Abstract:

Nearctic avian migrants in temperate and tropical communities. Poputations of over 300 species of birds that breed in America, north of Mexico, spend a portion of their life cycle in the tropical zone. Studies in Veracruz, Mexico, and elsewhere in the tropics have shown that there is intense intraspecific competition, fidelity to wintering sites, and niche specificity in migrants using these tropical environments. These findings indicate that many migrant populations are as dependent for survival upon tropical communities as upon the temperate or boreal communities in which they breed. However, not only are these communities important to migrants; migrants are also important to the communities, affecting community ecology in a number of subtle but important ways including: pollination, fruiting seasons and dispersal strategies in plants; invertebrate hatching periods; parasite life cycles and breeding cycles among resident frugivores, insectivores and carnivores. Migratory birds from a fragile link between ecosystems thousands of kilomemeters apart. Through these species the effects of habitat misuse in one area can be felt throughout many widely separated parts of the hemisphere. The ecology of the migrant symbolizes the need for international cooperation in matters of conservation.