Question

Two effect about what will happen if insect eating birds reduces

Answer 1

These insects feed on plants and leaves and destroy them. The birds that feed on the insects indirectly help in saving the plants and increase their growth

Answer 2

Insect eating birds help in maintaining a stability in the population of insects.If the number of that birds reduces, the insect populations increases abnormaly and lost its stability.There arise a struggle for resources.Due to competition many of the insects die and only the fittest will survive
This is an example of Dalton's theory of evolution