Breeding in captivity can change the shape of birds’ wings, making migratory flights less likely to survive when released into the wild, new research suggests.
A study of the critically endangered orange-bellied parrot found that among captive-bred birds, those with altered wing shape had a 2.7 times lower survival rate than those born with wings closer to the ideal “wild-type” wing.
The total population of orange-bellied parrots was once as low as 17 in the wild, but their numbers have been boosted by captive breeding and release efforts in Tasmania and Victoria.
The bird breeds in Tasmania and migrates to the south coast of mainland Australia for the winter.
Study author Dr Dejan Stojanovic of the Australian National University said there was a natural variation in wing length between wild and captive-bred orange-bellied parrots.
“When you look at the length of all the feathers in a wing, there is a significant difference in the length of feathers in wild wings and captive wings,” he said.
Stojanovic has previously shown that captive-bred orange-bellied parrots have less pointed and shorter wings than their wild counterparts.
“There is variation within captivity from everything from a perfect wild type [wing] Very suboptimal,” he said.
In captive-bred birds whose wings were closest to ideal wild wings—and which were more likely to survive—the feather, known as the distal primary flight feather, was a millimeter longer.
“Literally the change for an orange-bellied parrot is a 1mm difference in the length of one feather,” Stojanovic said. “It’s very easy to detect, but it has this major downstream consequence.
“Few other recovery projects have the scale and resourcing of orange-bellied parrots.
“Despite all that care, these changes occurred and were not detected until now. These results also show that these undetected changes were having an impact on survival—a key success measure of whether we are benefiting wild populations.”
Stojanovic also analyzed the wings of 16 other birds, finding evidence of captive wing shape changes in four other species – budgerigars, turquoise parrots, sundown parrots and Gouldian finches.
“Obviously what this shows is that this phenomenon is very widespread … and may actually be one. [pattern] That was undetected,” he said. “The next step is to understand what it is that is actually driving these changes.
“Maybe it’s a family trait, or a trait of the environment … we don’t really know.”
“We need to be generally better at examining the quality of the animals we’re breeding, rather than focusing on their quantity.”
The research was published in the journal Ecology papers.