Figure 1.

Proposed and tested structural relationship between predictors of species extinction risk in birds (within-family, 8664 species) with rods representing postulated causal relationships and bubbles variables. Binary extinction risk is the main response, encroachment and range size are the secondary responses in the SEM. Encroachment measures the proportion of range size modified by humans. Life history, ecological niche (eco-niche), niche breadth and environmental niche (env-niche) are latent variables (blue) which each have several hypothesized correlates (black). Selected correlates influence bird extinction risk, population decline or sensitivity to habitat modification. Thickness of all non-grey rods increases with their relative importance. Oval labels give significant standardized partial regression coefficient. Faded bubbles and rods indicate originally hypothesized but insignificant (p > 0.05) indicators and relationships, which were excluded from the final SEM. See electronic supplementary material, table S1 for abbreviations and details.