims backward with an abrupt, forward thrust of its tail, an action that confuses herons, raccoons, mink and other kinds of predators who try to catch crayfish.

     Female crayfish carry eggs and tiny young on swimmerets under their tails to protect that progeny.  The young leave on their own when they get too big to carry.  

     Water striders are insects that walk on surfaces of water in holes, while they watch for helpless invertebrates floating on the water's surface.  Striders' long, ski-like legs spread their weight across the water so they float, and those legs rapidly propel them over the surface to catch victims.  Striders are dark on top and white below, which allows them to blend into their watery habitat.

     Beautifully-blue and very slender bluet damselflies, and an occasional dragonfly, skim over the water of holes in pursuit of flying insects to eat.  Some of the damsels spawn into the holes where their nymphs live under stones on the bottom and hunt tiny invertebrates to eat.

     Green frogs and muskrats live along some of these little holes in pasture waterways.  The frogs sit on shores and snap up invertebrates to consume.  The 'rats ingest grass and other meadow plants by the water and live in dens they dig in streambanks.  Both frogs and muskrats, however, are always alert for marauding mink, raccoons and great horned owls who would eat them. 

     Song sparrows, gray catbirds, common yellowthroat warblers and red-winged blackbirds are songbirds that nest sparingly in tall plants, vines and shrubbery by these little holes in meadows.  But only the song sparrows live there permanently.  Song sparrows play the role of sandpipers by walking and hopping along muddy shores where they pick up invertebrates and seeds to eat the year around.

     Though small holes of deeper water in meadow brooks and streams, they harbor a lot of charming, interesting wildlife.  Fortunately, the water is usually clear enough to see those creatures going about their daily business of living.