Yes they can because the catalyst does not take part in the chemical reaction and remains unchanged after the reaction has ended. Biological catalysts are known to be recycled by the bodies in which they work.
In this question, there are no options given to choose from. So i would answer this question based on my knowledge. The most likely cause of the observed variation is adaptation and evolution. The birds of that island adapted to the food source and then they evolved as per the requirement of the place and food source.