How many chickens do I need?

[kannna]

My sussex tends to leave my plants alone. She nips at the leaves and such but not enough to harm them. She's more of a scratcher on the path. I even have grass! I never had that with my Barred Rocks. They ate everything in sight.

 

[Sore Thumb Suburbanite]

They sell weeder geese (which is misleading because its usually a selection by the hatchery of all their leftovers), but most breeds will do a great job weeding, go for a lightweight or medium weight bird...american buffs and pilgrims are very quiet and their weight usually doesn't trample the plants...especially females which are lighter...plus these two breeds are less noisy.
For bugs though, I would have to go with ducks, they are incredible sentinels, they can find every snail, every worm, grub and caterpillar in my yard, and they never damage my crops, just the weeds i trained them up on... but really, they are very much more into looking for bugs than eating plants. If you get a duck, get some that won't fly off and that are light weight, indian runners may be your ticket. Indian runners owe their breed ancestory to eastern farmers who needed eggs and pest control without ruining their crop.
Word of warning though, the ducks will turn the tiniest droplet of water into a deep mud hole, so don't water your garden and then let them loose, water after (that will also help make their droppings soluable and work it into the soil). Hope this helps!
Maybe you should do a combination, one goose, 3 ducks and 2 chickens... the goose watches out for the flock and eats the weeds, the ducks eat the slimy pests and seek out others without scratching and causing damage, and the chickens get to give a thorough going over of the garden once the crops are done (plus they keep the compost pile pest free)