Table 1: Results of the multiple linear models performed to test the effect of lake shape, physicochemical properties—depth, water transparency, and productivity (nitrogen and phosphorus concentration)—isolation (distance to river margin and distance to nearest lake), and habitat richness provided by marginal vegetation, on the qualitative and quantitative composition of the communities of aquatic birds. The first figures in the DF columns are the degrees of freedom of the treatment; the second, those of lakes. The analyses were performed on scores resultant from nonmetric multidimensional scaling (NMDS). See Section 2 for details.

Ecological variables Qualitative Quantitative Pillai-Trace F DF P Pillai-Trace F DF P Lake shape* 0.075 1.115 3; 41 0.354 0.034 0.483 3; 41 0.696 Lake depth 0.056 0.716 3; 36 0.549 0.239 3.779 3; 36 0.019 Lake productivity  Nitrogen 0.005 0.058 3; 36 0.981 0.100 1.335 3; 36 0.278  Phosphorus 0.091 1.199 3; 36 0.324 0.146 2.047 3; 36 0.125 Water transparency 0.216 3.306 3; 36 0.002 0.109 1.464 3; 36 0.240 Distance to river margins 0.274 4.534 3; 36 0.009 0.325 5.768 3; 36 0.003 Distance to nearest lake 0.329 5.883 3; 36 0.002 0.257 4.159 3; 36 0.013 Habitat richness* 0.394 8.890 3; 41 0.0001 0.598 20.334 3; 41 0.0001

*Lake shape and habitat richness were significantly correlated to other variables, and therefore analyzed in separate models (see Section 3 and also Figure 7).