When we had cattle the cow paths showed up in the pasture, even where there was no obvious destination (for the shortest route to explain it). Legend has it that cattle form these paths along magnetic lines.

Anyway, the veracity of that legend doesn't matter, but it is here merely to illustrate the idea that perhaps we subconsciously build our roads on lines that chickens won't cross, rather than them being aware of the road?

I spent an afternoon in a chicken farm while the owners were installing a synthetic grass football field and the chicken that were free just avoided that grass. We didn't know why, besides the fact that it didn't have any bugs in it it looked very similar to the rest of the grass