The Zahor Hakadosh says that the reason is that the mother (Hashem) should look for her children. It says that it will be happening that a nest of birds will be found by you, but the problem is that it is written with an aleph when it should have been written with a heh. Similarly Yaakov Avinu tells his children that I will tell you what will happen and the end of days, again written with an aleph. Maybe, it says in the Midrash that Moshiach can be brought for three reasons where all three are related to reading or speech. Learning of mishnayos, belief and the act of bowing down showing appreciation for the good, That is Mishnayos, Krias Shma and Davening. What about if he does not want the birds or the eggs? There are three reason, protecting the species showing mercy and the above. According to the two reasons no because you are protecting the species, if you don’t take the birds or eggs and you show more mercy by leaving them with the mother.