I now am planting seedlings and seeds inside a tin can which has its bottom cut out. This creates a warm environment whilst providing protection from digging birds. Once the plant is established I can slide the can off the plant, or more often than not, just leave it on until the plant is ready to harvest. These cans have the extra bonus of providing a barrier to marauding slugs and snails and recycling a common material.
I have also made some very niffty bird scarer's out of Paua shells and bamboo canes. Not only do they work but they look good in the garden!

