Sentence:  The migratory birds / have flown the coop / but they'll be back / with their built-in compass. / They'll come back the way / the circus does each year— / with <WSD>aerialists</WSD>, our angular / birds that loop the loop. 
Meaning of the word marked with <WSD> tags:  An acrobat performing high off the ground, defying a fall to earth, as on a trapeze or a tightrope.