Predicted visual sensitivity for short-wavelength light in the brood parasitic cuckoos of New Zealand

Abstract

Different lineages of birds show varying sensitivity to light in the ultraviolet (UV) wavelengths. In several avian brood parasite-host systems, UV-reflectance of the parasite eggs is important in discriminating own from foreign eggs by the hosts. In turn, for parasitic females it may be beneficial to lay eggs into host clutches where eggs more closely match the parasite's own eggs. While the visual sensitivities of numerous cuckoo- and cowbird-host species have been described, less is known about those of their respective parasites. Such sensory characterization is important for understanding the mechanisms underlying potential perceptual coevolutionary processes between hosts and parasites, as well as for better understanding each species' respective visual sensory ecology. We sequenced the short wavelength-sensitive type 1 (SWS1) opsin gene to predict the degree of UV- sensitivity in both of New Zealand's obligate parasitic cuckoo species, the Shining Cuckoo (Chalcites (Chrysococcyx) lucidus) and the Long-tailed Cuckoo (Urodynamis (Eudynamis) taitensis). We show that both species are predicted to possess SWS1 opsins with maximal sensitivity in the human-visible violet portion of the short-wavelength light spectrum, and not in the UV. Future studies should focus on the (mis)matching in host-parasite visual sensitivities with respect to host-parasite egg similarity as perceived by the avian visual system and the behavioral outcomes of foreign egg rejection.