Birds on the Move in July

     March, April and early May in Lancaster County, Pennsylvania see many kinds of birds pushing north to nesting territories.  Mid-May to early July is the time of nesting birds of many species here.  And the middle of July, through August, in this area, witnesses a variety of post-breeding bird species already on the move in preparation of the coming fall and winter.
     Five types of sandpipers, least, pectoral and solitary, and lesser and greater yellowlegs, which are other species of sandpipers, wing south from farther north in July, many of them settling on mud flats and shallow water along waterways, impoundments and puddles in flooded fields and pastures in Lancaster County.  For several days here they eat invertebrates they pull from the mud before continuing their migrations farther south.  The short-legged least and pectoral sandpipers get food from the flats and inch-deep water while the solitaries and yellowlegs catch invertebrates in mud under deeper water.  That dispersion reduces competition for food among these related bird species.
     Least and pectoral sandpipers are brown, which camouflages them on mud.  Solitaries and both kinds of yellowlegs are grayish, allowing them to blend into the color of water.
     Least and pectoral sandpipers nest on the ground of the Arctic tundra.  But solitaries and yellowlegs hatch young along the shores of lakes in forests in Canada.  Interestingly, solitaries use abandoned birds' nests in trees to hatch offspring.  They are the only kind of shorebird that does that.  And solitaries are the only shorebirds that flutter delicately on the wing like butterflies.
     Those sandpipers come south in search of feeding grounds before the north freezes shut, locking away their invertebrate food supply.  In fact, most birds migrate south, not to avoid the cold, but to find food supplies during the northern winter.
     Many post-breeding great egrets, snowy egrets and little blue herons, in that order of abundance, wander north in July to find fairly unused fishing places where they can fatten up and recuperate before the rigors of winter.  The egrets and immature little blues are white, making them noticeable along the waterways and impoundments they frequent to catch fish, frogs, tadpoles and other kinds of aquatic creatures.  But as the average temperatures become colder in autumn, these egrets and herons drift south again in search of open water and reliable food supplies to get them through the northern winter.
     And while the sandpipers are coming south and the egrets and herons are wandering north, local, post-breeding barn swallows and tree swallows gather into flocks in local farmland in preparation for their flights south in search of reliable supplies of flying insects to eat through the northern winter.  These swallows congregate in mixed groups or in their own gatherings and fly over fields and larger impoundments in masses to feed on flying insects.  Their swift, interweaving flights among their fellows, without collision, after food is entertaining to watch.  When full, the swallows rest and digest on tree twigs and roadside wires in large numbers.  They are more noticeable on roadside wires and one can see how large their flocks can get as they continue to gather before meandering south for the winter.
     Lancaster County in July is full of flocks of birds on the move.  They make this area more interesting and inspiring to anyone who takes the time to watch for their annual migrations south.