The morphs would have evolved into different subspecies in isolation, but rejoined into one breeding population after another geographic shift. First, it’s possible that the three different morphs are a result of vicariant evolution, a speciation tale as old as time that involves the separation-usually by environmental factors-of a population and its subsequent evolutionary branches. There are a couple hypotheses as to what scientists are currently observing in Gouldian finch behavior. gouldiae population segments are in the process of diverging. The fact that breeding between two morphs has such a powerful effect suggests that E. In most organisms, breeding between different morphs doesn’t have the same sort of negative impact on reproductive success as breeding between species. This in turn may lead to reproductive isolation and a loss of rare morphs. Although mating with like individuals tends to improve breeding success, it also negatively affects genetic diversity within a population by limiting gene flow. As a result, they have smaller broods with fewer females, the sex most adversely affected by a poor match (in line with a genetic observation known as Haldane’s rule). Studies show that females in incompatible pairings tend to produce higher levels of stress hormones. Gouldian finches also follow an assortative mating pattern, meaning that they prefer to mate with finches that look like them. The trade-off for this advantageous characteristic is a shorter life-span and decreased parental investment red-headed males are less helpful in raising young because they spend more time fighting. Interestingly, head color is the most important indicator of all and is linked closely to behavior: Red-headed finches are the most competitive and aggressive of all the morphs, usually winning access to the best nesting sites-hollows in eucalyptus trees-and food sources. Birds that have the richest diets tend to have more vibrant plumage and will therefore be more attractive to potential mates. The brightness of a bird’s coloration can provide a powerful visual indication of its fitness, and in particular, its ability to obtain food. Male and female Gouldian finches share the same distribution of colors but males are, as is common in the animal kingdom, brighter than females. The birds are still widely traded in that community, but captive populations now differ from the wild ones, having been bred for several non-natural color mutations.Ĭoloration provides a tremendous amount of information within a Gouldian finch population and plays an important role in mate selection and reproductive success. In addition, thousands of wild Gouldian finches were captured during the early 20 th century and sold to aviculture enthusiasts worldwide. Recent studies have identified several factors that may have contributed to their place on that list, including cattle grazing, invasive species (both flora and fauna), and increased prevalence of wildfires. Gouldian finches were once found in large numbers across northern Australia, spanning the Northern Territory, Western Australia, and Queensland regions, but now the largest population is found in the Kimberley, a sparsely populated area of Western Australia. There are fewer than 3,000 finches remaining in the wild, which puts them on the world’s growing list of endangered species. Color is simply the observable surface of evolutionary, genetic, and behavioral forces at work. In Gouldian finches, scientists have found that color morphs are linked to distinct behavioral characteristics, mate selection, and reproductive success, so the variations are clearly more than coincidence or luck of the genetic draw. In birds, however, consistent coloration is far more often the norm. Polymorphism, which occurs when genetic variation results in two or more “morphs” within a species, is not uncommon in nature. In wild populations, there are three possible head color variations, or “morphs”-black, yellow, and red-and how and why each bird sports a particular hue is open to plenty of debate and research. But perhaps the most interesting, and definitely the most telling, characteristic of this species is its head color. This passerine, native to northern Australia, averages just six inches long, but can count itself among the most colorful birds around, with its brilliant and distinctive blocked pattern: green wings, bright purple chest, yellow belly, and turquoise headband. For such a small bird, the Gouldian finch ( Eryhrura gouldiae) inspires a huge number of questions.
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