something like the fairly new 15-85mm would no doubt be better and give a wider focal range
I dont know if that lens is ideal for bird photography, but family shots sure.
If your after one zoom to leave on id be looking at either:
Canon 70-300mm is usm
Canon 100-400mm is l
Dependent upon you budget, the 100-400mm is l, is a better lens but its triple the price of the 70-300mm is usm.
However if its birds and butterflies you want to photograph if you can sacrifice zoom ability the 300mm f4 is l sounds like the right lens for you, price is midway between the two zooms and team it up with a 1.4 teleconverter and you've got a great birding outfit.