Study shows wires, cars and lead are killing many Maritime bald eagles

A study of how humans are contributing to bald eagle deaths has found Maritimers could be doing a better job of protecting the birds.

Pierre-Yves Daoust, a wildlife pathologist and professor emeritus at the Atlantic Veterinary College in Charlottetown, and his co-authors collated the results of 426 incidents brought to the college’s attention over the last 26 years.

“We thought it was very important to put all this information together for biologists [and] conservation officers to be aware of the main causes of mortality,” Daoust told Island Morning host Mitch Cormier.

This kind of study has been done elsewhere around North America and the results in the Maritimes were not that different, he noted.

Some causes of mortality in bald eagles are difficult to avoid, says Pierre-Yves Daoust. (CBC)

“Human causes of mortality are mainly responsible for the death of those bald eagles,” said Daoust.

Some of the most common causes of death among the eagles are likely unavoidable — for example, electrocution from the birds coming into contact with power lines, the cause of death in 11 per cent of the cases studied.

As well, bald eagles put themselves into danger because they are opportunistic scavengers.

“One of the more common causes of mortality was collisions with vehicles because they were trying to benefit from road kill,” said Daoust.

This map from the study Daoust co-authored with Amélie Mathieu, E. Jane Parmley, Scott McBurney, Colin Robertson and Helene Van Doninc shows the site where bald eagle deaths were reported throughout the Maritimes. (Paper in Canadian Wildlife Biology and Management)

A total of 14 per cent of the deaths came when eagles were scavenging on a roadway. “Of course that’s not a good place to be spending too much time.”

Other problems are more solvable, he said — in particular, lead poisoning that is another outcome of the eagles’ scavenging behaviour, cited in 9 per cent of the deaths. 

Lead shot from hunting can be left behind in unwanted parts of carcasses, and the birds ingest it while feeding. Anglers using lead sinkers for fishing are also a problem. Fish can eat sinkers that get lost on the bottom of rivers and lakes, and fish are another important food source for bald eagles.

“The use of lead ammunition has been banned for hunting water fowl, but people still use lead sinkers when they go fishing, they still use lead ammunition when they go hunting,” said Daoust.

Bald eagle populations are growing on P.E.I., following decades of very low numbers with only one or two known nests. (CBC)

“[Eagles] do not need to ingest much of this lead to die.”

Other human-related causes of death include trapping, snaring and gunshot.

“At least some cases of trauma of unknown cause and some unknown causes of death may have also involved anthropogenic factors,” the study notes. 

Bald eagles are not a species at risk in Canada, and their numbers are growing on P.E.I., Daoust added. They tend to congregate on Island shorelines and rivers where fish are plentiful.

A bald eagle held in captivity can live up to 50 years, according to a paper prepared for the P.E.I. government in 1999, but lifespans in the wild are much lower, with the highest amount of danger coming in an eagle’s early years. 

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