What is immigration in ecology?

Immigration is simply to movement of an organism to an area. For example, a bird may immigrate to a new island from another island. It is important to note that if you were to describe this differently - an organism moving from an area, then the term emigrate would apply. So the example would then be, a bird emigrated from the old island to a new island.

The concept of immigration is used particularly in the field of population ecology (the ecology of species that co-exist at the same time and place, and consist of only one species e.g. a pride of lions sharing the same habitat). Immigration is used as a factor in various mathematical approaches to create population models that indicate how populations will grow or decline.