Ecological Niche

There are many factors which are important to the survival and success of a species. For instance, a quail can tolerate ambient temperatures in midsummer between 30-45°C. It eats seeds that range in size from 1-18 mm. The elevation of the habitat in which it is found ranges from 0-30 cm above the ground. Although quail are found throughout each of these ranges, they are found more often in some parts than in others. Combining all the factors that are relevant to the well-being of the quail produces a 3-dimensional "space" in the habitat that defines the niche of the species. Additional factors can be included in the description of the ecological niche of the quail, but not more than three dimensions can be graphically represented. If no other species in the same guild are present in the same habitat, this graph represents the quail's fundamental niche. If another species that utilizes the same resource is present in the same habitat, then the two species will overlap in the use of the shared resource. If there is enough separation of the two niches along the resource axis, there may be enough resources for each species to coexist together in this habitat. Then, it is likely that each species will occupy a realized niche somewhat more restricted in size than its fundamental niche. On the other hand, if the overlap is too great for the species to share the resources, then they will compete until one of the species ultimately goes extinct in the habitat. The similarity in the use of resources beyond which competitive exclusion occurs is the limiting similarity.

Adapted from: Wiens, John A. 1989. The Ecology of Bird Communities. Volume 1. Foundations and Patterns. Cambridge University Press, NY. Ricklefs, Robert E., and Gary L. Miller. 2000. Ecology. Fourth Edition. W. H. Freeman & Company, NY