Chullin 141 - How To Send The Mother Bird Away
If the mother bird was flying above the nest, as long as her wings are touching the nest, he is still obligated to send her away, but if the wings are not touching, he is exempt. This is derived from the special word for sitting, "rovetzet" that the Torah used, literally, crouching.
If there were fledgling chicks in the nest or infertile eggs, he does not send the mother bird away. The chicks must be like the eggs, dependent on their mother, and the eggs like the chicks, viable. If one sent the mother bird away and she returned, he is still obligated to send her away, any number of times.
If one violated the commandment and took the mother bird, he incurs lashes, like for any negative commandment - these are the words of Rabbi Yehudah. However, the Sages say that he does not incur lashes, because of a general rule: any negative commandment , if it is followed a positive commandment can be corrected with this positive act. Here too, the Torah said, "Do not take the mother… send her away," so sending her away afterwards helps.
Art: Martin Johnson Heade - Two Ruby Throats by their Nest