I have a lovebird, and she just laid two eggs. She is caged with a sun conure. Can she breed with another species of bird, or are her eggs unfertilized?
Breeding with another species can and often does occur. A cross of two species is called “hybridization.” However, it generally occurs with birds in the same genus.
The most common example of this is the Catalina macaw, which is a cross between a blue-and-gold macaw and a scarlet macaw; they are two different species but in the same genus. It is possible for birds of different genera to produce offspring, but it is very rare and most notably occurs in lories, lorikeets and some Australian parrots.
In the case of a lovebird, which is an Old World African parrot and a sun conure, which is a New World South American parrot, it is impossible for the eggs to be fertile.