My first thought is chickens were there first, tell him the Springer has to go.
Who's house is it? Yours or your parents? If its your parents, they need to help artbitrate this situation.
That said, as other noted, Springers are bred to hunt birds.
Versus say a lab, which is bred to retrieve or a sheepdog which is bred to herd. Or a pitbull, which is bred to be loyal and protect its pack or hunt larger prey, not birds.
Most Springers will never get along with chickens.
Short of shock collar conditioning, which might work, you either have to secure the chickens or secure the dog or find one or the other a new home.