Los Amigos;birds;vertebrates;plant-animal interactions;ecology;plants;bamboo;Guadua;behavior
I presented a framework to investigate how different habitat attributes affect habitat use and specialization by organisms, in order to explain why some habitats support more specialists than others. Key variables that influence habitat use and specialization were six attributes of the novel habitat relative to source habitat (area, accessibility, structural similarity, resource richness, stability, and biotic interactions), and three attributes of source communities from which the novel habitat may draw organisms (species richness and abundance patterns within source communities, and number of and diversity across source communities). Visualizing these interactions as multidimensional surfaces suggested that discontinuities in values for habitats offer organisms opportunities to partition the habitat spectrum. I summarized habitat associations of >700 bird species recorded in the lowland Amazonian forests of southeastern Peru. Guadua bamboo supported the highest diversity of diurnal insectivores, more specialists, and the highest percentage of specialists than other monodominant habitats (Mauritia palms, Gynerium cane and Tessaria trees). Numbers of specialists were positively correlated with habitat area at large spatial scales among habitat types and at local spatial scales among Guadua bamboo patches. Communities of bamboo specialists exhibited a nested structure correlated with patch size such that specialist species richness was positively correlated with patch size. Habitat patch size did not correlate with number of specialists across monodominant habitat types, suggesting that differences in habitat quality attributes (e.g. vegetation structure or food availability) were more important for specialists than is habitat area at this level of comparison. Each monodominant habitat was distinct compared to other monodominant habitats and diverse forests in vegetation structures (leaves, stems, and filtered light). Prior studies suggested Guadua bamboo offers insectivores abundant food resources. Foraging measures of Hemitriccus tody-tyrants (Tyrannidae) supported the hypothesis of high food availability in bamboo. I propose that high food availability combined with distinct vegetation structures across large geographic areas are critical habitat attributes causing certain Guadua bamboo users, such as Hemitriccus tody-tyrants, to transition towards specialization, despite the costs of a specialized lifestyle associated with the periodic disappearance of bamboo patches following mast flowering events.