Stream Wildlife

     Lancaster County, Pennsylvania has many streams that run through meadows.  Those grassy pastures were originally created along waterways so cattle, horses and other farm animals can get water.  And as the streams turn this way and that in following the lower contours of the land, they create high banks on the outside of the turns where the water moves quickly and erodes the ground, and form mud flats and gravel bars on the inside of each curve where the current flows slower and drops its load of soil, sand and stones.  Certain kinds of vertebrate animals take advantage of each niche along every meadow waterway in this county, as each of their species does elsewhere.
     Some stream banks become up to eight feet high.  At least three kinds of creatures create holes in those banks where they raise young.  Summering belted kingfishers and rough-winged swallows dig burrows into the soil near the tops of the banks.  Kingfishers excavate a few feet back while the much smaller swallows do so for more than a foot.  Kingfishers eat small fish, for which they dive into the water beak-first.  The swallows catch flying insects while on the wing.   
     Muskrats, which look like large meadow mice, dig into the soil at the normal water level so they can swim along the surface of the water and right into their homes without exposing themselves to predators.  After tunneling into the soil more than a foot, the muskrats excavate up to just below the grass roots level so they and their young don't drown during times of high water.  Muskrats eat a variety of vegetation.
     Permanent resident song sparrows also live along streams in meadows.  They shelter and raise young among the tall grasses and bushes along those waterways.  They constantly patrol the mud flats and gravel bars for insects and other kinds of invertebrates. 
     Summering spotted sandpipers and killdeer plovers, which are types of inland shorebirds, are also drawn to the mud flats and gravel bars where they rear offspring and eat invertebrates along the water's edge.  The sandpipers bob as they walk along the shore line.  That dancing mimics debris bouncing in the current, which is a type of camouflage.  In fact, the song sparrows, spotties and killdeer, which are all brown on top, are well camouflaged along their stream habitat.  The killdeer also have black lines through their faces and two black bars on their chests to interrupt their shapes.
     Wherever bridges cross meadow waterways, one to a few pairs of barn swallows build mud pellet cradles on support beams under the bridges.  These swallows, too, seine the air of flying insects, but migrate south in late summer.
     And wherever a bluebird box is erected along the waterway, a pair of tree swallows are the most likely birds to use it to raise babies.  As if with all swallows, they take flying insects from the air and migrate south in late summer and autumn.
     A simple stream in a short-grass cow pasture can be a haven for a variety of wildlife, each one in its own particular niche.  It's interesting to see how tied to their niche each species of life is.