Noticeable August Migrants

     August is an exciting month of bird migrations in southeastern Pennsylvania, particularly of southbound shorebirds, swallows and diurnal raptors (hawks and eagles).  Those three groups of birds are easily seen by bird watchers and casual observers aware of those birds' migrations.
     The most regularly seen southbound shorebirds here are lesser yellowlegs and greater yellowlegs, both of which are sandpipers that nested on the shores of lakes in Canada's forests and solitary sandpipers that nest in abandoned birds' nests in trees near lakes in Canada's woods.  And other regularly seen migrant shorebirds here are least, semi-palmated and pectoral sandpipers and semi-palmated plovers, all of which hatch young on the Arctic tundra.  These migrating shorebirds land here and there on mud flats and adjoining shallow water to rest, and feed on small invertebrates they pull from mud and water.  Here in southeastern Pennsylvania farmland they patrol the shores of waterways, impoundments and partly-flooded fields and meadows, after heavy rains, to rest and get food before continuing their travels father south. 
     Little flocks of shorebirds in croplands are interesting to see moving about, exposed, on mud and water, but are often difficult to spot because they blend in to their habitat so well.  They usually are not noted until they move or fly up as a group, swiftly circle their feeding grounds a few times together and, finally, swoop down to land on the same place they just took off from and immediately resume feeding. 
     These southbound shorebirds, and a few other species that are here less regularly and in fewer numbers, come through here from mid-July through September.  But August is the peak time for these shorebirds migrating south to avoid the northern winter.
     Flocks of barn swallows and tree swallows sweep south across this area's farmland in August and September.  Both species nested in southeastern Pennsylvania, but are joined in August by the relatives of each that raised offspring farther north.  Each kind forms flocks of itself, but often the two species create large, mixed gatherings.
     Southward migrating tree swallows form particularly large, inspiring congregations of themselves that sweep over fields by the hundreds to catch flying insects and line up on roadside wires, sometimes in the thousands, to rest and digest between feeding forays.  Tree swallows continue to migrate through this part of Pennsylvania during August, September and into October, but aren't seen here again until April when they return north to rear young.   
     The most regularly seen southbound hawks and eagles in southeastern Pennsylvania in August are broad-winged hawks, ospreys, red-tailed hawks, American kestrels, sharp-shinned hawks and bald eagles.  All of them on migration are entertaining and inspiring.  Broad-wings so south in flocks from eastern North American forests where they raised two young per brood, on average.
     Every morning, except rainy ones, starting in August and peaking in the middle of September, broadies rise from the woods they spent the night in and search for a thermal, which is a column of sun-warmed, rising air.  The broadies drift into the thermal, set their broad wings to catch the rising air and spiral effortlessly up and up with it.  At the top of the thermal, they peel off together and soar southwest in long lines and broad fronts which are thrilling to see.  But the Earth's gravity gradually pulls them down and these hawks must seek another thermal, and another, all day, every day they migrate southwest to Mexico, Central America and northern South America.
     Ospreys and red-tails are big, majestic hawks that mostly soar along the southwest running Appalachian Mountains when wind blows from the north or northwest.  Northwest winds get pushed up the mountains by wind behind them, pushing the hawks up with them.  Ospreys' wings are set in a shallow W while the red-tails' are flat out sails. 
     But ospreys and red-tails soar south off the mountains during west or south winds and can be seen most anywhere over cropland.  Little need then to watch for these hawks along the mountains.  Some ospreys stop at larger waterways and impoundments to catch fish before moving on.
     American kestrels and sharp-shins are both small hawks (a bit larger than robins) that alternate a lot of  rapid wing beats with soaring.  These little hawks often stick to southwest running ridges during north or northwest blowing winds, but scatter south cross-country during south winds.  But wherever they are, they zoom along in swift flight.
     Bald eagles are massive, magnificent birds of prey; thrilling to experience.  They, too, follow Appalachian ridges during northwest winds, but scatter everywhere on south winds.  Bald eagles, like these other kinds of diurnal raptors, can be spotted almost anywhere in this area during August.  Many balds stop at larger waterways and impoundments to catch fish or scavenge dead fish and other animals before continuing on their way south.
     Shorebirds, swallows, raptors and other kinds of birds migrate south in late summer and fall to avoid northern winters.  They do that not to avoid the cold, but to seek reliable sources of food that will sustain through northern winters.  These migrant birds are always inspiring to experience.  They help make August and the months of fall more intriguing.