Avian Visual Models In Birds And Ultraviolet Birds

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A debated topic that I did not include in my analysis included avian visual models. Birds have been shown to see in ultraviolet light (300-400nm), which humans are blind to (Cuthill et al. 2000). Birds have four cone types, while humans only have three, and so likely see the intensity of colours differently (Chen & Goldsmith, 1986; Goldsmith, 1991). They also have light-absorbing oil droplets in their cone cells, which is likely to reduce the overlap between cone sensitivities (Bowmaker et al. 1997; Vorobyev, 2003). From this, studies have found that there are two types of colour vision in birds, VS and UVS. Both vision models see in ultraviolet light, however UVS sees more towards the shorter wavelengths while VS sees towards the longer …show more content…

For example, a study by Hastad et al. (2004) showed that avian predators in raptors and Corvida have a VS colour system compared to their passerine prey with a UVS colour system. They showed that with this difference in avian vision, passerine species were conspicuous to conspecifics but less conspicuous to their predators. This has implications particularly for species of open nests; for example, brightly monochromatic open nesters may appear duller to their predators than humans perceive, resulting in less selection pressure from nest predation to become cryptic. Expanding this research using avian visual models to understand how conspecifics view each other as well as how avian predators view their prey could reveal underlying or hidden patterns that maybe weaker when only considering human perception. This could be a useful direction to take this research in as it may strengthen or weaken existing evidence for the evolution of plumage dichromatism.
The way in which I scored plumage dichromatism may also be criticised. I scored levels of dichromatism encompassing both male and female forms. However, as previously stated, sexual dichromatism has evolved through differing selection acting on both males and females, and so both males and females have encountered different changes in coloration (Hofmann et al. 2008; Price & Birch, 1996; Price & Eaton, 2014; Owens & Hartley, 1997). A combined

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