Short-eared owl

This mysterious little raptor must contend with multiple threats to its survival including the absence of a recovery plan to help stabilize its populations

by Tim Tiner

Quiet, secretive and increasingly rare, the short-eared owl is an enigmatic, ground-nesting seeker of expansive open spaces. A bird that travels widely, it can be found on every continent, save Australia and Antarctica. In Canada, Asio flammeus could turn up anywhere south of the High Arctic, as long as the view is clear and the mousing is good. The owl’s nomadic ways, retiring manner and scant numbers, however, combine to limit the human understanding that may be needed to ensure this nocturnal hunter’s survival.

Like many other grassland birds, short-eared owls have been hard hit in recent decades. The intensification of agriculture, the disappearance of wetlands, development and recreation have sharply reduced their habitat over the past century. Pesticides may also be a threat. In southern Ontario, these graceful, crow-sized owls are now typically reported nesting in just a handful of sites each summer, usually in meadows, hayfields, pastures and marshes.

Cross-country surveys indicate that population numbers for this species fell by 23 percent over the past decade and by an average of 8 percent a year between 1968 and 2006. In 1994, the owl was officially designated as a species of special concern both federally and in Ontario. Although short-eared owl nests – bowls scraped into dead, matted vegetation – are well concealed in long grass, they are nevertheless often discovered by foxes, skunks, and other predators. Pressure from predators, however, probably increases in places where fields of grass are cut back or bisected with roads.

The nest locations of these owls change from one year to the next, fluctuating with the local abundance of voles. Short-ears pursue their tiny quarry by patrolling up and down fields like a northern harrier, gliding between slow wingbeats, usually two or three metres above the ground and often stopping to hover in mid-air. Their broad wings are very large for their body size, spanning a metre or more, and give the birds great buoyancy and an agile, bouncy manner of flight, often described as mothor butterfly-like. But their penchant for flying low also imperils them around roads.

While the Ontario Ministry of Natural Resources (MNR) has provided some research funding, it has no short-eared owl management plan, officially required for species of special concern. The ministry is scrabbling to draw up recovery plans for the 85 species designated as endangered and threatened in Ontario’s new Endangered Species Act.

This spring, the Committee on the Status of Endangered Wildlife in Canada reconfirmed the short-eared ranking, noting that it “nearly meets the criteria for threatened status.” Indeed, some biologists believe it definitely warrants a higher level of alert.

The owl’s status in Ontario remains unchanged largely because of a core nesting population in the Hudson Bay Lowlands that appears to be stable, though it has been too little studied to assess its status with certainty. Short-ears – almost absent in the forested interior of the province – are sometimes fairly common on the northern tundra and wetlands; aerial surveys by the Canadian Wildlife Service and MNR found their numbers dropped following rodent population crashes in the area in 2004 and 2005, but rose again by the summer of 2007.

Many people speculate that the threats to these birds increase in the winter when they are in more developed areas than their northern nesting strongholds. Southern Ontario has far more short-ears during the winter, when they sometimes begin hunting in the late afternoon, than in the nesting season. The Ottawa Valley lies at the northern limit of their winter range. Farther south, the Haldimand area sometimes hosts more of the owls than anywhere else on the continent, with 85 tallied on the 2003/04 Fisherville Christmas Bird Count, south of Cayuga. Most winter roosts – either on the ground in fields or, if the snow gets deep, in nearby evergreens – have only a few birds. Still, sightings have declined significantly as the owls’ old haunts have been turned into cornfields, subdivisions and other unsuitable settings.

To help fill the huge gaps in knowledge needed for effective conservation measures, the few researchers working on short-eared owls across North America have launched several satellite telemetry initiatives in the past two years. In February, Bird Studies Canada (bsc) attached a tiny, solar-powered backpack transmitter to a female owl wintering in Haldimand to track its movements. After flying to Michigan in April, the bird changed course and reached the tip of the Bruce Peninsula four days later, then flew all the way to the Ungava Peninsula in northwestern Quebec by mid-May, where apparently it settled down to nest.

Up to now, no one has even been sure whether the mysterious raptors have regular migration peaks and patterns. Both bsc and the Migration Research Foundation hope to get funding to outfit a few more short-ears with the transmitters in the coming winter.

Tim Tiner is the author of several books and is a frequent contributor to ON Nature.