TROPICS COME NORTH

     One sunny summer afternoon, I was sitting on top of a wooded stream bank and looking down through leafy boughs to the clear-running creek below when I suddenly saw a beautiful male Baltimore oriole fly low over the water.  Looking at him from above, his brilliant, black and orange plumage pattern was exceptionally striking to me.  His bright feathering among the green foliage of summer made me think of tropical America where he, and other kinds of beautiful, summering birds about his size in southeastern Pennsylvania, and elsewhere, go to escape northern winters.  These attractive, brightly-colored birds help bring the colorful tropics north for the summer.  And I have seen them all over the years. 
     Two species each of orioles, grosbeaks and tanagers have adapted to raising young each summer in southeastern Pennsylvania's agricultural areas, and elsewhere.  By adjusting to raising young in less than ideal conditions for each kind of tropical bird, these migrant species have prospered and maintained their numbers, for the most part, in spite of human activities and encroachment.  It pays to be adaptable.   
     Males of each kind of these tropical birds are beautifully feathered, and sing, to attract females of their respective species for rearing offspring, and repelling could-be, rival males.  But females of each kind have lovely feathering that blends them into their surroundings for their safety. 
     Each species has its own niche, which reduces competition for food and nest sites in which to raise their broods.  These lovely, tropical birds, come north to rear youngsters in the northern summer, feed a variety of protein-packed invertebrates to their babies.
     Baltimore orioles commonly nest in tall trees, particularly sycamores, along streams and creeks in cow pastures.  They also rear offspring on other kinds of lone trees along country roads and farm lanes in cropland.  The pale, yellow-orange female orioles build their deeply-pouched cradles of twigs, rootlets and vines on the tips of twigs that hang over water or roadways.  Such nurseries keep young orioles relatively safe from predators.    
     Adult male orchard orioles have unique and pretty plumage patterns, being deep-rusty below and black on top.  Their mates, however, are yellowish-green, which camouflages them.  This species, like Baltimore orioles, nests in lone trees in meadows.  But orchard orioles also raise young in older orchards with bigger trees.  Females of the present species build open cup nurseries of twigs and grasses on forks of twigs.
     Orchard orioles seem reclusive and usually are difficult to spot among the trees and other plants of pastures and orchards.  But males sing sweet, warbling songs that often give away their presence.
     The attractive adult male rose-breasted grosbeaks are mostly black on top, white below and have a patch of red on their upper chests.  Their mates, however, are brown and streaked, which camouflages them around their nurseries in woodland edge shrubbery.
     Some pairs of these grosbeaks from the American tropics have adapted to nesting on the edges of woodlots that overlook farmland.  They have additional nesting sites and we humans who know where they nest have added beauties to enjoy in farmland.
     Blue grosbeaks were limited to nesting in the southern half of the United States, but are now slowly pushing farther north to hatch chicks.  The attractive adult males of this lovely species are blue with beige wing bars, but their mates are brown.  Males sing from taller vegetation in the hedgerows, and roadside wires where they are quite visible.
     Blue grosbeaks rear young in thickets of shrubbery and vines in hedgerows between fields and along country roads in cropland.  Those thickets protect the young from snooping people and most predators.       
     Scarlet tanagers are tree top birds in oak forests.  But this bird species has adapted to oak woodlots and smaller woods in farm country, much to the birds' benefit. 
     Adult male scarlet tanagers are crimson with black wings and tails, but their mates are olive in color, which is good blending among tree top foliage where they place their cradles.
     Although these tanagers can be overlooked in tree tops, there are two ways to find them.  Listen for the males' raspy songs that sound like singing from American robins that have sore throats.  And scarlet tanagers sometimes come down to farm fields to catch invertebrates, making these beautiful birds more visible to us.     
     Looking quite tropical, adult male summer tanagers are red all over, but their females are yellowish-brown.  This species has been limited to nesting in the southern United States, but is now slowly pushing north to rear offspring.  This species, like its cousin, prefers oak woods to hatch babies.
     Interestingly, summer tanagers specialize in catching bees and wasps on the wing.  They batter these insects on twigs to get rid of the stingers before consuming them.    
     All these beautiful birds escape northern winters by migrating in late summer to Central and northern South America.  But while they were nesting here in southeastern Pennsylvania, and elsewhere, they were representatives of the tropics they winter in and, probably, originated in.  They are a bit of the tropics come north.