How does secondary succession differ from primary succession gradpoint?

Secondary succession is when a forest fire or when people chop down trees, the ecosystem still has plants there and it regrows itself.

Primary succession is when a volcano erupts of a glacier wipes out all the snow and lichen (pioneer species) grows. 

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.