How can I keep birds away from my fruit trees?

A key belief of the organic gardener is that biodiversity furthers health. The more variety a landscape has, the more sustainable it is. The organic gardener therefore works to create a system where the insects that are sometimes called pests and the pathogens that cause diseases are not eradicated, but instead are kept at manageable levels by a complex system of checks and balances within a living and vibrant ecosystem. Contrary to more 'conventional' gardening practices which often use chemical methods to kill both useful and harmful garden life forms indiscriminately, this is a holistic approach that seeks to develop an understanding of the webs of interaction between the myriad of organisms that constitute the garden fauna and flora. The organic gardener will often hold the view for example that the eradication of the creatures that are often described as pests is not only not possible, but also undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive.