The sign indicates a marker for The Arlington Line.
A bird sits on the sign.
Birds do not always sits on a sign.
exists e1 x1 x2 x3 x4.(ne_org_line(x3) & (x3 = x4) & ne_org_arlington(x4) & n_sign(x1) & Theme(e1,x2) & Actor(e1,x1) & v_indicate(e1) & for(x2,x3) & n_marker(x2))
exists e1 x1 x2.(n_sign(x2) & on(e1,x2) & Actor(e1,x1) & v_sit(e1) & n_bird(x1))