It should be okay. After they become adults, they may fight for real over who runs the garden, but kittens are not territorial.
If your new kitten is adopted form another family it may just be trying to get back to them or If your kitten is not adopted it may just be very frightened, do you have another cat, that cat might be bullying it to stay away or Maybe it needs to get some peace and quiet somewhere.
Nature. Simple.
Perhaps the cardinal sees herself reflected in the window and assumes it is another female cardinal trying to invade her territory.
Trying to establish dominance.
Because he was trying to defy his father way of making him feel powerless by literally interpreting the command to kill a kitten.
Most male animals will attack each other as a form of dominance or trying to protect their mate or their territory.
if its a kitten- they will kill it no matter what if it is a kid cat- it coul die from an infection from killing it adult cat take it to the vet immediately
The kitten is probably trying to tell weather this new stray is a dangour to her/him. The kitten maybe staring so that she knows where the stray is and knows she/he can run away or be ready if the stray starts to approach her/him. It coud be curiosity.
He was trying to get
You can try some squeaky toys for a recently tamed feral kitten. You can also try a scratching post to help the kitty.
Probably because his hormones are so stressed he is confused.
It doesn't have a guys part. I'm not trying to be gross by saying that, but that's the truth.