An Example of Bird Divergence and Convergence

     Bonaparte's gulls and solitary sandpipers have much in common.  Both these kinds of birds, which are members of what are regarded as shoreline families, diverged from their respective families' usual habitats and habits in treeless environments.  That departure allows them to use nesting niches to rear offspring free of competition for space and food from their respective relatives.  That divergence also makes each family more diverse, and successful.    
     While the relatives of these birds raise young on the ground in open habitats, including shores, marshes and the tundra, Bonaparte's and solitaries adapted to hatching offspring in nests high in spruce and fir trees, where they won't be bothered by ground predators, near inland lakes and rivers in the forests of Canada and Alaska.  And there they converged with each other in the same habitat that shaped them into somewhat similar creatures.       
     Unlike their relatives that power swiftly in groups in open country, Bonaparte's and solitaries both fly more buoyantly than their cousins, probably to be able to fly safely among trees with ease.  And Bonaparte's and solitaries migrate through the Mid-Atlantic States; north in spring and south during fall.  But the gulls spend northern winters along both sea coasts of the United States while the sandpipers winter in northern South American forests.
     Bonaparte's are pretty gulls in summer, with dark heads, light-gray upper wings and backs, white under parts and red legs.  They also have a broad, white stripe on each wing.  When those gulls are in flight, those white bars, from a distance, look like banners waving in the wind. 
     Bonaparte's build nurseries of twigs, grass and moss in spruce and fir trees in boreal forests.  Each female lays two to four olive or buff, and dark-spotted eggs in her cradle.  The parent gulls bring insects and small fish to the fluffy chicks in their cradles until they are ready to fly.
     Solitaries lay their four eggs in the abandoned nests of jays, thrushes and blackbirds in Canadian and Alaskan forests.  Their four eggs per clutch are pale-green or buff and spotted with gray or brown.  Soon after hatching, the young jump from their nursery to the ground below where they forage for invertebrates.         
     Solitaries are handsome birds.  They are dark on top with several light spots that mimic sunlight dappling through trees in the shadowy woods.  This is a departure from plumage colors in other sandpipers, most of which are brown or light gray for camouflage on mud and in shallow water.  And true to their name, they generally are individuals wading in shallow water after aquatic invertebrates.  That trait probably is a result of solitaries nesting in isolated pairs in dense forests where birds of any kind would have trouble navigating together in flocks.     
     Though we here in the Middle Atlantic States only see Bonaparte's and solitaries on migration, it is interesting to note how these unrelated species use similar nesting niches in the same summer environment for the safety of the youngsters.  Habitats shape the critters that live in them into similar creatures; like the shapes of fish and whales.