Range (biology)

Population distribution redirects here. For the probability distribution of a statistical population see Probability distribution and Statistical population.

The three basic types of population distribution within an area. From top to bottom: spaced (uniform/regular), random and clumped (aggregated).

In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.

The term is often qualified:

• sometimes a distinction is made between a species' native range and the places to which it has been introduced by human agency (deliberately or accidentally), as well as where it has been re-introduced following extirpation.
• for species which are found in different regions at different times of year, terms such as summer range and winter range are often employed.
• for species where only part of their range is used for breeding activity, the terms breeding range and non-breeding range are not used.
• when discussing mobile animals, the species' natural range is often discussed, as opposed to areas where it occurs as a vagrant.
• geographic or temporal qualifiers are often added e.g. British range or pre-1950 range.

There are at least five types of distribution patterns:

• scattered/random (Random placement)
• clustered/grouped (The majority are placed in one area)
• linear (Their placements form a line)
• radial (Placements form an ' x ' shape)
• Regular/ordered (They are not random at all, but follow a set placement. Much like a grid)

Bird wildlife corridors

One common example of bird species' ranges are land mass areas bordering water bodies, for example oceans, rivers, or lakes, and called a coastal strip. A second example, some species of bird depend on water, usually a river, swamp, etc., or water related forest and live in a river corridor. A separate example of a river corridor would be a river corridor that includes the entire drainage, having the edge of the range delimited by mountains, or higher elevations; the river itself would be a smaller percentage of this entire wildlife corridor, but the corridor is created because of the river.

A further example of a bird wildlife corridor would be a mountain range corridor. In the U.S. of North America, the Sierra Nevada range in the west, and the Appalachian Mountains in the east are two examples of this habitat, used in summer, and winter, by separate species, for different reasons.

Bird species in these corridors are either connected to a main range for the species, (be contiguous), or in an isolated geographic range and be a disjunct range. Birds leaving the area, if they migrate would either leave connected to the main range, or have to fly over land not connected to the wildlife corridor, and thus be passage migrants over land that they stop on for an intermittent, hit or miss, visit.

See also

• Biological dispersal
• Colonisation
• Occupancy-abundance relationship
• Species distribution