An owl attacks the nest of a ferruginous hawk. (Photo contributed by Janet Ng)

Owls, raccoons threaten endangered hawk in surprising way

Medicine River Wildlife Centre helps ferruginous hawk research

The camera doesn’t lie.

University of Alberta researchers caught two unlikely predators in the act when they were studying the population decline of Alberta’s endangered ferruginous hawk.

While watching footage of nests, PhD candidate Janet Ng was shocked to learn great horned owls and raccoons were taking the young hawks from their nests in the wee dark hours of the morning.

The university’s Department of Biological Sciences said in a release that the discovery began when researchers found an empty nest that should have contained three hawk nestlings. When reviewing video, they realized that an owl attack in the nest had occurred.

A few weeks later, footage showed a raccoon in a different nest, removing nestlings from it and presumably eating them.

Researchers thought raccoons might attack young birds once they left the nest but they did not expect to see attacks in the nest itself, said Cameron Nordell, lead author on the study.

From 2011 to 2013, across 90 nests, the group recorded four attacks on nestlings — two by raccoons and two by owls. The attacks were between 3 and 4 a.m., when these nocturnal predators are most active and the hawks may be less wary or less able to defend against intruders.

The research team is concerned that high numbers of owls and raccoons around farms and other human settlements might pose a risk to many nestling ferruginous hawks, a threatened species in Canada. When constructing new platforms, risk to hawks can be reduced by placing platforms away from known owl nests and can include deterrents that prevent raccoons from climbing into nests.

Carol Kelly, executive director of the Medicine River Wildlife Centre, said these hawks inhabit prairie areas in eastern and southern Alberta, rather than parkland, so they are not found in Central Alberta.

However, she has treated numerous injured ferruginous hawks that have been brought in from other parts of Alberta and has had one at the centre for about 10 years.

It was found with a broken wing that had healed improperly before they received it, and nothing more could be done for it. Now it’s a companion bird for other injured hawks at the rehab centre.

The hawks are called ferruginous because ferrugo in Latin means rust — the colour of the back feathers of the large hawks. Their population decline is attributed largely to declining prairie habitat.

Kelly said the centre has been helping in a small way with research on the hawks.

Researchers want to capture the birds and put transmitters on them. They do this with a big outdoor cage with a great horned owl in it. When the hawks see the owls in their territory, they come down to chase it away, and are caught in a net. Transmitters are placed on them and they are released.

The Medicine River Wildlife Centre provides the live decoy owls as they have a few non-releasable ones.

Researchers used the cage and decoy owl already this year for a week and caught three of the hawks, Kelly said. The owls are not harmed.

barr@reddeeradvocate.com

 


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