Right after Han Sen's team arrived with the Ice Blue Knights, they were given a priority task to exterminate the xenogeneics that could be found around the base.
The base had been established there for some time, but xenogeneics emerged constantly from the mountains. Those xenogeneic hordes frequently caused trouble for the base.
Han Sen's mission was to venture into those mountains and clear the creatures out. There were many bird xenogeneics there, and they bred quickly. Han Sen had to wipe out their homes and destroy whatever eggs he could find. If he didn't, it'd only be a matter of time before they returned.
...
In the midst of those mountains, Han Sen was shelling a few boiled bird eggs. He ate them and frowned.