Introducing new stock into existing brood

[ksparks]

We had 4 chicken for a year, then we purchased 2 new chicken (14 weeks old) slowly. Neighbor dog got one of the new chickens, leaving one younger chicken alone. One of the older chickens is aggressive and attacks the younger one all the time. How long can we expect this sort of behavior from the older chicken? Is there anything we can do to alleviate the stress on the younger chicken?

 

[Den in Penn]

Welcome to BYC.
Provide hiding places. Break up the lines of sight so the aggressive one can't see the younger one so much. Distractions to keep them occupied. It is tough to introduce one new chicken to a flock, as you are finding out.