Examples of spectral sensitivities for VS and UVS birds. Normalised single cone spectral sensitivities (from left to right: SWS1, SWS2, MWS and LWS) of a VS bird (Indian Peafowl Pavo cristatus)  and a UVS bird (Eurasian Blue Tit Cyanistes caeruleus)  including the effects of ocular medium absorption. Human visible range is approximately 400-700 nm, with wavelengths shorter than 400 nm being ultraviolet.
Ödeen et al. BMC Evolutionary Biology 2011 11:313 doi:10.1186/1471-2148-11-313