Indigos and Blue Grosbeaks

     Over many years, I have heard and seen many male indigo buntings singing from a tree top or a roadside wire in farmland in southeastern Pennsylvania, as elsewhere.  And more recently, I have experienced male blue grosbeaks on wires in overgrown habitats of this same area.  I always enjoy the males' lovely songs and marvel at their handsome feathering.  The songs of indigos, I think,  are particularly touching.  I remember, as a boy, sitting at church camp vespers on a farmland hilltop on sunny summer evenings and paying more attention to the intrigue of distant wooded hills and the melancholy singing of a nearby male indigo than I did to the service I was supposed to be listening to.  That bird sang until the sun sank behind the mountains.    
     Indigo buntings and blue grosbeaks are bird species that nest in overgrown thickets in hedgerows, woodland edges and roadsides in farmland here in southeastern Pennsylvania, and through much of the United States.  These species have much in common, including both being members of the Fringillidae (seed-eating) family, which includes sparrows, finches, buntings and grosbeaks.  Male indigos and blue grosbeaks are deep-blue all over.  Females of both types, however, are brown, which camouflages them around their nests.  Both kinds have thick beaks they use to crack open seeds.  And both raise young in open nests in shrubbery in weedy habitats, and sing beautifully high in trees or bushes, and on roadside wires.  But why are these species so similar in appearance, habits and habitats?  Are they closely related, did the habitat they share shape them, or both?  Blue grosbeaks are sometimes called "large buntings".
     Indigos nest in the eastern United States and winter in Central America.  They are sparrow-sized, slim and often called "blue canaries" because the males are blue.  Males' songs are long, varied and with twice-repeated notes in each series of notes that are enjoyable to hear.  Indigos often sing during the heat of mid-day when most other bird species, except red-eyed vireos in the woods, are silent.       
     Blue grosbeaks raise young in the southern United States from coast to coast, but are slowly pushing north.  They have been nesting here in southeastern Pennsylvania for about 40 years.  They, too, winter in Central America. 
     Blue grosbeaks are much like indigos, but chunkier and half again as big.  And both genders of this species have two chestnut bars on each wing.  Males sing rich, warbling songs that can be long at times, but enjoyable to listen to. 
     Indigo buntings and blue grosbeaks are beautiful, similar birds with pretty songs.  But, for the most part, only the males are seen when singing from lofty, exposed perches.  Females and young stick to the protective cover they favor.  As to why they are so similar, I don't know.  But I suspect their shared habitat made them the way they are.