Philadelphia Inquirer: The American robin, once a harbinger of spring, is now a year-round resident here, hunkering down for the winter in thickets. For years, Schuylkill Haven birder and wildlife author Scott Weidensaul used to relish seeing the first turkey vulture that would venture north of the Kittatiny Ridge come the melting snow. Now, he sees them throughout the winter. The story is much the same nationwide. Among more than 300 species that the National Audubon Society has data on going back …