Snowy Owls in the Canadian Maritimes

From the end of November to December 15, 2008 the CCWHC received five Snowy Owls: three from Prince Edward Island and two from Nova Scotia. The birds submitted to the CCWHC had died of emaciation/starvation and in some cases weighed less than half of their normal body weight. Currently there is a snowy owl in rehabilitation at the Atlantic Veterinary College.

Several starving and dead snowy owls have been reported in the eastern provinces over the past month, suggesting that this is part of a much broader phenomenon. Others seem to be thriving in the Maritimes, like the owl that has been frequently sited by the bridge over the Hillsborough river between Charlottetown and Stratford, PEI (see article here). Snowy owls usually live year-round in the Arctic, but may occasionally migrate south in the winter, as seems to be the case this year.

In their Arctic home these big owls can catch ptarmigan, ducks, hares and other fairly large prey, but when opportunity presents itself, they prefer to feed on the cyclic and sometimes abundant lemming. This seem to be especially true for young birds that have not yet acquired the skills needed to catch the bigger, faster prey and therefore must rely heavily on lemmings once the parents stop feeding them.

It has been suggested that a crash in the population of mice and lemmings in the North is the likely reason why the owls are forced to migrate south. The migration we are witnessing could be a sign that this year will not be an easy one for the owls. All the birds that were received at CCWHC and had died of starvation were immature, their inexperience as hunters may have been a disadvantage if food was in short supply. This theory associating the crashes in lemming population with snowy owl migration to southern Canada has been repeatedly questioned, however. Migration south seems to occur in a 4-year-cycle, although it can also occur in 2 consecutive years. It has been difficult to match the lemming population numbers to the southern migration of owls: some years when the owls migrate the lemming population is high in the Arctic while other years when the owls choose to stay in the Arctic lemmings are not as abundant. Thus snowy owls’ southern visits remain somewhat of a mystery. The extent of snowy owl migration between breeding and wintering grounds is also poorly known. More radio transmitter studies will hopefully provide answers to the migration of this top predator of the Arctic.

Currently, researchers from Parks Canada and the Université Laval, Quebec, are working on migration and habitat of snowy owls in Nunavut.

By Fiep de Bie