Natural Selection: http://sciencecases.lib.buffalo.edu/cs/files/widowbirds.pdf
Natural selection is when a species has a favorable genotype and the further generations have the favorable gene. A group of scientist observed Widowbirds to find mating and breeding cycles. They found that during the nonbreeding season of the Widowbirds both male and female birds have a brown color that assists them in hiding in grass and other vegetation. From this we can assume that Widowbirds with drab brown coloring had a greater chance of surviving attacks from predators, while those that did not could not survive and reproduce. to hide from predators during the nonbreeding season. We could also assume that there could have been Widowbirds that aren’t brown during nonbreeding season and we eaten because they could not camouflage.
Sexual Selection: http://sciencecases.lib.buffalo.edu/cs/files/widowbirds.pdf
Sexual selection is when females of a species favor a certain phenotype. While studying the Widowbirds, the scientist also noticed that during the breeding season the males molt and produce black feathers, and characteristic red and other colored feathers. The scientist also found that the longer the tail length, the more active nests the males have. The graph below shows the results of the the tail length in birds and the amount of active nest they have.
The reptilian ancestors of current birds have been found to have teeth. But it seems that birds without teeth have become dominant. To find what happened scientist conducted an experiment. They took a layer of cells in the mouth region of a mouse embryo and placed them in the mouth region of a developing chick embryo. Then after the chick developed, they found that within the beak of the bird they found teeth. From this we can assume that birds have the genetic material for teeth, but the gene is not active. These birds mutated a “shutdown” message that stopped the production of it’s own teeth.
Genetic Drift: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3634030/
Genetic Drift is when disasters happen to the species and a few are left to recreate the population. This causes there to be a large amount of the same alleles. The Mallee Emu-wren Stipiturus mallee is an endangered bird that lives in an area where it is prone to fire. The direct effects of large fires is population bottlenecks, serial local extinctions, and recolonization. This leads to low genetic variation. Low genetic variation means that there is a less chance of the best genes to prosper, and the species can’t evolve. These natural disasters are causing the Mallee Emu-wren to go extinct.
Gene flow is migration and mixing of two different gene pools. Monk parakeets moved from Argentina to the United States through a legal pet trade. They were considered pest in Argentina, so there was a lot of them. The species has become very common, and are growing rapidly. At first they were popular and widely purchased as pets, due to their low price and flashy personality. They were, possibly, set free by owners and now populate areas as wild birds. They seemed to grow more wild attitudes after their release. Now the University of Texas at Austin has to solve the problem of moving the snappy birds from their nest on top of telephone poles, to a bird sanctuary.