The bird's feet are grasping the window tightly.
The window is closed and has no sill
The bird can't tightly grasp a window if it is closed and has no sill.
exists e1 s1 x1 x2 x3.(n_window(x3) & n_foot(x2) & of(x2,x1) & n_bird(x1) & a_tightly(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x2) & v_grasp(e1))
exists s1 x1.(n_window(x1) & -exists e1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_have(e1) & n_sill(x2)) & Theme(s1,x1) & a_closed(s1))