We have around 6 people in raid that have chickens and regularly use them. We’ve had bosses with 5 chickens up at a time, summoned in different ways (before/during/near boss). We’ve done this most of Classic. I’ve gotten like 2 squawk buffs. We basically all just gave up.
It seems like less than 5% likely to work, if not way lower than that.
I don’t recall it working so ineffectively in vanilla