Only if he is showing any agression towards the mother or baby, or if he is trying to mate with the baby. That would be very weird.
Male guinea pigs CAN harm newborns, as they aren't fully aware of the situation. i wouldn't recommend keeping newborns with the father. They should be feeding with the mother. After 4-5 weeks the males have to be separated from the mother as they become sexually active at that age, and can impregnate the mother.
sometimes
female
you should look it up online and a whole bunch of pictures will come up.
No, I think that the male should remain in with the female to help her with the feeding of the babies.
Maybe
A male parakeet has a blue nose above its beak.
Depends on the male if it usually goes in the nest then yes
you can leave them together all the time
The female and male parakeet do a cloaca kiss and make a baby bird deedadee
NO NO NO!!! ABSOLUTELY NOT!!!!! the male will eat the newborns and you will be getting ready to go to a funeral! PLEASE put cardboard between the adult male and the female with newborns. Make sure to feed her a TINY bit extra if she is nursing. P.S. And exchange the cardboard with wood if he starts to nibble through the cardboard!!!
Presuming that 'parakeet' means budgie, even though there is actually no species known as a parakeet, the cere, which is the part above a budgies's beak where their nostrils are, is bright blue on a mature male budgie.