Competition Assignment
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In the article “Interspecific Aggression and Habitat Selection by Amazonian Birds” interspecific aggression in habitat selection was demonstrated. It was shown in this article that interspecific aggression tends to “mediate patterns of spatial occupancy in a wide range of animals” (Robinson and Terborgh 1995). A concept that plays a major role in this article is interspecific territoriality. Interspecific territoriality is “when aggression serves to define or secure a breeding territory against members of another species” (Robinson and Terborgh 1995). It results from “competition between sympatric species” (Robinson and Terborgh 1995) which is demonstrated in this article between closely related Amazonian birds. In this article, the aggression that mediates interspecific territoriality has been found to be “highly directed, in the sense that any given species enforces territorial exclusivity against only one or two other species in a locality” (Robinson and Tergorgh 1995). This is demonstrated in this article by an interference mechanism which can be defined as “direct aggressive interaction between individuals competing for resources” (Erickson 2008), in this case territory.
Another mode of competition that is displayed in this article is a type of interference competition by the name of territorial competition. In this particular competition, “behavioral exclusion of others form spaces defended as territories” (Erickson 2008). This particular competition has been demonstrated throughout this article when the Amazonian birds display interspecific territoriality.
In the first phase of the research, the territories of more than 330 bird species in large census plots that encompassed the complete successional gradient were mapped (Robinson and Terborgh 1995). “Species pairs were found in over 20 genera that showed contiguous but non-overlapping territories, such that early stages of the successional gradient were occupied by one member of the pair, and later stages by the other” (Robinson and Terborgh 1995). “Other species pairs showed additional types of spatial relationship, including partially overlapping and completely overlapping territories” (Robinson and Terborgh 1995).
In this article, it was suggested that “spatial segregation of congeneric bird species on habitat gradients is commonly underpinned by interspecific territoriality mediated through directed, asymmetrical interspecific aggression” (Robinson and Terborgh 1995). Also, “aggressive asymmetry suggests a despotic model of habitat occupancy, in which the larger species occupies the more productive end of habitat gradients, and the smaller species occupies less productive habitats” (Robinson and Terborgh 1995). The pronounced successional gradients characteristic of Amazonia may explain much of the increased species richness, especially within genera of Amazonian bird communities. Therefore, the larger birds dominate the smaller ones (Robinson and Terborgh 1995).
In the article “Experimental Evidence for