In ecology when would you use sampling as a opposed to mark and recapture?

Question

In ecology when would you use sampling as a opposed to mark and recapture?

Answer 1

If your species doesn't move around.

If you are pretty certain that there is homogeneity in the environment.  For example, if you know that the density of your species is similar throughout your area, you can subsample and extrapolate.

Answer 2

if you do not have enough time or if your sampling plants b/c they dont migrate.  

Answer 3

You would use sampling if you are interested in the population in an area at a certain time (ex. are there more herons during the spring or during the winter).

Sampling might also be preferred if the organism that you are sampling is moving and might not return for recapture for a prohibitively long time.  

An extremely large and mobile population might also make recapturing difficult and thus favor sampling.