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Heavy rain deadly for young falcons
Study conducted near Rankin Inlet found one-third of peregrine falcon deaths were caused by rain

Miranda Scotland
Northern News Services
Published Wednesday, December 11, 2013

Increased frequency of heavy rain in the Arctic is posing a serious threat to the survival of young peregrine falcons, according to a recent University of Alberta study.

Over the past three decades there has been a decline in reproductive success among falcon pairs nesting on the shores of Hudson Bay, near Rankin Inlet.

"We knew DDT was no longer an issue and based on field observations, we wondered whether changes in climate were responsible for high mortality in recent years," stated Alastair Franke, co-author of the study, in a news release.

Franke and colleagues from the Universite du Quebec decided to narrow their focus to the effect of heavy rain on nestlings after noting a pattern between peregrine reproduction and yearly precipitation values.

To test their hypothesis, researchers set up motion-sensitive cameras near nests and introduced wooden nest boxes to randomly selected pairs.

From 2008 to 2010, the team found more than one-third of young falcon deaths were caused by rain.

In one case, the mother bird knocked the nestling off a cliff ledge during a rainstorm.

Other nestlings drowned in their nest or died from hypothermia.

Meanwhile, chicks that lived in the nest boxes faired better during rainstorms. In fact, none of them died as a result of rainfall.

Young falcons are extremely susceptible to cold and wet weather in the first weeks of life because they aren't able to regulate their own temperature yet.

Plus, when their down feathers get wet they can't retain heat, said Franke in a phone interview with Nunavut News/North.

"If you were wearing a downfilled jacket ... if that's dry and fluffy it's very, very warm. But if you were to wet that jacket and the down inside becomes saturated, that down is no longer able to provide any insulative property," he said.

Starvation was another main factor in young falcon deaths. Fifteen per cent of deaths were directly attributed to a lack of food, while 31 per cent of deaths were a result of unconfirmed reasons, "though a combination of rainfall and starvation were suspected in" half the cases, according to the study.

Franke said he believes an increase in Arctic storms may be causing a reduction in the abundance of prey for peregrines and has launched a food supplementation study to test his belief.

Although peregrine falcon population numbers in Nunavut are currently high, both studies may prove helpful in maintaining the species in the future, said Franke.

"The important thing for us is to continue monitoring at multiple places, so we can give feedback to wildlife managers in terms of health and status of population."

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