23 - Invasions in the mediterranean avifaunas of California and Chile

Summary

Avian biogeographers often ignore the introduced faunal element in their studies of local or regional avifaunas. They usually analyse the native species of a given fauna and pay little or no attention to the non-native element. This tradition is more noticeable in analyses of continental avifaunas than in insular ones. Such a difference in treatment is because of the fact that many insular avifaunas (Mayr, 1965; Wodzicki, 1965) have a very large component of introduced species (both in terms of species numbers and relative abundance of individuals in some species), whereas continental avifaunas have fewer (Mayr, 1965; Navas, 1987).

This chapter will describe and analyse the introduced species occurring in the continental avifaunas living in the mediterranean bioclimatic zones of California and Chile. To the author's knowledge this analysis is the first attempt to census introduced species in these avifaunas and to make biogeographic comparisons between them. Mooney et al. (1986), paraphrasing Small (1974), discussed very briefly the introduced bird species established in California, but did not focus on birds of the mediterranean-climate zone of that state. I know of no paper which reviews the introduced species of birds found in Chile. Navas (1987) discussed the nine introduced species of birds occurring in Argentina.

Introduced species found in a given avifauna can be classified in three categories:

<Tb>1. Species that were deliberately introduced by humans (‘introduced’ in the strict sense)

<Tb>2. Species that were released accidentally, e.g. caged birds kept in zoos or as pets that escaped from confinement (called ‘escapees’)

<Tb>3. Species that invaded the fauna being studied without deliberate human help during a process of natural range expansion (called ‘expanding’).