Bird Tree. It is left so that birds can rest/roost there, safe and high above the clear cut
Clear fell logging is the type of timber extraction where all the trees are felled. Selective logging is an alternative, where only specific trees are extracted, or where a few type specimens are left to provide seed for the next generation of forest.
Your question isn't fully clear, but if you are referring to the process of division of numbers, the "number left over" is called a remainder.
Red Hill bats left and throws left.
Serve from the left, clear from the right.
I think it is called a 'Nictating Membrane'.
MLB player Koyie Hill can bat right or left (i.e. he is a switch hitter).
Left
MLB player Taylor Hill throws right.
MLB player Aaron Hill bats right.
MLB player Aaron Hill throws right.
MLB player Koyie Hill throws right.
MLB player Taylor Hill bats right.