Interesting question...
I don't know about birds, but what comes to my mind is "any native toxic plant" for them : they have an instinct for not feeding on these.
Yew, for instance : they can eat the berries, but there are rarely any on bonsai, or small-scale trees. I think birds in general prefer berries or fruit, not leaves.
Pines ans piceas are I think to avoid : blackbirds or the like in my garden love the new buds !
Not sure about maples, but I haven't seen any eaten by the local birds. On the contrary, they feed on insects like leaf-cutter-bees (or whatever their name is) and caterpillars...
And birds' droppings are a very good fertilizer in the spring