If you hear a bird singing in the middle of the night, you\u2019re not hearing things. Northern mockingbirds have been known to sing all night long. Their cheerful \u201cplaylist\u201d is much the same as if they were singing at 2 p.m. instead of 2 a.m.What\u2019s going on? Ornithologists have found the midnight mockers are unmated males, apparently desperate to attract a female. Simply speaking, they are lonely and singing a bird world version of the blues.