I get upset when they dig up freshly planted seedlings or eat my lettuces, so after much previous heartache, where they've ruined a bed of newly planted seedlings (raised from seed), I have learned!! Nothing gets planted without adequate protection. My garden is draped with enviromesh, netting and I make use of lots of chicken wire.
Heavy mulch in the herb garden.
Enviromesh is wonderful stuff for the organic gardener! It not only keeps the chickens off the vegetable beds, but also cats, dogs and birds. It is designed to keep insects off (such as the cabbage butterfly), while allowing light, wind and rain through. Unfortunately I don't think one can get it in SA - I've always bought mine in the UK. Once you have it, it lasts for years and years. I also bought fine green netting this year (also in the UK) to drape over my youngberries. It has also been employed to keep the chickens off certain beds which I had covered with straw - and they were most determined to scratch that off!!
Another way of protecting my newly planted seedlings and small plants is by placing slate or bricks on either side. The chickens like moist areas and tend to go straight for where one has just watered the new plant. So the garden is dotted with stones and slate or bricks which not only keep the plants in place, but also trap the moisture for the plants and give them a better chance of getting established.
Before I had chickens it was quite easy to collect a bucket full of snails at a time in my garden. Now it is difficult to find one. They do their best work eating slug and snail eggs, but will eat small snails and even big ones, when there is an insect shortage. As I've said before they are good at catching mice too! This does force me to keep my mind on the delicious egg at breakfast time, and NOT how it was produced!!