The trees can be easily left or minorly pruned to develop the shape of a ladder. Use the tree itself to get on the tree. Also leaving some for the birds, I totally agree. There is so much that birds will give in return. Mental things like their cuteness and singing and practical like their manure, eating pests, or pooping of seeds of other trees that WILL sprout because they have been through the bird's digestive system. Finally, the higher a tree gets the deeper its roots go in the ground bringing up humidity and nutrients from the subsoil. So everyone please leave your saws down...Let nature thrive by the human doing less. Thank you
