SUPPORTING INFORMATION
Global patterns of specialization and coexistence in bird assemblages
Jonathan Belmaker, Cagan H. Sekercioglu and Walter Jetz
Journal of Biogeography
Appendix S1 Additional figures detailing the relationship between specialization and
species richness in the terrestrial birds of the world.
Figure S1 The range in areas used to define fine-grained assemblages in the different realms. The
boxes represent the interquartile range while the whiskers are the extreme values (unless more
than 1.5 times the interquartile range). We here consider assemblages censused from 10 to 7875
km2 (median: 488 km2) as fine-grained, with four additional assemblages with larger extent (8283
– 23,837 km2) added in noticeably underrepresented regions (two in Amazonia, one in Siberia
and one in West Africa). Assemblages area differ among realms (ANOVA: F5 = 6.5, P <0.001),
but this is attributed to slightly smaller areas in the Nearctic and no difference was detected once
this realm was excluded (F4 = 0.9, P = 0.44).
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316
100
Richness
32
Small area
Large area
0.88
0.92
0.38
Diet Specialization
0.62
0.82
Habitat Specialization
Figure S2 The richness–specialization relationship for the fine-grained global terrestrial
bird assemblages shown separately for the 30% smallest localities and the 30% largest
localities. Regression lines represent ordinary least squares regression estimates.
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Figure S3 (a) The frequency distribution of logit-transformed diet and habitat
specialization among all extant terrestrial bird species. (b-c) The geographic distribution
of assemblage skew in dietary and habitat specialization at the 12,100 km2 scale, with
negative values indicating left-skew and positive values right-skew. Skew was calculated
using the b1 method in Joanes & Gill (1998) after logit transformation.
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Figure S4 The slopes of the richness–specialization relationship of global terrestrial birds
for the 12,100 km2 scale across regression quantiles. Shaded area represents 90%
confidence intervals, while solid horizontal red line represents the slope estimated using
ordinary least squares regressions (with 90% CI represented as dashed red lines).
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Figure S5 Relative importance of species richness correlates of global terrestrial birds
expressed as relative R2 and calculated as the average contribution of each predictor over
all possible models. Error bars represent bootstrapped 95% confidence intervals (1000
iterations). Only assemblages from the top 50% residuals of a linear model relating
species richness to productivity and habitat heterogeneity were included. Diet – mean diet
specialization, Habitat – mean habitat specialization, Range – mean log10 range size, Area
– log10 fine grained assemblage area.
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Figure S6 The richness–specialization relationship for the 12,100 km2 grid shown
separately for the 50% narrow-ranged species and the 50% wide-ranged species of
terrestrial birds globally. Regression lines represent ordinary least squares regression
estimates.
REFERENCE
Joanes, D.N. & Gill, C.A. (1998) Comparing measures of sample skewness and kurtosis.
Journal of the Royal Statistical Society: Series D (The Statistician), 47, 183-189.
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