Pulitzer Prize winner, purported Twitter hater and avid bird watcher (who knew?) Jonathan Franzen led a pack of New Yorkers with binoculars on a hunt for a cerulean warbler, and other species, in Central Park yesterday. (That warbler gets a shoutout in Franzen’s 2010 novel “Freedom.”) The trek was in the name of HBO’s upcoming doc “Birders: The Central Park Effect,” featuring Franzen. The author spotted a black-crowned night heron, and he also reflected on HBO’s not going ahead with a series based on his book “The Corrections” starring Ewan McGregor and Maggie Gyllenhaal. “ ‘Plug pulled’ would be a more accurate phrase,” he told us. We thought we heard distant chirping. Franzen added, “I felt most disappointed with respect to the cast . . . Chris Cooper in particular, who is truly amazing and heartbreaking to watch . . . I had looked forward to seeing him do the character going forward.” He added jokingly, “I take some satisfaction in my novel having defeated another medium.”