Other birds may be more attracted to the colors of their own plumage as those could indicate a potential mate or another bird that is surviving well. 1  Most bright colors, however, can be used to attract birds, with certain bird species being more attracted to particular shades. 1  Red and Pink: Hummingbirds. 2  Orange: Orioles, hummingbirds. 3  Yellow: Goldfinches, warblers, hummingbirds.  Blue: Bluebirds, jays.
This phenomenon is called the founder effect. The founder effect is generically a loss of genetic diversity. But specifically, it refers to limited genetic diversity that occurs when a small group of individuals from a genetically diverse population of some species migrates away and forms a new colony.
This article is a good article explaining how the founder effects affect genetic drift. An example of a bottleneck effect: Northern elephant seals have reduced genetic variation most likely due to being hunted. Hunting reduced their population size to as few as 20 individuals at the end if the 19th century.