Poisoned chicken feathers helped rainbow birds to escape from parasites

Chicken feathers are treated with insecticides that can protect Tasmanian rainbow birds from the larvae of parasitic flies. When Australian ornithologists have provided the representatives of this endangered species access to poisoned nesting material, the number of parasites in their nests declined markedly. As a result, the survival rate of Chicks has increased from eight to ninety-five percent. As noted in an article for the journal of Animal Conservation, the main advantages of this technique are simplicity and low cost, and it can be adapted for other rare species.

Usually the parasites do not have a major impact on the number of hosts, but to this rule there are exceptions. For example, when the parasite penetrates into new territory, he may seriously reduce the population unsuitable to his views. This is what happened on the Galapagos Islands: there is a parasitic fly Philornis downsi, accidentally introduced by people from South America, has put many native species of passerine birds to the brink of extinction.

Tasmanian rainbow bird (Pardalotus quadragintus) has faced a similar problem. These representatives pygmy once lived at Tasmania, however, the destruction of forests promovideo of eucalyptus (Eucalyptus viminalis) and the appearance of introduced predators has resulted in a reduction of habitat and falling numbers of this species up to 1000-1500 individuals. Most of them nest on two islets off the Southeast coast of Tasmania.

Chicks in nests of rainbow birds often attacked by the larvae of flies Passeromyia longicornis, which make their way under the skin of hosts and sucking their blood. Like the owners, they are endemic to Tasmania. Apparently, the rainbow birds and the flies have coexisted for thousands of years, however, when the number of owners has decreased to a critical level, the parasites have become a deadly threat to the future of this species. Scientists estimate that P. longicornis infect up to 87 percent of the nests of iridescent birds and reduce reproductive success by 81%.

A team of ornithologists led by Fernanda Alves (Fernanda Alves) from the Australian national University decided to see if we can help the Tasmanian rainbow birds to cope with deadly parasites. Previous studies have shown that treatment of nests with insecticides during the week before hatching of Chicks reduces the number of parasites. Unfortunately, rainbow birds nest in small hollows high above the ground, and getting there is not easy.

The researchers had to look for an alternative solution. Iridescent birds build nests from grass, twigs and feathers, so the scientists had the idea to offer them chicken feathers treated with insecticides. If the bird uses them as material for their nests, it will protect the Chicks from parasites. A similar technique has worked well in the Galapagos Islands, but there not birds provided the feathers, and processed wool.

To test the effectiveness of the method, ornithologists conducted a field experiment. During two breeding seasons in 2017 and 2018, they placed a pipette with sterilized chicken feathers in the breeding sites of the iridescent birds in the North of bruny island. Birds on control sites receiving the regular feathers, and the experimental — treated with insecticide. For the purity of the experience dispensers swaps between the first and second clutches and between seasons.

Rainbow birds from the studied population nesting in artificial nest boxes. This means that the experts were able to regularly check the condition of the Chicks and the presence of parasites. In total, over two seasons, the watchers tracked the fate of 44 nests in 25 nest boxes.

The experiment confirmed that insecticide-treated iridescent feathers protect birds from the flies. The researchers found larvae in all control nests, and average number of parasites in the nest amounted to 32 individuals. However, among nests, the construction of which used the treated feathers, parasites were found in only three. Their average number was between 0.31 individuals. This directly affected the survival of offspring: if the control nests fledged a total of eight percent of young Chicks, in experimental this figure reached 95 per cent — even better than with manual spraying nests.

The researchers note that the provision of the birds insecticide-treated nesting material — a simple and inexpensive technique that can significantly improve the breeding success of rare species. It can be adapted for many other birds and mammals.

Specialists on nature protection are often criticized because they neglect the ecological role of parasites. Given this, the authors also emphasize that their proposed measures would not threaten the existence of endemic flies P. longicornis. The fact that these parasites live in the nests of four bird species, including the introduced to Tasmania house sparrows (Passer domesticus). Even if the flies will no longer be able to infect the nest of the Tasmanian rainbow birds, they are not threatened by extinction.

Some birds have found their own way to protect the nest from parasites. For example, living in the cities of the Mexican rosefinches (Carpodacus mexicanus) is added in the nests of cigarette butts. This allows them to protect themselves from ticks.

Sergey Knee High

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