Come spring that clump of white birch may be a green and dervish thing -- and chatterbox of birds; then later in July and matronly of branches, may be a dreaming lullaby of finches; and later, in October, when summer goes south, may make a sere and sober farewell speech of crows . . . and later still -- like now, whatever can you say? -- with four shivering sparrows and one blue jay.