Your kitten was lucky you found him. You show so much concerrn for him with the questions you've asked today that it really warms my heart.
I really do think that he was starving and so his system is empty, and that will slow down the digestion process a bit. You just got him this morning, I'm sure he'll poop within the next 24 hours or so, so try not to worry : )
You have come up with a possibility. If he has not had enough to eat, then the little that he got went for nourishing the body. Kittens will usually poop shortly after eating. Kittens are known for eating, sleeping, playing and pooping. Once he is well-fed you may notice him pooping more. Right now, however, he may get constipated from having enough food. Every time he eats, place him in the litter box so he knows where to do to poop.
One thing that I experienced with a cat that my daughter brought me from the vet office where she worked, and one that I found - they were both constipated- and they cried a lot, and I mean A LOT. My daughter had left message on my phone that she was bringing me this kitten, and you could hear him crying in the background. She brought me two syringes full of stuff to give him an enema - and once he had those, and a bowel movement, he was okay, and never had a peep from him after that. (Poop was hard and a lot of it -like he had not pooped in a long time - his sides were distended from the buildup).
For the kitten which I just found, I used a swab to insert sweet oil into the rectum (to help ease the poop out) then used warm wet cloths to rub his bottom like the mom might do in bathing, and it helped him to poop. Apparently he was so used to mommy and would not go himself. He had been crying for a while until I realized that he needed to poop, as he had no problem peeing.
Try rubbing his bottom with wet warm cloth to see if this will help kitty. Be close to litter box or toilet so it falls in there.
Every time you squeeze it. :)
He is probably all freaked out. Keep putting him in the tray. He doesn't know where it is and he is just a baby. Aww, kitten poops!
Cats usually poop once a day. If the previous owner wasn't feeding him properly, it might take a day or so. The cat needs to have food in its system before a BM happens. Don't worry.
If he was starved, his digestive system is empty, and therefore his colon is empty. You'll have to wait until his body digests the food you've given him.
I wouldn't worry. Feed him well and he'll soon gain some weight and poo repeatedly!