There is a Midrash that speaks of the amazing rewards that will come to the individual who fulfills the Mitzva of שילוח הקן. This refers to sending away the mother bird, before taking its chicks or eggs.
If one did not have children, Hashem would give him children, in the merit of this Mitzva. Observing this Mitzva, hurries the coming of Mashiach and Eliyahu Hanavi.
The Avnei Ezel tries to explain why the reward is so great, for what appears to be a very trivial, and simple commandment.
He writes that the source of all evil in this world, that pertains to educating our children, and how people treat one another, comes from selfishness. An individual is not able to put aside his personal interests, for the benefit of the community.
Because of his obsession with money and honor, he may not be willing to go to the expense of giving his children, a proper Torah education. His ego causes him to be a person of strife, where he is constantly involved in conflict.
All of this comes about, because of selfishness, and not being aware that others may have more pressing needs. The Mitzva of Shiluach Haken, is a remedy for such selfishness.
The mother bird, is vulnerable to the desires of man. He could easily kill her to take her offspring. Instead, he shows compassion by sending her away. Her species will not become extinct, and she can start a family somewhere else. The conquering of selfishness is that which brings great reward, even to the extent of being given children, and bringing Eliyahu Hanavi and Mashiach.