What is a disadvantage of the point count method of population monitoring

A disadvantage of the point count method of population monitoring is that it is only beneficial for monitoring organisms, which are fixed in one place.  

The point count method of the population includes standing in a particular position and counting a population of animals, generally birds. The species of birds or the number of birds within a circle of a particular radius is counted.  

The radius is generally formed as big as possible in order to enhance information gathering. This kind of population monitoring can only be utilized for animals, which attain a fixed position, for example, birds thriving in a specific ecosystem.  

(B.) It only records trends in population at fixed locations in the ecosystem. Correct on PLATO

most community's take hundreds of years to become stable