INTRODUCTION

In many respects biodiversity, both present and past, is better understood for birds than for any other major group of organisms. This is because birds probably inspire more extreme interest in humans than all other animals (and most plants): they are often spectacular, are relatively easily observed and are usually neither too specious nor too cryptic to identify or study. Ironically, by being desirable to the collector and enigmatic and tractable to both the hobbyist and scientist, birds have helped us to document the effects of anthropogenic interference on the Earth's biodiversity during the last few hundred years in the most extraordinary detail. In birds, we benefit from an extremely rich history of scientific study, from much research of high quality in the modern era and from an enviable, though chequered, track record in conservation management. It is, however, abundantly clear that our ability to synthesise and utilise this level of knowledge will be sorely tested in the near future as we attempt to guide many avian populations through the profound environmental and biological changes that are taking place now and that will intensify in the future.

In this chapter, I will attempt to describe avian biological diversity not in the details of individual species, their distributions, status and ecological requirements, but in the context of the evolutionary history that has led to the roughly 9,000 species we have today and the broad patterns of avian diversity that we currently observe, from communities to individuals.