Any factor that can control a local population has a space distribution. Examples of such factors are food, nesting sites, and predators. Thus all populations are limited by the amount of suitable space. The qieaning of "suitable" for a given species is the intetesting problem. Within a given environment each necessary activity requires a
certain amount of space. That activity which requires the greatest amount of space is likely to be limiting. Thus, animals such as barnacles which wait for moving food to pass by and require very little space to catch it are likely to be limited by amount of surface on which to rest.Here "suitable space" means "space adequate for barnacle attachment." Similarly, for some insects the suitable space may be the space with sufficient food supply within easy dispersal distance; for some birds, suitable nest holes may be scarcer than adequate food and suitable space will mean proper nest hole. This section will be devoted to the nature of suitable space for the five species of warbler under consideration.