Its population periodically irrupts in cyclical outbreaks. Though often a permanent resident, it regularly irrupts further south if its food supply fails. The estuary is home to the Cameroon ghost shrimp, which periodically irrupts into dense swarms. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. This crossbill is mainly resident, but often irrupts south when its food source fails.