Research has found the wing shapes of captive orange-bellied parrots differ from their wild counterparts, suggesting a potential reason for the low survival rate upon release for the critically endangered migratory Tasmanian bird.
The paper from researchers at the Australian National University, University of Sydney and others analysed wing shape data of 201 orange-bellied parrot specimens including 147 from captive-born birds and 54 wild-born.
The parrots migrate annually from their breeding area in Tasmania's South-West to winter foraging grounds on the mainland, meaning the shape of their wings is critical for survival.
But released captive birds have a survival rate of below 20 per cent on their first migration, comparable with wild-born juvenile parrots.
That issue prompted the study, which could have wider uses for breeding programs of other endangered species worldwide.
Lead researcher Dejan Stojanovic said that released captive birds "should be as similar as possible to their wild counterparts", but wing variations developed in captivity could be a problem.
"We found that captive orange-bellied parrots have differently shaped wings to wild ones," he said.
"Counting from the leading edge of the wing, captive birds have shorter second and third feathers, but longer fifth and sixth feathers than wild birds.
"It suggests that wing shape change may be due to differences in feather development experienced in aviaries, or perhaps due to relaxed selection pressure."
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Pointed wings - found in wild orange-bellied parrots - are more beneficial for long-distance flying as they reduce drag, but limit agility. Rounded wings, like those in captive birds, are better suited to aviaries and captivity as they allow for greater agility over shorter distances.
The study suggested that the limited space for flight, the need for agility in smaller spaces, the inability to undertake sustained flight and an artificial diet could be factors in the wing differences, thus impacting migration.
"Evidence from these and other studies suggests that the combination of poor feather condition in some captive parrots and the differences in wing tip shape we discovered, may be an impediment during the physically challenging migration flights necessary for life in the wild," the research found.
Orange-bellied parrots have been bred in captivity since 1986.
The research paper hoped the results could be built upon to improve the health and viability of captive-bred migratory birds, including the orange-bellied parrot.
"Given that migration is by its nature very physically demanding, we suggest that wing shape should be considered a factor that may influence survival after release," the paper stated.
"Furthermore, a future research priority should be to evaluate whether aspects of wing shape are heritable.
"If it were, then this would provide managers with new information to assist when selecting birds for breeding. This would open a new avenue of research into what aspects of the captive environment influence feather development."