Figure 1.
a) Photograph of apparatus. b) Plan view illustrating a test with a focal female or c) focal male in the central compartment. Stimulus birds were presented with four same-sex birds randomly picked from the breeding stock (open symbols) and 4 opposite-sex birds from manipulated brood sizes (♂L, ♀L = male, female from a large brood; ♂S, ♀S = male, female from small brood; filling patterns symbolize tutoring-group ID). Half-way through the 8h-testing period, stimulus birds (staying within their holding cages) were rotated 180 degrees. For new trials with a new stimulus set, the start position of stimulus categories were rotated one position clockwise (see methods).
Table 1.
Schematic view of the time course of experimental manipulations and preference tests.
Table 2.
Effects of experimental brood size of focal males and females (in separate analyses) on their association patterns with stimulus birds.
Table 3.
Comparison of focal males' and females' association patterns with stimulus birds (response variables are as in Table 2).
Figure 2.
Consistency of preferences after stimulus rotation.
Percentages of the total time (a, b) with and total number of visits (c, d) to small-brood opposite-sex stimuli before and after stimulus rotation. Trend lines are y = x and correlation values are Pearson r. *P < 0.05, ***P < 0.001.
Figure 3.
Preference for large and small brood birds by males and females from large and small broods.
Total time spent with small-brood versus large-brood opposite-sex stimuli by focal females (a) and males (b) from small and large broods. The y = x line illustrates an equal preference for birds from small and large broods: above this line birds from small brood are preferred, below birds from large broods are preferred. Smaller dots show the means±1 SEM per focal birds' brood sizes. The amount of time spent with opposite-sex birds from small broods depended on the brood size and sex of the focal birds: females from small broods spent significantly more time with males from small broods and females from large broods with males from large broods (see main text for statistical details).
Table 4.
Studies with experimental manipulations of male or female condition prior to mate preference tests in zebra finches.