An ecological niche is the part of the environment into which a species fits, and to which it is adapted. A shorthand definition of niche in biology is how an organism makes a living in a place.

However, the term has been used in different ways. It is not only a place but a way of life. For example, grazers, insectivores, scavengers and predators can all live their different lifestyles in the same forest. A niche can be occupied by different species in different places even though they 'earn their living' in roughly the same way. Thus the 'bird of prey eating small mammals' niche would in grasslands include the kestrel, but in an oak wood it would be filled by the tawny owl.