Yeah, My birds are all in an aviary outdoors.  Wild birds can poop in there, grass grows inside... who knows what they might get besides worms...  
 So I treat them two times twice a year.  With 10 days interval.  First time to kill the worms, second time to kill the worms that hatched out of any possible eggs.  
I doubt your bird would catch anything while being outside for a couple of hours during summertime, but if you want to be safe rather than sorry, there's no harm in treating them for it.