The flicker fusion frequency of budgerigars (Melopsittacus undulatus) revisited

Abstract

While color vision and spatial resolution have been studied in many bird species, less is known about the temporal aspects of bird vision. High temporal resolution has been described in three species of passerines but it is unknown whether this is specific to passerines, to small actively flying birds, to insectivores or to birds living in bright habitats. Temporal resolution of vision is commonly tested by determining the flicker fusion frequency (FFF), at which the eye can no longer distinguish a flickering light from a constant light of equal intensity at different luminances. Using a food reward, we trained the birds to discriminate a constant light from a flickering light, at four different luminances between 750 and 7500 cd/m². The highest FFF found in one bird at 3500 cd/m² was 93 Hz. Three birds had higher FFF (82 Hz) at 7500 cd/m² than at 3500 cd/m². Six human subjects had lower FFF than the birds at 1500 but similar FFF at 750 cd/m². These results indicate that high temporal resolution is not a common trait for all small and active birds living in bright light habitats. Whether it is typical for passerines or for insectivorous birds remains to be tested.

Keywords: Avian vision; Flicker fusion frequency; Psittaciformes; Temporal resolution; Visual ecology.

Fig. 1

The spectral distribution of the stimulus light used for the experiments

Fig. 2

a Flicker fusion frequencies of all five birds (Bud, Lucky, Bart, Pippi, Milou) in tests with four luminances. Open circles: results with low background intensities; crosses results with higher background intensities (see Table 1). b Average FFF of budgerigars. Note that the luminance scale here is logarithmic. Gray open triangles show the results obtained with two birds in experiments performed and published by Ginsburg and Nilsson (1971). Black open triangles show averages obtained with the birds (except Bud, whose data are excluded because he only cooperated in one test) tested in our study (results with low and high background luminances are given as separate points when the results were statistically different). Filled triangles show average values obtained with six human subjects under the same conditions