11. Avian Communities in Temperate Rainforests
239
Diversity of species using covered nests was higher in broadleaf than in
conifer forest , but their abundance was similar (parts A and B, Table
11.4). South temperate forests held more species of covered-nesters than
the other forests, and this guild was least abundant in northwestern
forests. Thus, midwestern forest birds of this guild had relatively fewer
species but equal proportions of individuals, as compared to south temperate forests, and equal proportions of species but more individuals, as
compared to northwestern forests. This indicates that there was a greater
average density per species in the midwestern users of covered nests.
Understory species diversity showed no significant trends with location
or forest type (part A, Table 11.4). Abundance was least in northwestern
forests, and greater in conifer than in broadleaf forests (part B, Table
11.4). Aerial feeders were least speciose and least abundant in northwestern forests, and more diverse and more abundant in broadleaf than
coniferous forests (parts A and B, Table 11.4).
Canopy seed predators were most diverse in south temperate forests,
followed by northwestern and midwestern forests (part A, Table 11.4).
Abundance patterns followed the same ranking (part B, Table 11.4).
However, the value for northwestern forests is underestimated, as discussed earlier. Furthermore, the low values for midwestern forests reflect
the extinction of two major canopy seed predators in the last century
(Ectopistes migratorius and Conuropsis carolinensis). Therefore, this
trend is spurious but serves to emphasize the point that canopy seedeaters in the Chilote forests are a noteworthy component of the avifauna.
Leaf-gleaners were least speciose and least abundant in south temperate
forests (parts A and B, Table 11.4). They were consistently (but not
significantly) more diverse in conifer than broadleaf forests, and significantly more abundant in conifer forests.
Predictions About Comparative Guild Structure
First, the architectural form of most broadleaf trees produces many large
branches, whereas that of conifers is commonly a set of relatively small
branches off the main trunk. If the difference in branching pattern is
associated with a parallel difference in availability of foraging surfaces
and cavity nest-sites, then one might predict a greater diversity or abundance of big-tree users in broadleaf forests. The linear array of the six
categories of forest (3 locations x 2 types) showed that , indeed , broadleaf
forests tend to host more species of big-tree users than conifer forests
(part A, Table 11.4), although the Tukey post-hoc test did not detect
significant differences at the predicted point in the array. In contrast,
corresponding differences in abundances were not apparent between
broadleaf and conifer forests (part B, Table 11.4). Large broadleaf trees
may offer more avenues for exploitation, but not necessarily more
resources.
239
Diversity of species using covered nests was higher in broadleaf than in
conifer forest , but their abundance was similar (parts A and B, Table
11.4). South temperate forests held more species of covered-nesters than
the other forests, and this guild was least abundant in northwestern
forests. Thus, midwestern forest birds of this guild had relatively fewer
species but equal proportions of individuals, as compared to south temperate forests, and equal proportions of species but more individuals, as
compared to northwestern forests. This indicates that there was a greater
average density per species in the midwestern users of covered nests.
Understory species diversity showed no significant trends with location
or forest type (part A, Table 11.4). Abundance was least in northwestern
forests, and greater in conifer than in broadleaf forests (part B, Table
11.4). Aerial feeders were least speciose and least abundant in northwestern forests, and more diverse and more abundant in broadleaf than
coniferous forests (parts A and B, Table 11.4).
Canopy seed predators were most diverse in south temperate forests,
followed by northwestern and midwestern forests (part A, Table 11.4).
Abundance patterns followed the same ranking (part B, Table 11.4).
However, the value for northwestern forests is underestimated, as discussed earlier. Furthermore, the low values for midwestern forests reflect
the extinction of two major canopy seed predators in the last century
(Ectopistes migratorius and Conuropsis carolinensis). Therefore, this
trend is spurious but serves to emphasize the point that canopy seedeaters in the Chilote forests are a noteworthy component of the avifauna.
Leaf-gleaners were least speciose and least abundant in south temperate
forests (parts A and B, Table 11.4). They were consistently (but not
significantly) more diverse in conifer than broadleaf forests, and significantly more abundant in conifer forests.
Predictions About Comparative Guild Structure
First, the architectural form of most broadleaf trees produces many large
branches, whereas that of conifers is commonly a set of relatively small
branches off the main trunk. If the difference in branching pattern is
associated with a parallel difference in availability of foraging surfaces
and cavity nest-sites, then one might predict a greater diversity or abundance of big-tree users in broadleaf forests. The linear array of the six
categories of forest (3 locations x 2 types) showed that , indeed , broadleaf
forests tend to host more species of big-tree users than conifer forests
(part A, Table 11.4), although the Tukey post-hoc test did not detect
significant differences at the predicted point in the array. In contrast,
corresponding differences in abundances were not apparent between
broadleaf and conifer forests (part B, Table 11.4). Large broadleaf trees
may offer more avenues for exploitation, but not necessarily more
resources.