How can the extinction of bird species create a ripple effect through the rest of the ecosystem?

The population or that bird's predation will decrease in population because their food has been removed. This bird's prey will increase in population because their predator was removed. The scale of the effects is determined on how many other food sources or predators these other species have.

Then it is june the conclusion to the second sentence is just restating "if it is june then it is summer"