Giving a hoot about the burrowing owl

Burrowing owls have disappeared over much of their historic range in North America.

In B.C., the burrowing owl used to make its home in the southern grasslands of B.C., from the U.S. border north to Lac Du Bois in the Kamloops area.

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The last nesting colony of six owl pairs at the Vernon Commonage had a city waste-spray irrigation project and a hybrid cottonwood research forest established on its last grassland stronghold.

Within a few years, nesting owls were completely gone from B.C.

The burrowing owl is one of the smallest of owls and smallest grassland raptor. Some adults weigh as much as 250 grams in the fall.

For their size, burrowing owls have a fierce countenance, certainly at least to their prey, which consist of rodents, insects, amphibians, small reptiles and small birds.

They may be active at any time during a day and are vulnerable to predation from mammals and other raptors.

Owl parents use burrows to nest in grassland colonies, laying from two to 12 eggs. The attrition rate of young can be high.

But, how did we lose this little owl?

Various reasons have been attributed to the loss and each are true.

The burrowing owl is the only one known to live underground; however, they are unable to dig the burrows required for nesting and escape.

They make use of deserted burrows, such as those excavated by marmots, ground squirrels, coyotes and badgers.

These burrows are frequently in short supply, as are B.C. grasslands.

About 95 per cent of those rare lands are also used by farmers and ranchers or have been converted to industrial or residential uses.

All land uses are not necessarily a negative activity, although ranching in the past has not been neighbourly toward some of grassland burrowing species like the coyote, marmot and badger.

Kamloops-area ranchers, such as Guichon, Haughton, Frolek and Deleeuw have co-operated to support owl recovery on their grasslands.

In some cases, they directed livestock grazing to owl nesting areas to facilitate reduction in grass height, improving owl hunting success and reducing cover for predators.

Another part of the answer as to what happened to the owls includes man’s successful efforts at fire suppression.

Natural fire cycles maintained open grasslands, encouraging early successions of plants, nutrient recycling and numerous small prey.

In turn, burrowing mammals were encouraged, and their abandoned burrows provided owls with nesting and escape locations.

Providing suitably placed and maintained artificial burrows is felt to be a major key in replacing one of the missing elements for recovery.

The agencies planning for owl recovery are the provincial government’s fish and wildlife branch and the Burrowing Owl Conservation Society of BC.

The reintroduction program began in the Kamloops area, from 1983 through 1986.

The current program began in the Lac Du Bois area in 1991 and has since grown to nine other locations.

Initially, owls for reintroduction were obtained from the Ontario Owl Rehabilitation Centre but now adult birds for release at recovery sites in the Kamloops area are reared in and obtained from the BC Wildlife Park.

Dave Low, an area fish and wildlife branch biologist, continued owl recovery efforts through retirement and was joined and assisted by members of the Kamloops and District Fish and Game Association.

Low focuses on the La Du Bois site and 68 nesting burrows have been placed and maintained there.

Other sites are managed by members of the Burrowing Owl Conservation Society.

It takes two to three club members about two hours to install a nesting burrow from prepared components.

Over many years, a workable design has developed using buried plastic nursery pots. Attached to them is a six- to eight-foot perforated drain pipe angled through the stony glacial tills to the surface, creating a burrow entrance to the pots.

The ground is armoured with large stones and the entrance area is cleared of brush and other predator cover for several feet around.

Nest-box maintenance is ongoing throughout the year but is best in the spring, when burrows and entrance tunnels are cleaned, which is what is happening at this time.

So far, one owl has returned to join the one that stayed all winter.

In the next two weeks, more males will arrive, establishing territories followed by the females.

The owls soon pair up, but not necessarily with a past acquaintance.

While the female nests, the male supplies hunted food.

Chicks are monitored and, if food supplies are low, their diet may be supplemented with captured mice or dead chicks from poultry farms.

Before chicks are out on their own, they are caught, weighed, checked by a vet for defects and banded for future identification.

In October, most maturing owls leave for warmer coastal climates, but some owls may remain over winter using food stored in the burrows.

If necessary, supplemental owl winter rations may be provided.

Information concerning movements of burrowing owls has resulted from years of leg banding for identification.

Leg banding has shown the little owl is mobile in travelling to southerly areas, where some choose to avoid harsh winter months.

One banded bird traveled almost 300 kilometres in a night.

Elsewhere, another flew from Arizona to southern Saskatchewan in two weeks.

In the past two decades, migrating burrowing owls from the Nicola and Thompson valleys have been identified at Portland, San Francisco, San Jose, on the coast of Washington state at Port Lincoln lighthouse on the Olympic Peninsula and numerous locations in the lower Fraser Valley.

The Lac du Bois recovery site is proving to be outstanding.

For their efforts, the club and, in particular, Dave Low, Bill Strom and Murray Jeffrey, were recently awarded the Roderick Haig Brown Conservation Award by the BC Wildlife Federation.

Last year, 29 young were produced, bringing to 143 the number of birds for the last five years.

Yet, comparing the numbers of juveniles produced, the number of owls returning in following years is very low.

Some juvenile bird destinations are known, but where are the majority going?

What is happening that so few birds return?

Good questions. There is still work to be done.

Geoff Swannel is a member of the Kamloops and District Fish and Game Association.

© Kamloops This Week

 


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