the shelter is not wide enough to count. eggs detection radius is alot more fine tuned than the player characters. same for the range of the fire.

also : where are the hens that make more eggs on that farm?

and third : any bat raid will have a field day with this chicken "farm" any non sheltered farm with openings or windows will get wiped clean by a bat raid in seconds. so either dont kill bonemass in that world or make sure they are fully locked away.