Excessive Rainfall is Killing Peregrine Falcons in Canada

Peregrine falcons in the Canadian Arctic are suffering due to a surge in precipitation, according to a new study from two Canadian universities.

While rainfall is typically a boon - sustaining life and supporting plant growth across the Earth - an excess of it in northern Canada brought on by warmer summer temperatures is, according to the researchers, posing the greatest threat to peregrine falcons since the pesticide DDT.

Research co-author Alastair Franke of the University of Alberta and his colleagues from the University of Quebec contend that gradual changes in Arctic temperature and increases in rainfall are linked to long-term declines in the reproduction rate of the peregrine.

With historical weather data and more than 30 years of breeding data at their disposal, the researchers set up an experiment near Rankin Inlet in Nunavut province on the shores of the Hudson Bay, where a dense population of peregrine falcons is known to exist. Franke and his colleagues monitored the falcons' nests for two years using motion-sensing cameras.

The resulting data confirmed their suspicions. More than one-third of the falcon chicks observed died from rain. The researchers found this to be consistent whether the chicks were raised in nestboxes or on natural ledges.

"The nestlings died from hypothermia and in some cases from drowning in their flooded nests. Without constant parental care, they are most vulnerable to cold and wet conditions in the first three weeks of life," Franke said.

The investigation into the falcon deaths came after researchers realized that there was still a marked population decline even after the pesticide DDT was banned in 1970. DDT residues were linked to reproductive failure in peregrines.

"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," Franke said.

In addition to drowning and hypothermia, Franke also observed falcon chicks starving to death.

"We were surprised to find that a considerable number of nestlings raised in nestboxes later died of starvation despite having been spared from the direct effects of rain," he said.