Species diversity indices
In BC, at 97% predicted community coverage, point counts and pooled
ARUs obtained equivalent species richness (q=0) in both the alpine and
the subalpine (Fig. 1). Pooled ARUs obtained higher richness scores than
point counts in the upper montane. When species were weighted by their
frequency of occurrence in either dataset (q=1), the methods performed
equivalently in the subalpine, but pooled ARUs outperformed point counts
in the alpine and upper montane (Fig. 1). Thus 3 of 6 comparisons in BC
showed equivalent performance for the two methods and 3 indicated ARUs
were superior, particularly in the upper montane.
In BC, ARU detections were more likely to intersect with our lower
estimate of the entire community than point counts in the alpine and
subalpine (Fig. 2). In the upper montane, predicted final species
richness for both methods did not approach our lower estimate of the
entire community. On average, pooled ARUs were predicted to capture 92%
(range: 83-100%) of the entire community across all habitats. Point
counts were predicted to capture 73% (62-79%).
In Chile, at 97% predicted community coverage, point counts obtained
greater species richness (q=0) values than pooled ARUs in the subalpine
and alpine (Fig. 1). In upper montane forest, the richness obtained by
both methods was equivalent. When first order diversity (q=1) was
assessed, point counts continued to be better than pooled ARUs in
detecting species diversity, outperforming ARUs in the upper montane as
well. Thus 5 out of 6 comparisons in Chile indicated that point counts
outperformed ARUs; the sixth showed a bias toward point counts, but was
non-significant (Fig. 1).
For both methods in Chile, the predicted asymptotes of the species
accumulation curves did not approach our lower estimate of the entire
community (Fig. 2). On average, pooled ARUs were predicted to capture
58% (range: 50-68%) of the entire community across all habitats. Point
counts were predicted to capture 70% (57-78%).
In both regions, over the morning, dawn ARU counts detected lower or
equivalent richness to counts later in the morning (q=0, Fig. 1). The
only exception was in the BC alpine, where dawn counts detected more
species than counts two hours after dawn (q=0, Fig. 1). Although dawn
recordings were less rich, in Chile they detected two owl and one
nightjar species that were not detected later in the morning (seeTable S1(B) and below).