The bird's feet are grasping the window tightly.
The bird is about to take off
Grasping the window tightly does not imply one is about to take off.
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 p1 s1 x1.(n_bird(x1) & Topic(s1,p1) & Actor(s1,x1) & a_about(s1) & exists e1 s2.(a_off(s2) & Manner(e1,s2) & Actor(e1,x1) & v_take(e1)))