ABSTRACT
This chapter begins with an examination of bird structure and Archosaurian affinities. Is their relationship with theropod dinosaurs as most paleontologists contend or was their origin earlier? The origin of avian flight is central to this debate. Modern birds arose on the heels of two Cretaceous lineages, neither of which survived the end of the Mesozoic. Today, 18 Orders of birds have representatives in Southern California. Passerine birds dominate avian species diversity, and the possible reasons for that are explored.
Birds are variable in numerous ways, yet all must obey certain principles of physics if they are to fly, regardless of how they do it. Wing loading and aspect ratio are among the important factors. Birds are bipedal by default, and there is a strong correlation between hind limb structure and lifestyle.
Birds are the most visually dependent of all vertebrates, with auditory reception second in importance to sight. A sense of smell is well-developed in a few birds but hardly at all in most.
Reproduction and development is a lengthy topic covering courtship to parental care. Feeding, foraging, and dietary preferences is another comprehensive subject.
Around 40% of birds in the Northern Hemisphere migrate. Migration requires stamina and an ability to navigate. Both of these requisites are fairly well understood, but why birds migrate, or not, is an ongoing area of research.
The chapter concludes with a primer on how to identify birds in the field. For the beginner, the field guide alone is not enough.
