Welcome to the world of lovebirds! In a cage kept indoors, if
you keep more than two lovebirds to a cage, this is often what
happens. when they are tiny babies they are fine together, but
as they are maturing, they start to get feisty towards each
other..even if they are a sweet cuddlebug to humans, and will
compete for mates and/or nesting sites. they dont care if they
are brother/ sister parent/child..to them the siblings are
just another bird. and will kill each other to get rid of the
competition. often 1 pair will become the dominant pair... and
the rest will be killed to get rid of the competition. unless
you want more killed separate them so there are no more than 2
in 1 cage.
I learnt this the hard way, just as you are, i thought my cats
had somehow got to them, until i saw the second one being
killed, and i immediately separated them into twos. i have had
no problems since.
The first one to be killed happened overnight, when i got up
in the morning and found it the beak was missing, there was a
massive hole in the chest and one eye had been popped.