Why study austral migratory birds?
Research is urgently needed on the winter distribution and habitat use of austral migrants, many of which are very poorly known.
- Stotz et al. (1996)
Right: Swainson's Flycatcher (Myiarchus swainsoni), an austral migrant, breeds as far south as central Argentina and winters north to Venezuela and Colombia (Ridgely and Tudor 1994).
The elevated metabolic levels of birds, combined with their ability to rapidly and efficiently travel to seasonally benign environments has lead to the worldwide proliferation of avian migration. More than half of the 650 breeding species in North America, for example, are Neotropical-Nearctic migrants (i.e., species that breed north of the Tropic of Cancer and winter to its south; Rappole 1995). In northern Europe, up to 40% of the breeding avifauna is comprised of Palearctic-Paleotropical migrants (i.e., species that migrate between Europe/Eurasia and Africa; Herrera 1978).
The prevalence of migration on various continents has led to the current paradigm that migratory behavior has evolved many times for different reasons over large geographic scales. In fact, birds are practically synonymous with migration, making it often difficult to understand avian ecology without placing it within the framework of migration. The significance of bird movements is also pertinent within an evolutionary context; for example, growing evidence indicates that migration may have led to speciation (e.g., Bensch 1999).
It is also important to understand bird migration for practical reasons. In North America, our ability to identify causes for observed declines in populations of migratory species will ultimately determine the choice and effectiveness of management practices. Birds (both migratory and non-migratory) play a significant role in molding and maintaining ecosystem functions, as they are key players in many community processes. For example, they keep populations of herbivorous insects in check (Holmes et al. 1979; Marquis and Whelan 1994) provide seed dispersal services for many species of plants ( Jordano 2000), and may play an important role in spread of disease -- a process that is especially relevant in the case of migratory birds ( Rappole et al. 2000). A final benefit of studying these highly mobile creatures that typically reside in different countries in different months is the opportunity they provide to create collaborative ties among international researchers and agencies with shared interests in science and conservation.
Research on migration has been underway for centuries in Europe and North America, providing a blueprint of migration on these continents. With such a foundation, questions of a more causal nature, which permit predictions and paradigms on mechanisms regulating migration, are being formulated and pursued. In South America, however, available information on the basic pattern of migration is currently lacking or is pertinent only at the local scale. Until such basic data are gathered and analyzed, questions on the causes and mechanisms underlying austral migration can hardly be addressed. In contrast, permanent resident species in Latin America have been well-studied and conservation priorities for those birds in Latin America have been identified.
Literature Cited
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