Describe how ecologists use the technique of sampling to estimate population size?

Ecologists can't measure the whole population so instead they measure and area say a square mile and count how many of X there are. Then for this particular region they can easily estimate the amount of X's by multiplying the total number of square miles by the number of X's they found in that 1 square mile 

The return of the wolf to yellowstone national park will probably affect the bird population to some degree, not significantly. while wolves will hunt birds when necessary, they prefer to hunt larger prey. the bird population will most likely only be affected when hunting is scarce for the wolves. birds of prey will also probably not be affected as much as other birds who spend more time on the ground hunting for food as the tend to spend more time in the air or in trees since they do not need to stay on the ground for long due to the nature of the way they hunt.