The purple-crowned fairy wrens, tiny but striking Australian songbirds, could be at even greater risk from global warming after a study found that exposure to hot and dry conditions damages nestlings' genes.
The scientists found that the effect of global heating on species was silent, harmful and lifelong.
The wrens weigh less than 13 grams and live in pockets of dense vegetation along river systems.
The length of a part of the birds' DNA known as a telomere, which is a marker for how long they can reproduce, was affected by the temperature in the birds' habitat.
As the climate warms, the study said, the birds were likely to be exposed to more heat and shortening of the telomeres.
The change was revealed after scientists took blood samples from the birds in the sanctuary.
The shortening of the telomeres accelerated the aging process of birds because they died younger and had fewer offspring.
Climate models were looked at by Eastwood and his colleagues to see how the temperatures could change. He said that even under relatively mild climate warming scenarios that the non-lethal effects on nestling telomere length alone could lead to population decline.
The fairy wrens have been monitored for 17 years.
When the blood samples are analysed, nestlings are not much heavier than a pencil.
The findings were concerning according to Prof Anne Peters. She said that they need to be vigilant for the silent threats that can be uncovered.
She said that it was possible that natural selection could favour wrens with longer telomeres. It wasn't known if this could happen quickly or not.
As conditions get hotter, other species could be at risk as well.
She said there was never a single threat faced by a species.
She said that it was more difficult to prevent DNA damage caused by rising heat than it was to reduce those other threats.
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