My backyard is overgrown with weeds & vines. Some of them grow inedible (for humans) berries (seeds?). Seems to me (not 100% sure) that the birds like to eat them. Is it permitted for me to uproot them?
The prohibition not to cut down fruit trees only applies to trees that give fruit that is eaten by humans, (and according to one opinion even to animals that one is obligated to feed). From what you are describing it doesn’t sound like that is the case. Nevertheless, even a tree that doesn’t bear fruit, it should not be cut down without any purpose.
Rambam Hilchos Melachim 6-9, Arugas Habosem Y:D 120, Imrei Dovid 164, Chemdas Saul 36, Eitz Hasadeh 3-1, 13, 4-1,