Exploring the visual system of the black grouse (Lyrurus tetrix): combining experimental and molecular approaches to inform strategies for reducing collisions.

Understanding the visual systems of birds can inform conservation efforts and mitigate the impact of collisions with human-made structures. Here, we investigated the visual abilities of the black grouse, Lyrurus tetrix (Galliformes: Phasianidae), a European mountain bird highly vulnerable to collisions with aerial infrastructures. We show that black grouse have wide monocular lateral visual fields, extensive binocular overlap and a minimal blind area behind the head, altogether indicating the ability to detect aerial objects from different fields of view. The spatial resolution and contrast sensitivity of the black grouse are in the low avian range but align with the ecology of a prey species and allow the establishment of the limits of detection of an object size and contrast under variable environmental conditions. To characterize the range of wavelengths perceived, the four cone visual pigments (SWS1, SWS2, Rh2 and LW) were reconstituted and characterized functionally, showing detection of light across a spectral range spanning the visible spectrum up to 650 nm and with limited sensitivity below 400 nm. Combined with spectral and achromatic modelling analyses, our results inform on the limits of detection of aerial objects and the perception of existing visual markers that are currently employed to mitigate black grouse collisions.