Table 1.

Results of a simultaneous autoregressive (SAR) model explaining extinction rates of breeding birds in Catalonia

Variable	t	P
Constant	1.95	0.052
x	−2.372	0.018
y	−1.942	0.053
x2	−0.983	0.326
xy	2.352	0.019
E2	−1.47	0.143
T2	2.08	0.038
ΔSE	−11.82	<0.001
H	3.123	0.002

Results of a SAR model for the effect of altitude range (H), the difference in sampling effort between the two periods (ΔSE), geographical coordinates (x, y, x², y², xy), mean absolute elevation (E), mean annual temperature (T), mean annual rainfall (R), and their squared values (E², T², and R²) on extinction rates of breeding birds in Catalonia. See ref. 2 for calculation of the environmental variables. Variables shown are those selected by the best model from all possible combinations of the independent variables using the Akaike information criterion. Accounting for spatial autocorrelation in the data using a binary connectivity matrix with a threshold distance of 30 km improved R² from 0.453 to 0.579. Note the significant positive effect of altitude range on extinction risk, even when the effect of sampling effort is included in the analysis. Ordinary least squares: R² = 0.453; SAR: R² = 0.579.