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Early not always best

Will our mild winter bring the migrating songbirds back sooner than usual? Perhaps — but it’s difficult to predict how birds will react. Snowstorms in North and South Dakota may keep them from flying back to Manitoba, or an early thaw there may result in their arrival earlier than usual here.

But whether they return early or late, sudden changes in weather, or any extreme weather, can be deadly to returning birds. This is particularly true in spring for some of our early-returning songbirds, such as the bluebird.

Manitoba has two types of bluebirds — the eastern bluebird and the mountain bluebird, with the mountain variety historically located in the western half of the province, while the eastern variety has been farther east. Over the last number of years, however, the eastern variety has been steadily moving farther west. Records from the Friends of the Bluebirds Society — based in Brandon — show that over the last few years the two varieties are frequently overlapping. Fortunately, the records show a gradual return in bluebird populations, but last year’s records also showed the danger of weather extremes.

Bird lovers are always excited to see the first early arrivals, but sometimes coming early isn’t for the best. Last year a snowstorm with lots of wind occurred the last day of April, when about 20 to 30 centimetres of snow fell — with the resulting death of some songbirds. My husband had set out bluebird houses in April but was dismayed to find a pair of eastern bluebirds dead in one of his houses, after the bad weather. Whether they died of hypothermia or starved due to lack of insects, we couldn’t tell, but it was very disappointing. Other blue-birders reported losses, too. But they weren’t the only birds affected by the storm. Robins often are affected, and my husband discovered a dead hermit thrush on a nearby golf course shortly afterwards.

Following a snowstorm, or during a particularly cold spell, birders can act to help migrating birds. Shovel off a bare patch of grass, or create a sheltered feeder on the ground — for ground-feeding birds. Then put out various seeds and bread crumbs. This will give birds something to eat when natural food isn’t available. Returning birds that we fed at our backyard feeders last spring, after the storm, included fox sparrows, white-crowned and white-throated sparrows and juncos, among others. If you have saskatoon berries or chokecherries in your freezer, robins might be interested in those.

Extremes in summer can also prove deadly. Last summer on our route, nests of both bluebirds and tree swallows suffered. In some cases nests with eggs had been abandoned — perhaps because the parents had died. In others, young birds — several at a time — had died in the nest. This was after a particularly hot spell. Had the nest boxes proved too hot for the infant birds? Other birders described the same problem and attributed the deaths to the heat wave.

Research shows that prolonged excessive heat causes dehydration and heat stress, and that bluebird eggs and nestlings cannot survive temperatures higher than 41 C. If readers decide to make birdhouses, make sure the lumber is at least 3/4 inch thick, because the temperature inside the box may be several degrees higher than outside. (One-inch thickness is preferred, for better insulation against heat or cold.) A roof overhang will provide a little shade, and side slots or two to three holes of 3/4 inch each, at the top of the box, can provide some ventilation. Nest boxes should never be painted a dark colour, but left natural. Those who live in hot southern states sometimes use heat shields and screens. (For more exact information on various birdhouses, check the Internet.)

If you’re interested in birds and would like to get involved with the Friends of the Bluebirds, this year’s spring meeting is scheduled for April 15 at the Riverbank Discovery Centre in Brandon. For further information phone (204) 523-8258 or check out the Internet at http://www.mts.net/~jbdanard/about_us_friends.html.

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