Cow Pasture Streams

     The slow-moving, deeper parts, "holes", of clear, running streams in sunny cow pastures in southeastern Pennsylvania are one of my favorite habitats to experience in summer.  Those waterways don't always appear so, but they are full of attractive, adaptable and interesting creatures of several kinds.
     Bluet damselflies, green darner dragonflies and white-tailed and twelve-spotted skimmer dragonflies are some of the first critters noticed at these streams.  These common members of the dragonfly family are often obvious because they zip through the air over streams, ponds and meadows in pursuit of flying insects to eat, and mates.  Bluets are tiny, thin strips of blue, white-tails have white abdomens and twelve-spots have 12 black and white spots on their four wings, two white and one black on each wing.  And the three-inch-long green darners have green thoraxes and blue abdomens. 
     Females of each kind of damselfly and dragonfly spawn eggs in the slower sections of these streams, and in ponds.  The brownish nymphs of each species feed on aquatic invertebrates, tadpoles and other small, water critters on the bottoms of those waters until they morph as winged adults and escape the water for life in the air when we see them, sometimes in abundance.
     Female mallard ducks raise broods of ducklings on ponds and some cow pasture streams.  The young consume invertebrates to grow rapidly, while their mothers concentrate mostly on plant life.
    A type of bug called water striders walks on the surface of water in stream holes, and ponds.  These insects are dark on top and silvery below, which blends them into their stream habitat.  The six legs of striders spread their slight weight over the water's surface tension to the extent they don't break through it; sort of like the use of snowshoes on snow.  Their pair of middle legs propel them across the surface of the water and their front legs capture land invertebrates that fell helpless on the water's surface.  
     A variety of fish congregate in the slower holes in meadow streams, including Johnny darters, black-nosed dace, banded killifish, white suckers and carp.  All these fish species are basically brown, which camouflages them against the stony or muddy bottoms of the streams.  Darters have no air bladders to hold them in mid-stream, so they lie on the bottom where they ingest tiny invertebrates and other small critters.  Schools of dace and killifish, often in mixed groups, hunt invertebrates in mid-stream.  White suckers and carp consume both plant and animal material, but mostly off the bottoms of the streams.  The different foods in different parts of streams reduce competition for food among these fish species.
     Looking like tiny lobsters, crayfish, which are a kind of freshwater crustacean, live under stones and patches of vegetation on the bottoms of flowing waterways.  But sometimes they can be spotted moving over the bottoms of those streams in search of bits of plants and animals. 
     Muskrats, which are rodents that resemble big meadow mice, dig holes into stream banks at the normal water level, then dig uphill in those banks.  Muskrats eat cattail roots, grass and other kinds of vegetation growing near water.
     Great blue herons, great egrets, green herons, mink and raccoons patrol some of these pasture waterways to get food.  Coons get mostly crayfish and frogs, while mink capture those same foods, and some of the larger fish.  Herons and egrets snare all those creatures, and mice in the meadow.  Interestingly, herons and egrets dunk the mice they catch in water to slick the rodents' fur so they can swallow them more easily.
     Some herons, coons and mink live and rear young near some cow pasture streams.  Herons build stick cradles in trees, raccoons live in burrows in trees and the ground and mink live in abandoned muskrat holes in stream banks and in muskrat burrows of those muskrats they killed and ingested.
     Belted kingfishers and rough-winged swallows both dig nesting burrows near the tops of stream banks.  The kingfishers catch and eat small fish while the swallows consume flying insects.
     Colonies of green frogs and small groups of painted turtles sit on top of aquatic plants in the slower holes of pasture streams.  The frogs sit there, half-submerged, to catch and eat invertebrates and to croak to attract females for spawning in the slower water.  The turtles are there to soak up the warming sunlight so they have energy to look for food and mates.
     Fowler's toads also spawn in the slower stretches of meadow streams.  I hear their short, nasal "waaaah" many times during June nights.
     Snapping turtles and northern water snakes live in many slower holes in pasture waterways.  Both these creatures are completely predatory, feeding on fish, frogs, tadpoles and other aquatic creatures.  They, too, sunbathe, but not obviously.
     Red-winged blackbirds and song sparrows live and nest along meadow streams wherever grasses and cattails grow high enough for these two bird species to find enough shelter to construct grassy nests.  Female red-wings build nurseries up the stems and female sparrows make cradles on the ground at the bases of the plants.  Both species feed on invertebrates.                 
     Little groups of attractive American goldfinches visit pasture streams to eat alga in the shallows.  Male goldfinches in summer are yellow and black, adding more beauty to the waterways and pastures.
     Watch streams in meadows during summer more closely.  They are full of interesting, adaptable life, making our lives more enjoyable.  Or look at other habitats of interest near your homes more closely.  They, too, probably are full of intriguing, beautiful life.