I did some research its part of the portal gun mod and apparently theres a way to disable it by setting the easter egg option to 0 in its config file but I think its on the server end that it needs to be changed just an option and food for thought
-Edit- yes I just modified my portal gun config set easter eggs to value 0 and it turned the chickens off so u can do it client side
c:/users/(user name)/twitch/Minecraft/instances/FTB presents Direwolf20/config/
portalgun.cnf
edit the line below set to 0
others {
# Oh wouldn't you like to know?
I:easterEgg=0
that's the line that needs to be set at 0
#Disclaimer- do so at your own risk it worked for me though
Merry x-mas everyone
