Parents of many songbird chicks will stop feeding them and leave the nest if they feel there is a big predator near, and if humans handle the chicks or the nest.
It is said that psitacids attack ill members of their group to death -about this particular point I have not source- and many vets advice to separate ninfas or agapornis pairs when one of them looks ill, just to avoid the other one kills it.
Migrant bird can leave a healthy set of chicks if migration time has arrived, it has been observed in Apus apus and some other, by example in Hirundo rustica this behavior is less frequent.
But when it comes to birds and mammals every coin has two sides. They can be very compassive and even make an enormus effort to help a dying mate (1), and there have been studies that the have a notion of death and even mourning rituals (2).
(1) Difficult to believe?, take a glance to this web page:
Image: Wilson Hsu