Although Jason waited a fair bit for the end of the battle, when he approached the area where he found Helena the previous day, he found her groups still fighting dozens of Flamed Avians… a lot of corpses of them were still on the ground already, so it seemed that they had been coming nonstop.
In the end, Jason could shout and ask if she wanted help, but that would reveal his position anyway and that would force him to help. It was better to just attack them from behind to end things as fast as possible. Besides, if her group complains, he has some excuses in store, like he wanted to open a path to retreat a bit, or he didn't see them, or that they were too slow. All of them sounded like he wanted to pick a fight with them, though.
Without hesitation, Jason attacked the monsters from behind and wiped them out. In the end, he finally mastered the crossbow… It took a bit longer than he had expected since he used his mana with wind magic over the night.