The Relationship between Population Density and Body Size: The Role of Extinction and Mobility

• Published in: Oikos 1995-06, Vol.73 (2), p.225-230
• Main Authors: Ebenman, Bo, Hendenström, Anders, Wennergren, Uno, Ekstam, Börje, Landin, Jan, Tyrberg, Tommy
• Format: Article
• Language: English
• Subjects: Aerial locomotion; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Average linear density; Aves; Biological and medical sciences; Birds; Body size; Demecology; Density; Flightless birds; Fundamental and applied biological sciences. Psychology; Mammals; Population density; Population ecology; Species; Vertebrata
• ISSN: 0030-1299; 1600-0706
• DOI: 10.2307/3545912

The relationship between abundance and body size is the subject of considerable debate in ecology. Here we present new data on the relationship between population density and body mass for flightless birds. Unlike flying birds, flightless birds (and mammals) show a strong negative relationship between population density and body mass. Density decreases as the - 1.40 power of body mass, which is significantly steeper than in flying birds. This difference is mainly due to a real absence of small species with low population densities in flightless birds. Small populations of small-bodied species may not be able to persist unless sustained by immigration. The high mobility of flying birds may allow even small local populations of small-bodied species to persist through supply of immigrants, and thus can explain the weak relationship between abundance and body size for this group compared to that of flightless birds (and mammals).