Answer: Mutualism
Explanation:
Mutualism is a biological interaction, between individuals of different species, where both benefit and improve their biological fitness. Similar actions that occur between members of the same species are called cooperation. Mutualism differs from other interactions in which one species benefits at the expense of another or other species; these are cases of exploitation, such as parasitism, predation, etc.
So, mutualism is a way of life in which two species that could live independently come together permanently or sporadically and each puts in some effort for the survival of both. Generally a species that is the strongest or has the most defensive resources, is the one that protects the weakest and this one "pays" it with some skill or habit that is beneficial for the other. In this case, the buffalo in some way helps the birds to get insects to feed. And as "pay", the birds warn the buffalo when predators are nearby.
