Note: You won't find angry mother cassowaries in forests where cassowaries don't tend to be.
You see it's a complicated logic. The male cassowary tends to eat the female's eggs, it's an evolutive trait that has developed over time. Therefoer females tend to go in forests outside of the typical cassowary-forests to lay the eggs far away from the males, then they go back to their natural habitat. So you can find the cassowary moms in the cassowary forest, but their eggs are in fact spread out all over the differents forests of the island.