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September/October 2000 issue

TO JUDGE FROM THE PICTURES in the field guide, the blackpoll warbler is drab, a small brownish bird streaked with white and black that is distinguished during the breeding season by the male’s dark cap. But the little creature lying quietly in Jul Wojnowski’s hand is far from nondescript. Its black cap glistens; its beak gleams needle-sharp; its round eyes are bright with awareness.

For Wojnowski, being eye to eye with a warbler is all in a day’s work. As chief bander at the Lesser Slave Lake Bird Observatory in north-central Alberta and, before that, at a similar centre at Long Point on Lake Erie, he has handled thousands of songbirds. Yet despite this familiarity, Wojnowski remains astonished by the life he holds in his hands. “The birds we intercept at the observatories are on a mission,” he says. “What they are doing is awe-inspiring.”

Like many other songbirds that nest in the boreal forest, the blackpoll warbler is a long-distance migrant. In the fall, its mission is to travel 20,000 kilometres from northern Canada to southern Brazil, a journey that includes a three-day non-stop flight over the ocean. Come spring, it will make this epic voyage in reverse, as the tide of birdlife flows back toward Canada’s northernmost forest.

The purpose of the observatories is to sample this migratory flood as it surges north and south, to assess the populations of blackpolls and of more than 100 other bird species. The information gathered by Wojnowski at Lesser Slave Lake, and by others at Long Point and 13 other stations across Canada, is then forwarded to the fledgling Canadian Migration Monitoring Network.

The research protocol of the network could be summarized as “catch and release.” Every morning from April to mid-June and again from mid-July to October, Wojnowski and his counterparts across the country set up their mist nets before dawn. (Think of large, rectangular hairnets erected on poles.) As migrating birds drop down into the woods to feed after a long night’s flight, a few fly into these obstacles and come to a sudden halt. Skilled hands immediately go to work, gently disentangling them from the nets and fitting each individual with a numbered leg band. Data are entered for every capture — species, age, sex, band number, and so on — and in a matter of minutes, the bird is set free to continue on its travels.

At Lesser Slave Lake, this routine will be repeated about 5,000 times this year. Across the entire network, the total will be more than 60,000 birds. Since the counts in any one season are affected by weather and other variables, this effort must be sustained for at least 10 years before long-term trends can be teased out of the data.

This is a prodigious commitment, but one that is necessary to address a gaping hole in our knowledge. Without migration monitoring, we would know virtually nothing about what is happening to the birds that nest in the boreal forest. In the past, the main tool for tracking songbird populations has been an annual bird-counting bee called the Breeding Bird Survey (BBS). Now entering its thirty-fifth year, the BBS deploys a small army of birders to drive along country roads in southern Canada and the United States and record their observations. But where the grid roads come to an end, so does the BBS — an omission that encompasses most of the boreal forest and about one-sixth of North American birds. As logging and other industries expand into the boreal forest, so does the potential for harm. “We are the biggest factor affecting these species and their habitats,” Wojnowski says. “Ultimately, it’s our responsibility to ensure that we don’t cause populations to become threatened or go extinct.”

FOR THE MOMENT, our knowledge is hazy, but the picture will come into sharper focus over the coming years, as the stations in the network continue their research. Several are faced with a backlog of records that must be computerized; others, like the six-year-old Lesser Slave Lake observatory, are patiently extending their data collection so the numbers can be analyzed. At present, only the Long Point observatory, which dates back four decades, has a long enough string of data to provide trustworthy results.

These early indications are surprisingly positive. Since the 1970s and 1980s, when many species of warblers suffered sharp declines, the counts at Long Point have been on a steady rise. Of the 20 tropical-wintering warblers noted at the observatory, 14 (including the dapper blackpoll) have increased significantly over the past 10 years. Several others — the Tennessee, bay-breasted, Cape May and Blackburnian warblers — are currently depressed, but this is probably the result of cyclic variations in their preferred food, the spruce budworm. Sadly, there is no easy explanation for the declines of the ovenbird, wood thrush and veery, all of which appear to be ever-so-gradually disappearing.

Charles Francis, senior scientist and statistician for the Migration Monitoring Network, warns against putting too much stock in these preliminary results. "I don’t think we have enough data yet to be sure we know what is going on," he cautions. He looks forward to the day when all the stations are fully on board, and their results can be compared and interpreted. But the speed with which this will happen depends, in part, on the availability of funds, which must be pieced together, station by station, year by year, from contracts, grants and private donations. "Funding is always a challenge," says Francis.

Yet one way or another, that challenge is being met. If bird migration is a miracle, the creation of the Migration Monitoring Network is a small miracle in itself. The future of our boreal-forest avian migrants has fallen into good hands.

For more information on the Lesser Slave Lake Bird Observatory, visit its website at www.lslbo.org. The Migration Monitoring Network is at www.bsc-eoc.org/volunteer/cmmn/.

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