In ecology, the term “niche” describes the role an organism plays in a community. A species’ niche encompasses both the physical and environmental conditions it requires (like temperature or terrain) and the interactions it has with other species (like predation or competition).

For example, the rare Kirtland’s warbler (Setophaga kirtlandii), a small songbird of North America, has a very limited niche. It nests only among young jack pine trees (Pinus banksiana), which require periodic wildfires for their seeds to germinate. In this environment, one of the species interactions it must contend with is nest parasitism by the brown-headed cowbird (Molothrus ater). Cowbirds lay their eggs in nests built by other bird species and these host birds then incubate and raise the cowbird’s young, often at the expense of their own babies.

In general, species that have narrow or limited niches are considered to be specialist species. Koalas (Phascolarctos cinereus), which feed only on leaves from eucalyptus trees in Australia, are an example of a specialist species. Species with broader niches, like coyotes (Canis latrans) or raccoons (Procyon lotor), are considered generalists. No two species can have the exact same niche, otherwise they would be in direct competition for resources with one another. If this occurs, then one species will outcompete the other. If the losing species then does not adapt, it would lead to its extinction.

Joseph Grinnell, an American ecologist, was the first person to develop the idea of an ecological niche. His definition, which he wrote about in scientific papers starting in 1917, focused on the environmental factors that determined where a species could survive rather than interactions between species. Around the same time, an English ecologist named Charles Elton was developing his own ideas about niches. In his definition, a species’ niche was determined by its interactions with other species—namely its relationships with food and predators.

Almost 40 years later, in the late 1950s, English ecologist G. Evelyn Hutchinson blended these two versions into a broader definition. This definition considers all abiotic and biotic factors that influence a species in a quantifiable way. This definition is still used by scientists today. It is important to keep learning about species’ niches today, because it can help us understand how organisms will respond to environmental changes caused by humans.