I have 20 birds and one usually lasts about 2 weeks. They pretty much pick it apart. Flock Blocks are supposed to supplement free rangers, but mine will get it as a treat 2-3 times a year.
Every flock is different in their reactions, I think. Mine don't seem to pay much attention to them unless we break chunks off and crush them up for them. Others report that their birds really devour them. Most commercial Flock Blocks are only about 9 or 10% protein (it's a treat, not a formulated, nutritional feed), so you don't want them devouring them, because then they are not eating the healthy stuff that helps with egg production and such. I think they get used most often in winter, to alleviate boredom.
they love them its like a treat for them and the pick it apart pretty quick. just make sure to keep it out of the weather
