Chickens have disappeared

I went to a previous world I was playing on and happened to find no chickens at all. I ended up deleting that world and creating a new survival world and still no chickens, I probably did this about 10 times with no luck.

I decided to try a creative world and there were chickens there. I even tried deleting the whole game itself and installing it again... no luck.

Currently, I'm still playing in survival with no chickens thinking that maybe some would spawn later in the game, but its been about 10-15 game days and all I'm getting are a lot of sheep and cows and very few pigs.

(I actually have v0.7.6, not v0.7.5, since v0.7.6 wasn't an option)