Table 2. GLM models for the effects of ingredient, color, interaction of ingredient and color, and relative brightness on dough chosen first as well as the effect of the dough’s color on the buzzards’ visitation rate.
| Experimental identifier, treatment and data set | Independent variable | Parameter estimate | SE | Chi-square | P |
|---|---|---|---|---|---|
| 1: Ingredient (with constant color yellow) | |||||
| All events | Pollen | 1.117 | 0.529 | 4.46 | 0.035 |
| Sugar | 0.493 | 0.383 | 1.66 | 0.198 | |
| Soybean | -0.780 | 0.854 | 0.83 | 0.361 | |
| Individual-based events | Pollen | 1.723 | 0.912 | 3.57 | 0.059 |
| Sugar | -0.288 | 0.763 | 0.14 | 0.706 | |
| Soybean | -24.078 | 195372 | 0.00 | 0.999 | |
| 2: Color (with constant ingredients) | |||||
| All events | Color | N/A | N/A | 23.00 | <0.001 |
| Individual-based events | Color | N/A | N/A | 8.00 | 0.005 |
| 3: Ingredient (with constant color black) | |||||
| All events | Pollen | 0.865 | 0.422 | 4.21 | 0.040 |
| Individual-based events | Pollen | 0.693 | 0.612 | 1.28 | 0.258 |
| Relative brightness | |||||
| All events | Darker dough | -0.053 | 0.188 | 0.08 | 0.778 |
| Individual-based events | Darker dough | -0.095 | 0.309 | 0.10 | 0.758 |
| 1a & 3: Olfaction and vision interaction | |||||
| All events | Yellow | 3.258 | 1.019 | 10.22 | 0.001 |
| Black | -2.393 | 1.103 | 4.71 | 0.030 | |
| Individual-based events | Yellow | 3.258 | 1.019 | 10.22 | 0.001 |
| Black | -2.565 | 1.189 | 4.65 | 0.031 | |
| Effect of color on visitation rate | |||||
| All visits | Proportion of yellow dough | 2.402 | 0.367 | 42.89 | <0.001 |
In experiment 2, we used a standard Chi-square test (see Methods). All other Chi-square values are Wald Chi-square values as calculated by SAS 9.4. Each Chi-square test has one degree of freedom.