A method of comparing the numbers of species in areas covered by different periods of observation.

Abstract

The number of new species added to a checklist tends to remain constant with successive doublings of time, irrespective of the breeding status of the species. This fact can be utilised to calculate, from the number of species seen over ten days, the number that would be seen in an area over a longer period. The density of species in different areas and habitats can be compared by adjusting each total for the time spent in observing.