Symposium Participants: Gary Stiles
Open Questions and Suggestions for Action
Some of the more interesting questions regarding austral migration that could be studied in the coming years are the following: Do austral migrants have specific, well-defined migration routes or “flyways” as do many boreal migrants? Do they use specific stopover sites? How constant are arrival and departure dates for austral migrants from year to year? Do austral migrants lay down fat deposits comparable to those of boreal migrants? How do their diets change before, during and after migratory periods? To what extent do specific habitats (e.g., riverine successional habitats in Amazonia) and landforms (e. g., the Andes) affect movement patterns and areas of residence? Do breeding and molt cycles show similar relations to migratory movements as in boreal migrants? Are any austral migrants threatened primarily by problems on their winter ranges?
Answering these questions will require taking a number of steps, some of which will require international cooperation among South American countries. A series of strategically located monitoring sites should be set up in each country (and where two countries meet, possible international sites could be established, as in the Leticia-Tabatinga area of Colombia-Brasil). Long-term monitoring and banding programs will be needed, which in turn will require a common data base and banding scheme for all the countries involved. To insure uniform criteria for taking data in different countries, a series of regional training workshops should be instituted. One output of such workshops might be a series of identification manuals that detail methods for distinguishing austral migrants from similar resident congeners – as mentioned above, this problem is much more severe for austral than for boreal migrants.
From my experience in observing and banding boreal migrants over many years in Costa Rica (Stiles 1994) and Colombia (and much more limited experience with austral migrants in Colombia), I venture to offer several suggestions toward implementing these steps. The monitoring sites should contain varied vegetation of different heights: though migrants must occur in forested areas (or perforce pass through them while migrating through the Amazon basis), they are much more obvious (and bandable!) in nonforest areas like savannas or second-growth scrub. Because most migrants in forest areas may be found in the canopy and thus all but impossible to see, count or capture, vegetation of the study area may require management to maintain an adequate extension of early successional growth. Young riverine succession may well constitute an important habitat for migrants in the Amazon basin, and should be included in sites to be monitored insofar as practical.
With respect to training programs, I think that it will be important to have workshops based at least initially in the source countries for austral migrants : i.e., where these species breed. This will facilitate the initial familiarization with these species by observers and banders from other countries, who can then return better prepared to distinguish them. It will be important to include museum as well as field and laboratory work, to permit learning of the different plumages of austral migrants (another advantage of source countries for such workshops, as their museums are more likely to have good series of these species). Once they are thoroughly familiar with the austral migrants, workers from other countries can prepare identification manuals for distinguishing these species from confusingly similar resident species of their respective regions. A final suggestion is that it might be more feasible to fund projects on austral migrants by combining them with others on boreal migrants (which at present are much more likely to receive funding, since the source countries for austral migrants are much less willing or able to fund such projects in other countries). In the long term, however, it seems inevitable that if we are to make significant progress in understanding austral migration, the austral countries, where these species breed, will have to take the initiative. Just as North American leadership in the study of boreal migrants has stemmed from a concern for the welfare of “their” breeding birds, so might the authorities in the austral countries become convinced of the importance of funding projects on the migration and wintering biology of “their” birds. Ultimately, a major education program to inform public servants on the importance of conservation of austral migrants, may be the best way to assure the study and conservation of these species.
Acknowledgments
I am grateful to Doug Levey, Alex Jahn and Kim Smith for the opportunity to attend this symposium, and to the National Science Foundation and the Instituto Humboldt for financial support. Andrea Morales and Diana Arzuza of Project BIOMAP helped to make available the data and María Isabel Morales of Conservation International-Colombia helped with the georeferencing and analysis. The collection of the Instituto de Ciencias Naturales provided the basic data, and I thank Jairo Sánchez and Arturo Rodríguez for curatorial assistance. Loreta Rosselli helped in the preparation of this presentation, and in many other ways.
References
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