Robins and Bluebirds

     A scattered flock of about 120 American robins ran and stopped, ran and stopped, as they listened and watched for earthworms and other kinds of invertebrates on a greening meadow in mid-March of this year.  A few days later,I saw several robins, and a pair of mallard ducks, a killdeer plover and two male red-winged blackbirds getting a variety of foods along a clear rivulet bordered by lush, green grass.
     The robins and other birds were lovely sights in those human-made habitats.  And those robins had just come north for the nesting season, much to the thrill of people who were waiting for those birds' spring arrival.  At that time, and through the rest of March, robins seem to be most everywhere- on lawns, bare-ground fields and along tiny waterways. 
     Some robins and eastern bluebirds spend winters in southeastern Pennsylvania, but others drift south to escape the northern winter.  The birds that stay north consume berries in hedgerows, woodland edges and suburban areas.  But those individuals that went south, suddenly return north by the middle of March, to the joy of many people. 
     The attractive robins and bluebirds are related to each other in the thrush family.  Fledgling robins and bluebirds have spotted chests, as do thrushes.  But adult robins and bluebirds have reddish-brown chests.
     Toward late March, each male robin repeatedly sings his lusty melodies from trees and shrubs on lawns to establish his territory and attract a mate for raising young.  Robins mostly sing before sunrise when younger suburban areas ring with many robin concerts at once.  But robins utter their sweet songs any time of day, including after sunset.  
     And by late March, male bluebirds sing their delightfully gentle phrases of three or four whistled notes while perched on fence posts and tree twigs on the edges of fields and meadows.  The male bluebird, himself, is striking with the blue sky on his upper parts and the Earth on his chest.
     By early April, female robins and bluebirds look for nesting sites, the robins in the forks of trees and bushes in suburban areas.  Female bluebirds search for tree cavities created by woodpeckers or wind ripping limbs off trees, exposing the wood to agents of decay.  They look for those hollows in trees in meadows, hedgerows and woodland edges.
     Some people erect bird houses in weedy pastures and field edges especially for bluebirds to nest in.  And that species does, if not chased out by house wrens, house sparrows or tree swallows.  Placing bluebird houses in the right habitat is the key to keeping away much of the feathered competition for those boxes.  House wrens prefer woodland edges and house sparrows like to be around buildings.  But tree swallows enjoy much the same habitat as bluebirds.  Incidentally, an entrance diameter of one and a half inches will keep starlings from taking over bluebird boxes.  
     By mid-April, female robins and bluebirds build nurseries.  Robins use mud and grass to create open cups among twigs in trees and shrubs.  Bluebirds layer grass in tree cavities and bird boxes.  Each female of both related species lays an average of four blue eggs in her cradle.  The young hatch about twelve days later and fledge their nurseries toward the end of May.  Many females of both kinds soon start a second brood that fledges by late July.
     Interestingly, American robins and eastern bluebirds, as species, have benefited from Europeans' clearing of forests in the eastern United States to create farmland.  Several kinds of spot-breasted thrushes thrived in those seemingly unending woodlands.  Robins and bluebirds, however, were restricted to woodland clearings that had some shrubbery and trees, but were limited in acreage.  But when those forests were cut away for fields and pastures, spot-breasted thrushes retreated with the woods, but robins and bluebirds expanded their ranges and numbers with the unrelenting expansion of farmland that was created.  Today robins are adapted mostly to younger suburbs and bluebirds have adjusted to weedy fields, both of which are human-made habitats.             
     Robins and bluebirds are common today in the built habitats they adapted to.  And each kind of bird brings much beauty and intrigue to the habitat it reigns in.  We are blessed with their presence.