BIRD ASSEMBLAGES IN TEMPERATE FORESTS OF NORTH-AMERICA AND SOUTH-AMERICA - A COMPARISON OF DIVERSITY, DYNAMICS, GUILD STRUCTURE, AND RESOURCE USE
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1991
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Abstract
Using available data on entire bird assemblages of temperate forests in North and South America, we compare ecological patterns and dynamics between continents and suggest a comprehensive but low-cost research program to fill some of the many conspicuous gaps in the present state of knowledge. The scanty data available for comparison suggest that ecological trends of avifaunas are reasonably similar between grossly similar forest types on the two continents, but that important dissimilarities also occur due to different phylogenies, geologic histories, compositions of vegetation, and climate. For example, fruits apparently provide a steadier resource base in South America than in North America, whereas masting seed-, nut-, and cone-bearing trees, and "masting" insect larvae seem more prevalent in North than in South America. Accordingly, the South American avifaunas studied to date contain substantial proportions of frugivores or frugivore-insectivores, whereas North American avifaunas appear to contain larger numbers of opportunistic species and/or seed-, nut-, and cone-feeding species. We propose that North American temperate forests are more heterogeneous, seasonal, dynamic, and irruptive than their South American counterparts, from a bird's eye view. The consequence could be that South American avifaunas are less opportunistic than their North American counterparts in response to spatiotemporal heterogeneity in resources or community structure; that is, they migrate less over short and long distances. Nevertheless, data are not available to test this assertion. We propose a careful comparative study of avifaunas in evergreen and nearby deciduous forests on both continents.
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AVIFAUNA, AVIFAUNAL DYNAMICS, GUILD STRUCTURE, RESOURCE USE, MIGRATION, INTERCONTINENTAL COMPARISON, SEASONALITY, UNITED-STATES, CHILE, ARGENTINA