User:Evo moose/Barn owl

Color polymorphism
The barn owl is often used in studies that investigate how the color variation seen in their feathers relates to different characteristics and how they effect the success certain individuals have on capturing certain prey. For example, a study performed on Swedish owls discovered that owls in the more Northern regions tend to be darker colored while barn owls in the more Southern regions tend to be lighter colored. Feather color seems to be correlated with the owls diet. Being a different color would appear to help certain owls catch certain prey better.

Another study found that the plumage color of these owls is correlated with other feather attributions that helps feathers to resist abrasions and help with foraging. It would appear that the levels of melanin pigment concentration is related to the reddish body coloration for the owls, however, is not related to the the size of black spots also on the owls, the age of the owls, or their gender. The black bars found on the owls wings seems to be associated with gender, age, and vane length only. Throughout the study, females, yearlings, and owls with larger black spots as well as lighter reddish plumage appeared to have more black bars. This is important because it would appear that these bars of color help to reduce bending during flight. Owls with lighter plumage color had greater barb density than owls with reddish brown plumage. This study took its findings and concluded that the color of breast plumage is in fact correlated with the color of most feathers on these owls. The part of the study that looked at melanin pigmentation levels indicates that owls with darker reddish feathers have feathers that are better able to resist physical damage. The study hypothesized that birds with darker reddish feathers might have an advantage in areas where physical damage is greater and more likely, that populations with darker reddish feathers are better suited to exploit harsher habitats, and this characteristic might cause them to renew their feathers less often than lighter colored owls. Since the study was also looking at the black bars on the owls wings, its results supported earlier claims that longer feathers are covered in more black bars because the black bars help to reduce bending during flight. Owls that displayed larger black spots or lighter plumage also displayed more black bars, as mentioned above. This might be due to similar foraging strategies or diets, or perhaps because heavier birds tend to have larger spots or lighter plumage. Females tend to have more black bars than males. Females also tend to weigh more than males. It was hypothesized that the greater number of black bars helps to support their weight during flight since having more black bars seems to help reduce bending during flight.

A discussion about feather structure was also had. Melanin pigmentation appeared to be associated with color but not spot size or feather mass. Owls with higher barb density had heavier feathers. Barb density was not correlated with spot size, but both feather mass and spot size might be linked to the quality of the barb structure. It was theorized that owls might produce heaver feathers because these feathers are in better condition to handle harsher environments and stress factors. It was documented that owls with larger spots are more resistant to physical and biological damage therefore they may be stronger as well as heavier. These owls also tend to display more and larger black bars and contain higher levels of eumelanin pigmentation that contributes to brownish color in plumage.

Another study done by Galeotti, P., Rubolin, D., et al. also looked at the general scope of birds and concluded that the ability to be polymorphic appears to have evolved in many different bird species independently, or within separate lineages. Results from this study indicate that species that live in open as well as closed habitats, and are also active during the day and night, tend to be more polymorphic. Birds tend to live in areas where their color is better suited to blend in. Variation in light causes greater polymorphic capabilities as well. The benefits associated with light and dark activeness, habitat, and common prey seem to play a major role in color polymorphism. Different birds are going to be more successful in environments where their color set and lifestyle factors make them better predators. The results from this study support the idea that color polymorphism in birds arise from an adaptive consequence of selection. This particular study only found support of the idea of disruptive selection in which a tendency is seen to favor species that are better able to blend into environments with greater variations of light.