Tosefta על ביצה 49:1

A male [bird] is exempt [in the commandment of] "sending away." A male pheasant -- Rabbi Eliezer deems one liable and the Sages deem one exempt. An impure bird is exempt from sending away. A bird that is crouching on top of the eggs of a different species is exempt from sending away. [If the mother bird] was standing among them (i.e., the fledglings), one is exempt from sending away. [If] she was sitting on top of them, one is liable in sending away. [If] she was hovering over them at a time that her wings were touching them, one is liable in sending away. [If] her wings were not touching them, one is exempt from sending away. [If] the fledglings are tereifah, she is exempt from sending away. [If the] eggs [are unfertilized (Hul. 140b:14)], one is exempt from sending away. [If the] fledglings are able to fly and do not need their mother, one is exempt from sending away. [If] he took the mother and he did not have enough time to take the chicks before they died, or before they became tereifot, he is exempt from sending away. [If] he took the mother and afterwards took the chicks, he is liable in sending away. [If] he took the chicks and afterwards took the mother he is exempt from sending away. [If] one person took the mother and another person took the chicks, the one who took the mother is liable. One who finds nests in pits, ditches, or caves, they are permitted as to theft but forbidden as to sending away, and if [their wings were] tied, one is liable for theft and exempt from sending away. As to pigeons of a dovecote and pigeons of an attic (Hul. 139b:6, Steinsaltz tr.), they are liable in sending away and also forbidden with regards to theft, in accordance with the ways of peace.