title: Stimulus motion improves spatial contrast sensitivity in budgerigars (Melopsittacus undulatus).
abstract: Birds are generally thought to have excellent vision with high spatial resolution. However, spatial contrast sensitivity of birds for stationary targets is low compared to other animals with similar acuity, such as mammals. For fast flying animals body stability and coordination are highly important, and visual motion cues are known to be relevant for flight control. We have tested five budgerigars (Melopsittacus undulatus) in behavioural discrimination experiments to determine whether or not stimulus motion improves contrast sensitivity. The birds were trained to distinguish between a homogenous grey field and sine-wave gratings of spatial frequencies between 0.48 and 6.5 cyc/deg, and Michelson contrasts between 0.7% and 99%. The gratings were either stationary or drifting with velocities between 0.9 and 13 deg/s. Budgerigars were able to discriminate patterns of lower contrast from grey when the gratings were drifting, and the improvement in sensitivity was strongest at lower spatial frequencies and higher drift velocities. Our findings indicate that motion cues can have positive effects on visual perception of birds. This is similar to earlier results on human vision. Contrast sensitivity, tested solely with stationary stimuli, underestimates the sensory capacity of budgerigars flying through their natural environments.
authors: Institut für Zoologie, Stiftung Tierärztliche Hochschule Hannover, Germany; Department of Biology, Lund University, Sweden.
authors: Nicola Kristin
authors: NK
authors: Haller
authors: Department of Optometry and Vision Science, University of Auckland, New Zealand.
authors: Olle
authors: O
authors: Lind
authors: Institut für Zoologie, Stiftung Tierärztliche Hochschule Hannover, Germany.
authors: Stephan
authors: S
authors: Steinlechner
authors: Department of Biology, Lund University, Sweden. Electronic address: almut.kelber@biol.lu.se.
authors: Almut
authors: A
authors: Kelber
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D008297:Male; D046408:Melopsittacus / Q000502:physiology*; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology; D013028:Space Perception / Q000502:physiology*
keywords: Bird vision; Budgerigar; Motion perception; Motion vision; Spatial contrast sensitivity